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Malinowski R, Singh D, Kasprzewska A, Blicharz S, Basińska-Barczak A. Vascular tissue - boon or bane? How pathogens usurp long-distance transport in plants and the defence mechanisms deployed to counteract them. THE NEW PHYTOLOGIST 2024. [PMID: 39101283 DOI: 10.1111/nph.20030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Accepted: 06/13/2024] [Indexed: 08/06/2024]
Abstract
Evolutionary emergence of specialised vascular tissues has enabled plants to coordinate their growth and adjust to unfavourable external conditions. Whilst holding a pivotal role in long-distance transport, both xylem and phloem can be encroached on by various biotic factors for systemic invasion and hijacking of nutrients. Therefore, a complete understanding of the strategies deployed by plants against such pathogens to restrict their entry and establishment within plant tissues, is of key importance for the future development of disease-tolerant crops. In this review, we aim to describe how microorganisms exploit the plant vascular system as a route for gaining access and control of different host tissues and metabolic pathways. Highlighting several biological examples, we detail the wide range of host responses triggered to prevent or hinder vascular colonisation and effectively minimise damage upon biotic invasions.
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Affiliation(s)
- Robert Malinowski
- Department of Integrative Plant Biology, Institute of Plant Genetics of the Polish Academy of Sciences, ul. Strzeszynska 34, Poznań, 60-479, Poland
| | - Deeksha Singh
- Department of Integrative Plant Biology, Institute of Plant Genetics of the Polish Academy of Sciences, ul. Strzeszynska 34, Poznań, 60-479, Poland
| | - Anna Kasprzewska
- Regulation of Gene Expression Team, Institute of Plant Genetics of the Polish Academy of Sciences, ul. Strzeszynska 34, Poznań, 60-479, Poland
| | - Sara Blicharz
- Department of Integrative Plant Biology, Institute of Plant Genetics of the Polish Academy of Sciences, ul. Strzeszynska 34, Poznań, 60-479, Poland
| | - Aneta Basińska-Barczak
- Department of Integrative Plant Biology, Institute of Plant Genetics of the Polish Academy of Sciences, ul. Strzeszynska 34, Poznań, 60-479, Poland
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Xie L, Zeng X, Amir MB, Zou X, Yuan J, Yu H, Lu Z, Chen W. Clathrin heavy chain is involved in infection of Candidatus Liberibacter asiaticus in the host vector Diaphorina citri. INSECT SCIENCE 2024; 31:1326-1332. [PMID: 38093436 DOI: 10.1111/1744-7917.13305] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 10/22/2023] [Accepted: 11/13/2023] [Indexed: 08/14/2024]
Affiliation(s)
- Lianjie Xie
- National Navel Orange Engineering Research Center, School of Life Sciences, Gannan Normal University, Ganzhou, Jiangxi Province, China
| | - Xiangdong Zeng
- National Navel Orange Engineering Research Center, School of Life Sciences, Gannan Normal University, Ganzhou, Jiangxi Province, China
| | - Muhammad Bilal Amir
- National Navel Orange Engineering Research Center, School of Life Sciences, Gannan Normal University, Ganzhou, Jiangxi Province, China
- South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
| | - Xiaojin Zou
- National Navel Orange Engineering Research Center, School of Life Sciences, Gannan Normal University, Ganzhou, Jiangxi Province, China
| | - Jingfu Yuan
- Agriculture and Rural Affairs Office of Datangbu Town, Ganzhou, Jiangxi Province, China
| | - Haizhong Yu
- National Navel Orange Engineering Research Center, School of Life Sciences, Gannan Normal University, Ganzhou, Jiangxi Province, China
| | - Zhanjun Lu
- National Navel Orange Engineering Research Center, School of Life Sciences, Gannan Normal University, Ganzhou, Jiangxi Province, China
| | - Wei Chen
- National Navel Orange Engineering Research Center, School of Life Sciences, Gannan Normal University, Ganzhou, Jiangxi Province, China
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Singh K, Huff M, Liu J, Park JW, Rickman T, Keremane M, Krueger RR, Kunta M, Roose ML, Dardick C, Staton M, Ramadugu C. Chromosome-Scale, De Novo, Phased Genome Assemblies of Three Australian Limes: Citrus australasica, C. inodora, and C. glauca. PLANTS (BASEL, SWITZERLAND) 2024; 13:1460. [PMID: 38891269 PMCID: PMC11174732 DOI: 10.3390/plants13111460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/14/2024] [Accepted: 05/20/2024] [Indexed: 06/21/2024]
Abstract
Huanglongbing (HLB) is a severe citrus disease worldwide. Wild Australian limes like Citrus australasica, C. inodora, and C. glauca possess beneficial HLB resistance traits. Individual trees of the three taxa were extensively used in a breeding program for over a decade to introgress resistance traits into commercial-quality citrus germplasm. We generated high-quality, phased, de novo genome assemblies of the three Australian limes using PacBio long-read sequencing. The genome assembly sizes of the primary and alternate haplotypes were determined for C. australasica (337 Mb/335 Mb), C. inodora (304 Mb/299 Mb), and C. glauca (376 Mb/379 Mb). The nine chromosome-scale scaffolds included 86-91% of the genome sequences generated. The integrity and completeness of the assembled genomes were estimated to be at 97.2-98.8%. Gene annotation studies identified 25,461 genes in C. australasica, 27,665 in C. inodora, and 30,067 in C. glauca. Genes belonging to 118 orthogroups were specific to Australian lime genomes compared to other citrus genomes analyzed. Significantly fewer canonical resistance (R) genes were found in C. inodora and C. glauca (319 and 449, respectively) compared to C. australasica (576), C. clementina (579), and C. sinensis (651). Similar patterns were observed for other gene families associated with potential HLB resistance, including Phloem protein 2 (PP2) and Callose synthase (CalS) genes predicted in the Australian lime genomes. The genomic information on Australian limes developed in the present study will help understand the genetic basis of HLB resistance.
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Affiliation(s)
- Khushwant Singh
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA; (K.S.); (M.L.R.)
| | - Matthew Huff
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (M.H.); (T.R.); (M.S.)
| | - Jianyang Liu
- Innovative Fruit Production, Improvement, and Protection, Appalachian Fruit Research Station, USDA-ARS, Kearneysville, WV 25430, USA; (J.L.); (C.D.)
| | - Jong-Won Park
- Citrus Center, Texas A&M University-Kingsville, Weslaco, TX 78599, USA; (J.-W.P.); (M.K.)
| | - Tara Rickman
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (M.H.); (T.R.); (M.S.)
| | - Manjunath Keremane
- National Clonal Germplasm Repository for Citrus and Dates, USDA-ARS, Riverside, CA 92507, USA; (M.K.); (R.R.K.)
| | - Robert R. Krueger
- National Clonal Germplasm Repository for Citrus and Dates, USDA-ARS, Riverside, CA 92507, USA; (M.K.); (R.R.K.)
| | - Madhurababu Kunta
- Citrus Center, Texas A&M University-Kingsville, Weslaco, TX 78599, USA; (J.-W.P.); (M.K.)
| | - Mikeal L. Roose
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA; (K.S.); (M.L.R.)
| | - Chris Dardick
- Innovative Fruit Production, Improvement, and Protection, Appalachian Fruit Research Station, USDA-ARS, Kearneysville, WV 25430, USA; (J.L.); (C.D.)
| | - Margaret Staton
- Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN 37996, USA; (M.H.); (T.R.); (M.S.)
| | - Chandrika Ramadugu
- Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA; (K.S.); (M.L.R.)
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Robledo J, Welker S, Shtein I, Bernardini C, Vincent C, Levy A. Phloem and Xylem Responses Are Both Implicated in Huanglongbing Tolerance of Sugar Belle. PHYTOPATHOLOGY 2024; 114:441-453. [PMID: 37551959 DOI: 10.1094/phyto-05-23-0148-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/09/2023]
Abstract
Although huanglongbing (HLB) is a devastating citrus disease, improved tolerant cultivars, such as Sugar Belle (SB) mandarin, have been identified. To understand the responses that HLB-affected SB undergoes, we compared 14CO2 fixation, carbohydrate export, phloem callose accumulation, relative expression of plant defense activators, and anatomical changes between healthy and infected SB trees versus susceptible Pineapple (PA) sweet orange. Eight- to ten-week-old leaves of infected SB showed a 2.5-fold increase in 14CO2 fixation and a 13% decrease in 14C-carbohydrate export, whereas HLB-affected PA presented a decrease of 33 and 50%, respectively. The mean distance of a callose deposit to its closest neighbor was 36% smaller in infected SB versus healthy, whereas in HLB-affected PA, it was 33% higher. Expression of papain-like cysteine proteases (PLCPs) was upregulated in SB but downregulated in PA. Infected SB showed minor alterations in the number of xylem vessels, a 16% larger xylem vessel lumen area, and a 14% increase in the proportional area of the xylem. In contrast, PA showed a 2.4-fold increase in the xylem vessel number and a 2% increase in the proportional xylem area. Three complementary mechanisms of tolerance in SB are hypothesized: (i) increased carbohydrate availability induced by greater CO2 fixation, mild effect in carbohydrate export, and local accumulation of callose in the phloem; (ii) activation of defense response via upregulation of PLCPs, and (iii) increased investment in the xylem structure. Thus, phloem and xylem modifications seem to be involved in SB tolerance.
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Affiliation(s)
- Jacobo Robledo
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, U.S.A
| | - Stacy Welker
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Ilana Shtein
- Eastern Region Research and Development Center, Ariel, Israel
| | - Chiara Bernardini
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Christopher Vincent
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
- Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, U.S.A
| | - Amit Levy
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, U.S.A
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, U.S.A
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Makam SN, Setamou M, Alabi OJ, Day W, Cromey D, Nwugo C. Mitigation of Huanglongbing: Implications of a Biologically Enhanced Nutritional Program on Yield, Pathogen Localization, and Host Gene Expression Profiles. PLANT DISEASE 2023; 107:3996-4009. [PMID: 37415358 DOI: 10.1094/pdis-10-22-2336-re] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/08/2023]
Abstract
Huanglongbing (HLB, citrus greening disease), the most destructive disease affecting citrus production, is primarily linked to the gram-negative, insect-vectored, phloem-inhabiting α-proteobacterium 'Candidatus Liberibacter asiaticus' (CLas). With no effective treatment available, management strategies have largely focused on the use of insecticides in addition to the destruction of infected trees, which are environmentally hazardous and cost-prohibitive for growers, respectively. A major limitation to combating HLB is the inability to isolate CLas in axenic culture, which hinders in vitro studies and creates a need for robust in situ CLas detection and visualization methods. The aim of this study was to investigate the efficacy of a nutritional program-based approach for HLB treatment, and to explore the effectiveness of an enhanced immunodetection method to detect CLas-infected tissues. To achieve this, four different biologically enhanced nutritional programs (bENPs; P1, P2, P3, and P4) were tested on CLas-infected citrus trees. Structured illumination microscopy preceded by a modified immunolabeling process and transmission electron microscopy were used to show treatment-dependent reduction of CLas cells in phloem tissues. No sieve pore plugging was seen in the leaves of P2 trees. This was accompanied by an 80% annual increase in fruit number per tree and 1,503 (611 upregulated and 892 downregulated) differentially expressed genes. These included an MLRQ subunit gene, UDP-glucose transferase, and genes associated with the alpha-amino linolenic acid metabolism pathway in P2 trees. Taken together, the results highlight a major role for bENPs as a viable, sustainable, and cost effective option for HLB management.
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Affiliation(s)
- Srinivas N Makam
- Integrated Life Science Research Center (ILSRC), Goodyear, AZ 85338
| | - Mamoudou Setamou
- Texas A&M University-Kingsville Citrus Center, Weslaco, TX 78599
| | - Olufemi J Alabi
- Plant Pathology and Microbiology, Texas A&M AgriLife Research and Extension Center, Weslaco, TX 78596
| | - William Day
- The Imaging Cores Life Sciences North, Research, Innovation and Impact Department, University of Arizona, Tucson, AZ 85719
| | - Douglas Cromey
- The Imaging Cores Life Sciences North, Research, Innovation and Impact Department, University of Arizona, Tucson, AZ 85719
| | - Chika Nwugo
- Integrated Life Science Research Center (ILSRC), Goodyear, AZ 85338
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Ebert TA, Shawer D, Brlansky RH, Rogers ME. Seasonal Patterns in the Frequency of Candidatus Liberibacter Asiaticus in Populations of Diaphorina citri (Hemiptera: Psyllidae) in Florida. INSECTS 2023; 14:756. [PMID: 37754724 PMCID: PMC10532026 DOI: 10.3390/insects14090756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Revised: 09/04/2023] [Accepted: 09/06/2023] [Indexed: 09/28/2023]
Abstract
Candidatus Liberibacter asiaticus (CLas) is one of the putative causal agents of huanglongbing, which is a serious disease in citrus production. The pathogen is transmitted by Diaphorina citri Kuwayama (Hemiptera: Psyllidae). As an observational study, six groves in central Florida and one grove at the southern tip of Florida were sampled monthly from January 2008 through February 2012 (50 months). The collected psyllids were sorted by sex and abdominal color. Disease prevalence in adults peaked in November, with a minor peak in February. Gray/brown females had the highest prevalence, and blue/green individuals of either sex had the lowest prevalence. CLas prevalence in blue/green females was highly correlated with the prevalence in other sexes and colors. Thus, the underlying causes for seasonal fluctuations in prevalence operated in a similar fashion for all psyllids. The pattern was caused by larger nymphs displacing smaller ones from the optimal feeding sites and immunological robustness in different sex-color morphotypes. Alternative hypotheses were also considered. Improving our understanding of biological interactions and how to sample them will improve management decisions. We agree with other authors that psyllid management is critical year-round.
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Affiliation(s)
- Timothy A. Ebert
- Citrus Research and Education Center, University of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850, USA; (R.H.B.); (M.E.R.)
| | - Dalia Shawer
- Department of Economic Entomology, Faculty of Agriculture, Kafr Elsheikh University, Kafr Elsheikh 33516, Egypt;
| | - Ron H. Brlansky
- Citrus Research and Education Center, University of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850, USA; (R.H.B.); (M.E.R.)
| | - Michael E. Rogers
- Citrus Research and Education Center, University of Florida, 700 Experiment Station Rd., Lake Alfred, FL 33850, USA; (R.H.B.); (M.E.R.)
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7
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Pandey SS, Xu J, Achor DS, Li J, Wang N. Microscopic and Transcriptomic Analyses of Early Events Triggered by ' Candidatus Liberibacter asiaticus' in Young Flushes of Huanglongbing-Positive Citrus Trees. PHYTOPATHOLOGY 2023; 113:985-997. [PMID: 36449527 DOI: 10.1094/phyto-10-22-0360-r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
'Candidatus Liberibacter asiaticus' (CLas) is associated with the devastating citrus disease Huanglongbing (HLB). Young flushes are the center of the HLB pathosystem due to their roles in the psyllid life cycle and in the acquisition and transmission of CLas. However, the early events of CLas infection and how CLas modulates young flush physiology remain poorly understood. Here, transmission electron microscopy analysis showed that the mean diameter of the sieve pores decreased in young leaves of HLB-positive trees after CLas infection, consistent with CLas-triggered callose deposition. RNA-seq-based global expression analysis of young leaves of HLB-positive sweet orange with (CLas-Pos) and without (CLas-Neg) detectable CLas demonstrated a significant impact on gene expression in young leaves, including on the expression of genes involved in host immunity, stress response, and plant hormone biosynthesis and signaling. CLas-Pos and CLas-Neg expression data displayed distinct patterns. The number of upregulated genes was higher than that of the downregulated genes in CLas-Pos for plant-pathogen interactions, glutathione metabolism, peroxisome, and calcium signaling, which are commonly associated with pathogen infections, compared with the healthy control. On the contrary, the number of upregulated genes was lower than that of the downregulated genes in CLas-Neg for genes involved in plant-pathogen interactions and peroxisome biogenesis/metabolism. Additionally, a time-course quantitative reverse transcription-PCR-based expression analysis visualized the induced expression of companion cell-specific genes, phloem protein 2 genes, and sucrose transport genes in young flushes triggered by CLas. This study advances our understanding of early events during CLas infection of citrus young flushes.
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Affiliation(s)
- Sheo Shankar Pandey
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Jin Xu
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Diann S Achor
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Jinyun Li
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL 33850
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Estrella-Maldonado H, González-Cruz C, Matilde-Hernández C, Adame-García J, Santamaría JM, Santillán-Mendoza R, Flores-de la Rosa FR. Insights into the Molecular Basis of Huanglongbing Tolerance in Persian Lime ( Citrus latifolia Tan.) through a Transcriptomic Approach. Int J Mol Sci 2023; 24:ijms24087497. [PMID: 37108662 PMCID: PMC10144405 DOI: 10.3390/ijms24087497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 04/14/2023] [Accepted: 04/17/2023] [Indexed: 04/29/2023] Open
Abstract
Huanglongbing (HLB) is a vascular disease of Citrus caused by three species of the α-proteobacteria "Candidatus Liberibacter", with "Candidatus Liberibacter asiaticus" (CLas) being the most widespread and the one causing significant economic losses in citrus-producing regions worldwide. However, Persian lime (Citrus latifolia Tanaka) has shown tolerance to the disease. To understand the molecular mechanisms of this tolerance, transcriptomic analysis of HLB was performed using asymptomatic and symptomatic leaves. RNA-Seq analysis revealed 652 differentially expressed genes (DEGs) in response to CLas infection, of which 457 were upregulated and 195 were downregulated. KEGG analysis revealed that after CLas infection, some DEGs were present in the plant-pathogen interaction and in the starch and sucrose metabolism pathways. DEGs present in the plant-pathogen interaction pathway suggests that tolerance against HLB in Persian lime could be mediated, at least partly, by the ClRSP2 and ClHSP90 genes. Previous reports documented that RSP2 and HSP90 showed low expression in susceptible citrus genotypes. Regarding the starch and sucrose metabolism pathways, some genes were identified as being related to the imbalance of starch accumulation. On the other hand, eight biotic stress-related genes were selected for further RT-qPCR analysis to validate our results. RT-qPCR results confirmed that symptomatic HLB leaves had high relative expression levels of the ClPR1, ClNFP, ClDR27, and ClSRK genes, whereas the ClHSL1, ClRPP13, ClPDR1, and ClNAC genes were expressed at lower levels than those from HLB asymptomatic leaves. Taken together, the present transcriptomic analysis contributes to the understanding of the CLas-Persian lime interaction in its natural environment and may set the basis for developing strategies for the integrated management of this important Citrus disease through the identification of blanks for genetic improvement.
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Affiliation(s)
- Humberto Estrella-Maldonado
- Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Campo Experimental Ixtacuaco, Km 4.5 Carretera Martínez de la Torre-Tlapacoyan, Cong. Javier Rojo Gómez, Tlapacoyan C.P. 93600, Veracruz, Mexico
| | - Carlos González-Cruz
- Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Campo Experimental Ixtacuaco, Km 4.5 Carretera Martínez de la Torre-Tlapacoyan, Cong. Javier Rojo Gómez, Tlapacoyan C.P. 93600, Veracruz, Mexico
| | - Cristian Matilde-Hernández
- Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Campo Experimental Ixtacuaco, Km 4.5 Carretera Martínez de la Torre-Tlapacoyan, Cong. Javier Rojo Gómez, Tlapacoyan C.P. 93600, Veracruz, Mexico
| | - Jacel Adame-García
- Tecnológico Nacional de México, Campus Úrsulo Galván, Km 4.5 Carretera Cd. Cardel-Chachalacas, Úrsulo Galván C.P. 91667, Veracruz, Mexico
| | - Jorge M Santamaría
- Centro de Investigación Científica de Yucatán A.C., Calle 43 No. 130, Colonia Chuburná de Hidalgo, Mérida C.P. 97205, Yucatán, Mexico
| | - Ricardo Santillán-Mendoza
- Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Campo Experimental Ixtacuaco, Km 4.5 Carretera Martínez de la Torre-Tlapacoyan, Cong. Javier Rojo Gómez, Tlapacoyan C.P. 93600, Veracruz, Mexico
| | - Felipe Roberto Flores-de la Rosa
- Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias (INIFAP), Campo Experimental Ixtacuaco, Km 4.5 Carretera Martínez de la Torre-Tlapacoyan, Cong. Javier Rojo Gómez, Tlapacoyan C.P. 93600, Veracruz, Mexico
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9
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Wen G, Xie Z, Yang Y, Yang Y, Guo Q, Liang G, Dang J. NpPP2-B10, an F-Box-Nictaba Gene, Promotes Plant Growth and Resistance to Black Shank Disease Incited by Phytophthora nicotianae in Nicotiana tabacum. Int J Mol Sci 2023; 24:ijms24087353. [PMID: 37108517 PMCID: PMC10138871 DOI: 10.3390/ijms24087353] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Revised: 04/09/2023] [Accepted: 04/11/2023] [Indexed: 04/29/2023] Open
Abstract
Black shank, a devastating disease affecting tobacco production worldwide, is caused by Phytophthora nicotianae. However, few genes related to Phytophthora resistance have been reported in tobacco. Here, we identified NpPP2-B10, a gene strongly induced by P. nicotianae race 0, with a conserved F-box motif and Nictaba (tobacco lectin) domain, in the highly resistant tobacco species Nicotiana plumbaginifolia. NpPP2-B10 is a typical F-box-Nictaba gene. When it was transferred into the black shank-susceptible tobacco cultivar 'Honghua Dajinyuan', it was found to promote resistance to black shank disease. NpPP2-B10 was induced by salicylic acid, and some resistance-related genes (NtPR1, NtPR2, NtCHN50, and NtPAL) and resistance-related enzymes (catalase and peroxidase) were significantly upregulated in the overexpression lines after infection with P. nicotianae. Furthermore, we showed that NpPP2-B10 actively regulated the tobacco seed germination rate, growth rate, and plant height. The erythrocyte coagulation test of purified NpPP2-B10 protein showed that NpPP2-B10 had plant lectin activity, and the lectin content in the overexpression lines was significantly higher than that in the WT, which could lead to accelerated growth and improved resistance of tobacco. SKP1 is an adaptor protein of the E3 ubiquitin ligase SKP1, Cullin, F-box (SCF) complex. We demonstrated that NpPP2-B10 could interact with the NpSKP1-1A gene in vivo and in vitro through yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC), indicating that NpPP2-B10 likely participates in the plant immune response by mediating the ubiquitin protease pathway. In conclusion, our study provides some important insights concerning NpPP2-B10-mediated regulation of tobacco growth and resistance.
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Affiliation(s)
- Guo Wen
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715, China
- Academy of Agricultural Sciences of Southwest University, State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
- College of Horticulture, China Agricultural University, Beijing 100193, China
| | - Zhongyi Xie
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715, China
- Academy of Agricultural Sciences of Southwest University, State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
- College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yao Yang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715, China
- Academy of Agricultural Sciences of Southwest University, State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
| | - Yuxue Yang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715, China
- Academy of Agricultural Sciences of Southwest University, State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
| | - Qigao Guo
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715, China
- Academy of Agricultural Sciences of Southwest University, State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
| | - Guolu Liang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715, China
- Academy of Agricultural Sciences of Southwest University, State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
| | - Jiangbo Dang
- Key Laboratory of Horticulture Science for Southern Mountains Regions of Ministry of Education, College of Horticulture and Landscape Architecture, Southwest University, Chongqing 400715, China
- Academy of Agricultural Sciences of Southwest University, State Cultivation Base of Crop Stress Biology for Southern Mountainous Land of Southwest University, Chongqing 400715, China
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10
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Current Epidemic Situation and Control Status of Citrus Huanglongbing in Guangdong China: The Space–Time Pattern Analysis of Specific Orchards. Life (Basel) 2023; 13:life13030749. [PMID: 36983905 PMCID: PMC10055705 DOI: 10.3390/life13030749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/04/2023] [Accepted: 03/05/2023] [Indexed: 03/12/2023] Open
Abstract
Huanglongbing (HLB) is the most harmful bacterial disease in citrus production in the world, and has been seriously ravaging the citrus groves of South China since the 1930s. The surveillance of the epidemiological characteristics of HLB is of utmost priority for citrus production in this region. In order to explore the effects of disease control measures, analyses on the space–time statistical features of the HLB epidemic, from 2019 to 2021, within six orchards in the Guangdong province are presented. Overall, the number of citrus plants in the orchards usually slightly decreased year by year. The reduction was mainly related to the level of plant susceptibility, which is correlated with citrus varieties. The maximum disease severity (incidence and race increment) was correlated with the awareness of this disease and the management intensity applied by the manager. A higher disease index was found in the conventional management orchards than in the comprehensive prevention and control orchards. Proper insect-protective screen houses can effectively prevent the epidemic of HLB, without affecting the fruit quality, and can also aid with higher yields. A high correlation was found between the geometry and topography of orchards and the HLB epidemic due to the wind direction from May to September and the Asia citrus psyllid activity characteristics. For flat orchards, the incidence of HLB in the north and entrance areas was higher than that in the southwest. In the mountain area, the incidence of the windward side in the south was higher than that of the leeward side in the north. Diseased trees tended to have an edge effect in the grove, whereas the trees of the same disease scale were found clustered in their distribution. These results allow a better understanding of HLB epidemiology and provide guidance for the early warning of HLB in new groves in areas that are severely affected by this disease. Furthermore, they also provide a scientific basis for the comprehensive prevention and control of HLB in old groves.
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11
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Ribeiro C, Xu J, Hendrich C, Pandey SS, Yu Q, Gmitter FG, Wang N. Seasonal Transcriptome Profiling of Susceptible and Tolerant Citrus Cultivars to Citrus Huanglongbing. PHYTOPATHOLOGY 2023; 113:286-298. [PMID: 36001783 DOI: 10.1094/phyto-05-22-0179-r] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Citrus huanglongbing (HLB) caused by 'Candidatus Liberibacter asiaticus' (CLas) is the most devastating citrus disease worldwide. Most commercial citrus cultivars are susceptible to HLB, with a few more tolerant exceptions such as 'LB8-9' Sugar Belle mandarin. Transcriptomic analyses have been widely used to investigate the potential mechanisms for disease susceptibility, resistance, or tolerance. Previous transcriptomic studies related to HLB mostly focused on single time point data collection. We hypothesize that changes in day length and temperature throughout the seasons have profound effects on citrus-CLas interactions. Here, we conducted RNA-seq analyses on HLB-susceptible Valencia sweet orange and HLB-tolerant mandarin 'LB8-9' in winter, spring, summer, and fall. Significant variations in differentially expressed genes (DEGs) related to HLB were observed among the four seasons. For both cultivars, the highest number of DEGs were found in the spring. CLas infection stimulates the expression of immune-related genes such as NBS-LRR, RLK, RLCK, CDPK, MAPK pathway, reactive oxygen species (ROS), and PR genes in both cultivars, consistent with the model that HLB is a pathogen-triggered immune disease. HLB-positive mandarin 'LB8-9' trees contained higher concentrations of maltose and sucrose, which are known to scavenge ROS. In addition, mandarin 'LB8-9' showed higher expression of genes involved in phloem regeneration, which might contribute to its HLB tolerance. This study shed light on the pathogenicity mechanism of the HLB pathosystem and the tolerance mechanism against HLB, providing valuable insights into HLB management.
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Affiliation(s)
- Camila Ribeiro
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Jin Xu
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Connor Hendrich
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Sheo Shankar Pandey
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Qibin Yu
- Citrus Research & Education Center, Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Frederick G Gmitter
- Citrus Research & Education Center, Plant Molecular and Cellular Biology Program, Horticultural Sciences Department, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
| | - Nian Wang
- Citrus Research & Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences (IFAS), University of Florida, Lake Alfred, FL 33850
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12
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Levy A, Livingston T, Wang C, Achor D, Vashisth T. Canopy Density, but Not Bacterial Titers, Predicts Fruit Yield in Huanglongbing-Affected Sweet Orange Trees. PLANTS (BASEL, SWITZERLAND) 2023; 12:290. [PMID: 36679003 PMCID: PMC9863558 DOI: 10.3390/plants12020290] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 12/05/2022] [Accepted: 12/08/2022] [Indexed: 06/17/2023]
Abstract
In Florida, almost all citrus trees are affected with Huanglongbing (HLB), caused by Candidatus Liberibacter asiaticus (CLas). We characterized various parameters of HLB-affected sweet orange trees in response to yield-improving nutritional treatment, including canopy volume, canopy density and CLas Ct values, and found that the treatment improved yield and maintained canopy density for over three years, whereas untreated HLB-affected trees declined in canopy density. The nutritional treatment did not affect CLas titer or the tree canopy volume suggesting that canopy density is a better indicator of fruit yield. To further validate the importance of canopy density, we evaluated three independent orchards (different in tree age or variety) to identify the specific traits that are correlated with fruit yields. We found that canopy density and fruit detachment force (FDF), were positively correlated with fruit yields in independent trials. Canopy density accurately distinguished between mild and severe trees in three field trials. High and low producing HLB trees had the same Ct values. Ct values did not always agree with CLas number in the phloem, as visualized by transmission electron microscopy. Our work identifies canopy density as an efficient trait to predict yields of HLB-affected trees and suggests canopy health is more relevant for yields than the CLas population.
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Affiliation(s)
- Amit Levy
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA
| | - Taylor Livingston
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
| | - Chunxia Wang
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
| | - Diann Achor
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
| | - Tripti Vashisth
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
- Horticultural Sciences, University of Florida, Gainesville, FL 32611, USA
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13
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Garcia L, Molina MC, Padgett-Pagliai KA, Torres PS, Bruna RE, García Véscovi E, González CF, Gadea J, Marano MR. A serralysin-like protein of Candidatus Liberibacter asiaticus modulates components of the bacterial extracellular matrix. Front Microbiol 2022; 13:1006962. [DOI: 10.3389/fmicb.2022.1006962] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/26/2022] [Indexed: 11/13/2022] Open
Abstract
Huanglongbing (HLB), the current major threat for Citrus species, is caused by intracellular alphaproteobacteria of the genus Candidatus Liberibacter (CaL), with CaL asiaticus (CLas) being the most prevalent species. This bacterium inhabits phloem cells and is transmitted by the psyllid Diaphorina citri. A gene encoding a putative serralysin-like metalloprotease (CLIBASIA_01345) was identified in the CLas genome. The expression levels of this gene were found to be higher in citrus leaves than in psyllids, suggesting a function for this protease in adaptation to the plant environment. Here, we study the putative role of CLas-serralysin (Las1345) as virulence factor. We first assayed whether Las1345 could be secreted by two different surrogate bacteria, Rhizobium leguminosarum bv. viciae A34 (A34) and Serratia marcescens. The protein was detected only in the cellular fraction of A34 and S. marcescens expressing Las1345, and increased protease activity of those bacteria by 2.55 and 4.25-fold, respectively. In contrast, Las1345 expressed in Nicotiana benthamiana leaves did not show protease activity nor alterations in the cell membrane, suggesting that Las1345 do not function as a protease in the plant cell. Las1345 expression negatively regulated cell motility, exopolysaccharide production, and biofilm formation in Xanthomonas campestris pv. campestris (Xcc). This bacterial phenotype was correlated with reduced growth and survival on leaf surfaces as well as reduced disease symptoms in N. benthamiana and Arabidopsis. These results support a model where Las1345 could modify extracellular components to adapt bacterial shape and appendages to the phloem environment, thus contributing to virulence.
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14
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Bernardini C, Turner D, Wang C, Welker S, Achor D, Artiga YA, Turgeon R, Levy A. Candidatus Liberibacter asiaticus accumulation in the phloem inhibits callose and reactive oxygen species. PLANT PHYSIOLOGY 2022; 190:1090-1094. [PMID: 35880843 PMCID: PMC9516723 DOI: 10.1093/plphys/kiac346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 06/30/2022] [Indexed: 06/15/2023]
Abstract
CLas inhibits callose deposition in the sieve pores and the accumulation of reactive oxygen species to favor its cell-to-cell movement.
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Affiliation(s)
- Chiara Bernardini
- Citrus Research and Education Center, University of Florida, Lake Alfred, Florida 33850, USA
| | - Donielle Turner
- Citrus Research and Education Center, University of Florida, Lake Alfred, Florida 33850, USA
| | - Chunxia Wang
- Citrus Research and Education Center, University of Florida, Lake Alfred, Florida 33850, USA
| | - Stacy Welker
- Citrus Research and Education Center, University of Florida, Lake Alfred, Florida 33850, USA
| | - Diann Achor
- Citrus Research and Education Center, University of Florida, Lake Alfred, Florida 33850, USA
| | - Yosvanis Acanda Artiga
- Citrus Research and Education Center, University of Florida, Lake Alfred, Florida 33850, USA
| | - Robert Turgeon
- School of Integrative Plant Science, Plant Biology Section, Cornell University, Ithaca, New York 14853, USA
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15
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Huang Y, Zhu F, Koh J, Stanton D, Chen S, Wang N. Proteomic and bioinformatic analyses of proteins in the outer membrane and extracellular compartments and outer membrane vesicles of Candidatus Liberibacter species. Front Microbiol 2022; 13:977710. [PMID: 36225379 PMCID: PMC9548881 DOI: 10.3389/fmicb.2022.977710] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 09/02/2022] [Indexed: 11/23/2022] Open
Abstract
Citrus Huanglongbing (HLB) is the most devastating citrus disease in the world. Candidatus Liberibacter asiaticus (Las) is the prevalent HLB pathogen, which is yet to be cultivated. A recent study demonstrates that Las does not contain pathogenicity factors that are directly responsible for HLB symptoms. Instead, Las triggers systemic and chronic immune responses, representing a pathogen-triggered immune disease. Importantly, overproduction of reactive oxygen species (ROS) causes systemic cell death of phloem tissues, thus causing HLB symptoms. Because Las resides in the phloem tissues, it is expected that phloem cell might recognize outer membrane proteins, outer membrane vesicle (OMV) proteins and extracellular proteins of Las to contribute to the immune responses. Because Las has not been cultivated, we used Liberibacter crescens (Lcr) as a surrogate to identify proteins in the OM fraction, OMV proteins and extracellular proteins by liquid chromatography with tandem mass spectrometry (LC–MS/MS). We observed OMVs of Lcr under scanning electron microscope, representing the first experimental evidence that Liberibacter can deliver proteins to the extracellular compartment. In addition, we also further analyzed LC–MS/MS data using bioinformatic tools. Our study provides valuable information regarding the biology of Ca. Liberibacter species and identifies many putative proteins that may interact with host proteins in the phloem tissues.
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Affiliation(s)
- Yixiao Huang
- Department of Plant Pathology, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Fanchao Zhu
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, United States
| | - Jin Koh
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, United States
| | - Daniel Stanton
- Department of Plant Pathology, Citrus Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
| | - Sixue Chen
- Proteomics and Mass Spectrometry, Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, United States
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Lake Alfred, FL, United States
- *Correspondence: Nian Wang,
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16
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Pulici JDVS, Murata MM, Johnson EG. Early Physiological Plant Response and Systemic Effects of Huanglongbing Infection in Split-Root Plants. PHYTOPATHOLOGY 2022; 112:1833-1843. [PMID: 35345903 DOI: 10.1094/phyto-07-21-0293-fi] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Huanglongbing (HLB), caused by 'Candidatus Liberibacter asiaticus' (CLas), is a devastating disease of citrus. After initial infection, CLas quickly colonizes the root system before canopy symptoms develop. There is limited understanding of CLas movement from roots to canopy and local and systemic effects on root dynamics. Using split-root rhizoboxes and late summer below-the-split bud inoculation, effects of local infection on systemic disease development were studied. Upward bacterial movement from roots is linked to seasonal flushes and CLas population in roots. CLas stayed isolated to one side of the roots for at least 8 months, until the spring flush. HLB caused differential root responses depending on tree age at infection. Systemic effects, independent of CLas movement, occur very early after infection. Stimulation of root growth occurred on noninfected roots prior to CLas detection in 1.5-year-old trees but decreased in 2.5-year-old trees. Independent of tree age, root growth was stimulated during spring root flushes after CLas population stabilized. Root dieback began simultaneously with detection of CLas in roots (6 weeks postinoculation). Infection and tree age altered root lifespan. In total, 1.5-year-old CLas-infected roots from summer and fall flushes had 3 and 6 weeks reduced lifespan. In contrast, 2.5-year-old CLas-infected plants lifespan was unaffected. Season affected root lifespan with late summer root flush lifespan was three times shorter than fall or spring root flushes. Split-root inoculation allowed study of local and systemic effects of CLas infection in roots, information crucial to prolonging the productivity of HLB-affected trees.
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Affiliation(s)
| | - Mayara M Murata
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850
| | - Evan G Johnson
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850
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17
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Abstract
Although the phloem is a highly specialized tissue, certain pathogens, including phytoplasmas, spiroplasmas, and viruses, have evolved to access and live in this sequestered and protected environment, causing substantial economic harm. In particular, Candidatus Liberibacter spp. are devastating citrus in many parts of the world. Given that most phloem pathogens are vectored, they are not exposed to applied chemicals and are therefore difficult to control. Furthermore, pathogens use the phloem network to escape mounted defenses. Our review summarizes the current knowledge of phloem anatomy, physiology, and biochemistry relevant to phloem/pathogen interactions. We focus on aspects of anatomy specific to pathogen movement, including sieve plate structure and phloem-specific proteins. Phloem sampling techniques are discussed. Finally, pathogens that cause particular harm to the phloem of crop species are considered in detail.
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Affiliation(s)
- Jennifer D Lewis
- Plant Gene Expression Center, USDA-ARS, Albany, California, USA
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, California, USA
| | - Michael Knoblauch
- School of Biological Sciences, Washington State University, Pullman, Washington, USA
| | - Robert Turgeon
- Plant Biology Section, School of Integrative Plant Science, Cornell University, Ithaca, New York, USA;
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18
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Chen Q, Min A, Luo S, He J, Wu R, Lin X, Wang Y, He W, Zhang Y, Lin Y, Li M, Zhang Y, Luo Y, Tang H, Wang X. Metabolomic Analysis Revealed Distinct Physiological Responses of Leaves and Roots to Huanglongbing in a Citrus Rootstock. Int J Mol Sci 2022; 23:ijms23169242. [PMID: 36012507 PMCID: PMC9409271 DOI: 10.3390/ijms23169242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 08/14/2022] [Accepted: 08/15/2022] [Indexed: 12/11/2022] Open
Abstract
Huanglongbing (HLB) is an obstinate disease in the citrus industry. No resistant citrus resources were currently available, but various degrees of Huanglongbing tolerance exist in different germplasm. Citrus junos is emerging as one of the popular rootstocks widely used in the citrus production. However, its responses to the HLB causal agent, Candidatus Liberibacter asiaticus (CLas), were still elusive. In the current study, we investigated the physiological, anatomical, and metabolomic responses of a C. junos rootstock ‘Pujiang Xiangcheng’ by a controlled CLas grafting inoculation. The summer flushes and roots were impaired at 15 weeks after inoculation, although typical leaf symptomatic phenotypes were not obvious. The chlorophyll pigments and the photosynthetic rate were compromised. The phloem sieve tubes were still working, despite the fact that the callose was deposited and the starch granules were accumulated in the phloem cells. A wide, targeted metabolomic analysis was carried out to explore the systematic alterations of the metabolites at this early stage of infection in the leaves and root system. The differentially accumulated metabolites in the CLas-affected leaves and roots compared with the mock-inoculation control tissues revealed that distinct responses were obvious. Besides the commonly observed alteration of sugar and amino acids, the active break down of starch in the roots was discovered. The different types of fatty acids were altered in the two tissues, with a more pronounced content decline in the roots. Our results not only provided fundamental knowledge about the response of the C. junos rootstock to the HLB disease, but also presented new insights into the host–pathogen interaction in the early stages.
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Affiliation(s)
- Qing Chen
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Ailing Min
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Shu Luo
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Jinwei He
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Runqin Wu
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Ximeng Lin
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Yan Wang
- Institute of Pomology and Olericulture, Sichuan Agricultural Universtiy, Chengdu 611130, China
| | - Wen He
- Institute of Pomology and Olericulture, Sichuan Agricultural Universtiy, Chengdu 611130, China
| | - Yunting Zhang
- Institute of Pomology and Olericulture, Sichuan Agricultural Universtiy, Chengdu 611130, China
| | - Yuanxiu Lin
- Institute of Pomology and Olericulture, Sichuan Agricultural Universtiy, Chengdu 611130, China
| | - Mengyao Li
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Yong Zhang
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Ya Luo
- College of Horticulture, Sichuan Agricultural University, Chengdu 611130, China
| | - Haoru Tang
- Institute of Pomology and Olericulture, Sichuan Agricultural Universtiy, Chengdu 611130, China
- Correspondence: (H.T.); (X.W.)
| | - Xiaorong Wang
- Institute of Pomology and Olericulture, Sichuan Agricultural Universtiy, Chengdu 611130, China
- Correspondence: (H.T.); (X.W.)
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19
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Keeley M, Rowland D, Vincent C. Citrus photosynthesis and morphology acclimate to phloem-affecting huanglongbing disease at the leaf and shoot levels. PHYSIOLOGIA PLANTARUM 2022; 174:e13662. [PMID: 35253914 DOI: 10.1111/ppl.13662] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2021] [Revised: 03/02/2022] [Accepted: 03/03/2022] [Indexed: 06/14/2023]
Abstract
Huanglongbing (HLB) is a phloem-affecting disease in citrus that reduces growth and impacts global citrus production. HLB is caused by a phloem-limited bacterium (Candidatus Liberibacter asiaticus). By inhibiting phloem function, HLB stunts sink growth, including the production of new shoots and leaves, and induces hyperaccumulation of foliar starch. HLB induces feedback inhibition of photosynthesis by reducing foliar carbohydrate export. Here, we assessed the relationship of bacterial distribution within the foliage, foliar starch accumulation, and net CO2 assimilation (Anet ). Because HLB impacts canopy morphology, we developed a chamber to measure whole-shoot Anet to test the effects of HLB at both the leaf and shoot level. Whole-shoot level Anet saturated at high irradiance, and green stems had high photosynthetic rates compared to leaves. Starch accumulation was correlated with bacterial population, and starch was negatively correlated with Anet at the leaf but not at the shoot level. Starch increased initially after infection, then decreased progressively with increasing length of infection. HLB infection reduced Anet at the leaf level but increased it at the whole-shoot level, in association with reduced leaf size and greater relative contribution of stems to the photosynthetic surface area. Although HLB-increased photosynthetic efficiency, total carbon fixed per shoot decreased because photosynthetic surface area was reduced. We conclude that the localized effects of infection on photosynthesis are mitigated by whole-shoot morphological acclimation over time. Stems contribute important proportions of whole-shoot Anet , and these contributions are likely increased by the morphological acclimation induced by HLB.
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Affiliation(s)
- Mark Keeley
- Agronomy Department, University of Florida, Gainesville, Florida, USA
| | - Diane Rowland
- Agronomy Department, University of Florida, Gainesville, Florida, USA
| | - Christopher Vincent
- Horticultural Sciences Department, Citrus Research and Education Center, University of Florida, Lake Alfred, Florida, USA
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20
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Padgett-Pagliai KA, Pagliai FA, da Silva DR, Gardner CL, Lorca GL, Gonzalez CF. Osmotic stress induces long-term biofilm survival in Liberibacter crescens. BMC Microbiol 2022; 22:52. [PMID: 35148684 PMCID: PMC8832773 DOI: 10.1186/s12866-022-02453-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 01/21/2022] [Indexed: 11/24/2022] Open
Abstract
Citrus greening, also known as Huanglongbing (HLB), is a devastating citrus plant disease caused predominantly by Liberibacter asiaticus. While nearly all Liberibacter species remain uncultured, here we used the culturable L. crescens BT-1 as a model to examine physiological changes in response to the variable osmotic conditions and nutrient availability encountered within the citrus host. Similarly, physiological responses to changes in growth temperature and dimethyl sulfoxide concentrations were also examined, due to their use in many of the currently employed therapies to control the spread of HLB. Sublethal heat stress was found to induce the expression of genes related to tryptophan biosynthesis, while repressing the expression of ribosomal proteins. Osmotic stress induces expression of transcriptional regulators involved in expression of extracellular structures, while repressing the biosynthesis of fatty acids and aromatic amino acids. The effects of osmotic stress were further evaluated by quantifying biofilm formation of L. crescens in presence of increasing sucrose concentrations at different stages of biofilm formation, where sucrose-induced osmotic stress delayed initial cell attachment while enhancing long-term biofilm viability. Our findings revealed that exposure to osmotic stress is a significant contributing factor to the long term survival of L. crescens and, possibly, to the pathogenicity of other Liberibacter species.
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Affiliation(s)
- Kaylie A Padgett-Pagliai
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Sciences, University of Florida, 2033 Mowry Road, PO Box 103610, Gainesville, FL, 32610-3610, USA
| | - Fernando A Pagliai
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Sciences, University of Florida, 2033 Mowry Road, PO Box 103610, Gainesville, FL, 32610-3610, USA
| | - Danilo R da Silva
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Sciences, University of Florida, 2033 Mowry Road, PO Box 103610, Gainesville, FL, 32610-3610, USA
| | - Christopher L Gardner
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Sciences, University of Florida, 2033 Mowry Road, PO Box 103610, Gainesville, FL, 32610-3610, USA
| | - Graciela L Lorca
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Sciences, University of Florida, 2033 Mowry Road, PO Box 103610, Gainesville, FL, 32610-3610, USA
| | - Claudio F Gonzalez
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Sciences, University of Florida, 2033 Mowry Road, PO Box 103610, Gainesville, FL, 32610-3610, USA.
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21
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Welker S, Pierre M, Santiago JP, Dutt M, Vincent C, Levy A. Phloem transport limitation in Huanglongbing-affected sweet orange is dependent on phloem-limited bacteria and callose. TREE PHYSIOLOGY 2022; 42:379-390. [PMID: 34617106 DOI: 10.1093/treephys/tpab134] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 10/01/2021] [Indexed: 05/11/2023]
Abstract
Huanglongbing (HLB), caused by Candidatus `Liberibacter asiaticus' (CLas), is a phloem-limited disease that disrupts citrus production in affected areas. In HLB-affected plants, phloem sieve plate pores accumulate callose, and leaf carbohydrate export is reduced. However, whether HLB causes a reduction in carbohydrate phloem translocation speed and the quantitative relationships among callose, CLas population and phloem translocation are still unknown. In this work, a procedure was developed to concurrently measure sugar transport, callose deposition and relative pathogen population at different locations throughout the stem. Increasing quantities of CLas genetic material were positively correlated with quantity and density of callose deposits and negatively correlated with phloem translocation speed. Callose deposit quantity was position and rootstock dependent and was negatively correlated with phloem translocation speed, suggesting a localized relationship. Remarkably, callose accumulation and phloem translocation disruption in the scion were dependent on rootstock genotype. Regression results suggested that the interaction of Ct values and number of phloem callose depositions, but not their size or density, explained the effects on translocation speed. Sucrose, starch and sink 14C label allocation data support the interpretation of a transport pathway limitation by CLas infection. This work shows that the interaction of local accumulation of callose and CLas affects phloem transport. Furthermore, the extent of this accumulation is attenuated by the rootstock and provides important information about the disease mechanism of phloem-inhabiting bacteria. Together, these results constitute the first example of a demonstrated transport limitation of phloem function by a microbial infection.
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Affiliation(s)
- Stacy Welker
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA
| | - Myrtho Pierre
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
| | - James P Santiago
- Plant Resilience Institute and MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
| | - Manjul Dutt
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
- Department of Horticulture, University of Florida, Gainesville, FL 32611, USA
| | - Christopher Vincent
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
- Department of Horticulture, University of Florida, Gainesville, FL 32611, USA
| | - Amit Levy
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA
- Department of Plant Pathology, University of Florida, Gainesville, FL 32611, USA
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22
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Ribeiro C, Stitt M, Hotta CT. How Stress Affects Your Budget-Stress Impacts on Starch Metabolism. FRONTIERS IN PLANT SCIENCE 2022; 13:774060. [PMID: 35222460 PMCID: PMC8874198 DOI: 10.3389/fpls.2022.774060] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 01/12/2022] [Indexed: 05/16/2023]
Abstract
Starch is a polysaccharide that is stored to be used in different timescales. Transitory starch is used during nighttime when photosynthesis is unavailable. Long-term starch is stored to support vegetative or reproductive growth, reproduction, or stress responses. Starch is not just a reserve of energy for most plants but also has many other roles, such as promoting rapid stomatal opening, making osmoprotectants, cryoprotectants, scavengers of free radicals and signals, and reverting embolised vessels. Biotic and abiotic stress vary according to their nature, strength, duration, developmental stage of the plant, time of the day, and how gradually they develop. The impact of stress on starch metabolism depends on many factors: how the stress impacts the rate of photosynthesis, the affected organs, how the stress impacts carbon allocation, and the energy requirements involved in response to stress. Under abiotic stresses, starch degradation is usually activated, but starch accumulation may also be observed when growth is inhibited more than photosynthesis. Under biotic stresses, starch is usually accumulated, but the molecular mechanisms involved are largely unknown. In this mini-review, we explore what has been learned about starch metabolism and plant stress responses and discuss the current obstacles to fully understanding their interactions.
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Affiliation(s)
| | - Mark Stitt
- Max Planck Institute for Molecular Plant Physiology, Potsdam, Germany
| | - Carlos Takeshi Hotta
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil
- *Correspondence: Carlos Takeshi Hotta,
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23
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Sivager G, Calvez L, Bruyere S, Boisne-Noc R, Hufnagel B, Cebrian-Torrejon G, Doménech-Carbó A, Gros O, Ollitrault P, Morillon R. Better tolerance to Huanglongbing is conferred by tetraploid Swingle citrumelo rootstock and is influenced by the ploidy of the scion. FRONTIERS IN PLANT SCIENCE 2022; 13:1030862. [PMID: 36407590 PMCID: PMC9669798 DOI: 10.3389/fpls.2022.1030862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2022] [Accepted: 10/12/2022] [Indexed: 05/14/2023]
Abstract
Huanglongbing (HLB) is a disease that is responsible for the death of millions of trees worldwide. The bacterial causal agent belongs to Candidatus Liberibacter spp., which is transmitted by psyllids. The bacterium lead most of the time to a reaction of the tree associated with callose synthesis at the phloem sieve plate. Thus, the obstruction of pores providing connections between adjacent sieve elements will limit the symplastic transport of the sugars and starches synthesized through photosynthesis. In the present article, we investigated the impact of the use of tetraploid Swingle citrumelo (Citrus paradisi Macfrad × Poncirus trifoliata [L.] Raf) rootstock on HLB tolerance, compared to its respective diploid. HLB-infected diploid and tetraploid rootstocks were investigated when grafted with Mexican and Persian limes. Secondary roots were anatomically studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to observe callose deposition at the phloem sieve plate and to evaluate the impact of the bacterium's presence at the cellular level. Voltammetry of immobilized microparticles (VIMP) in roots was applied to determine the oxidative stress status of root samples. In the field, Mexican and Persian lime leaves of trees grafted onto tetraploid rootstock presented less symptoms of HLB. Anatomical analysis showed much stronger secondary root degradation in diploid rootstock, compared to tetraploid rootstock. Analysis of the root sieve plate in control root samples showed that pores were approximately 1.8-fold larger in tetraploid Swingle citrumelo than in its respective diploid. SEM analyses of root samples did not reveal any callose deposition into pores of diploid and tetraploid genotypes. VIMP showed limited oxidative stress in tetraploid samples, compared to diploid ones. These results were even strongly enhanced when rootstocks were grafted with Persian limes, compared to Mexican limes, which was corroborated by stronger polyphenol contents. TEM analysis showed that the bacteria was present in both ploidy root samples with no major impacts detected on cell walls or cell structures. These results reveal that tetraploid Swingle citrumelo rootstock confers better tolerance to HLB than diploid. Additionally, an even stronger tolerance is achieved when the triploid Persian lime scion is associated.
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Affiliation(s)
- Gary Sivager
- Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Equipe Structure Evolutive des Agrumes, Polyploïdie et Amélioration Génétique (SEAPAG), F-97170 Petit-Bourg, Guadeloupe, French West Indies—Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Univ. Montpellier, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Institut Agro, Montpellier, France
| | - Leny Calvez
- Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Equipe Structure Evolutive des Agrumes, Polyploïdie et Amélioration Génétique (SEAPAG), F-97170 Petit-Bourg, Guadeloupe, French West Indies—Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Univ. Montpellier, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Institut Agro, Montpellier, France
| | - Saturnin Bruyere
- Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Equipe Structure Evolutive des Agrumes, Polyploïdie et Amélioration Génétique (SEAPAG), F-97170 Petit-Bourg, Guadeloupe, French West Indies—Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Univ. Montpellier, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Institut Agro, Montpellier, France
| | - Rosiane Boisne-Noc
- Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Equipe Structure Evolutive des Agrumes, Polyploïdie et Amélioration Génétique (SEAPAG), F-97170 Petit-Bourg, Guadeloupe, French West Indies—Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Univ. Montpellier, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Institut Agro, Montpellier, France
| | - Barbara Hufnagel
- Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Equipe Structure Evolutive des Agrumes, Polyploïdie et Amélioration Génétique (SEAPAG), F-97170 Petit-Bourg, Guadeloupe, French West Indies—Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Univ. Montpellier, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Institut Agro, Montpellier, France
| | - Gerardo Cebrian-Torrejon
- Connaissance et Valorisation: Chimie des Matériaux, Environnement, Energie (COVACHIM-M2E) Laboratory Equipe Associée (EA) 3592, Unité de Formations et de Recherche (UFR) des Sciences Exactes et Naturelles, Université des Antilles, Pointe-à-Pitre, Guadeloupe
| | - Antonio Doménech-Carbó
- Departament de Química Ananlítica, Facultat de Química, Universitat de València, Valencia, Spain
| | - Olivier Gros
- Centre commun de caractérisation des matériaux des Antilles et de la Guyane (C3MAG), Unité de Formations et de Recherche (UFR) des Sciences Exactes et Naturelles, Université des Antilles, Pointe-à-Pitre, Guadeloupe
- Institut de Systématique, Evolution, Biodiversité, Muséum National d’Histoire Naturelle, Centre National de la Recherche Scientifique (CNRS), Sorbonne Université, École Pratique des Hautes Etudes (EPHE), Université des Antilles, Campus de Fouillole, Pointe-à-Pitre, France
| | - Patrick Ollitrault
- Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Equipe Structure Evolutive des Agrumes, Polyploïdie et Amélioration Génétique (SEAPAG), F-97170 Petit-Bourg, Guadeloupe, French West Indies—Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Univ. Montpellier, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Institut Agro, Montpellier, France
| | - Raphaël Morillon
- Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Equipe Structure Evolutive des Agrumes, Polyploïdie et Amélioration Génétique (SEAPAG), F-97170 Petit-Bourg, Guadeloupe, French West Indies—Unité Mixte de Recherche Amélioration Génétique et Adaptation des Plantes méditerranéennes et tropicales (UMR AGAP) Institut, Univ. Montpellier, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement (INRAE), Institut Agro, Montpellier, France
- *Correspondence: Raphaël Morillon,
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24
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Merfa MV, Naranjo E, Shantharaj D, De La Fuente L. Growth of ' Candidatus Liberibacter asiaticus' in Commercial Grapefruit Juice-Based Media Formulations Reveals Common Cell Density-Dependent Transient Behaviors. PHYTOPATHOLOGY 2022; 112:131-144. [PMID: 34340531 DOI: 10.1094/phyto-06-21-0228-fi] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The phloem-restricted, insect-transmitted bacterium 'Candidatus Liberibacter asiaticus' (CLas) is associated with huanglongbing (HLB), the most devastating disease of citrus worldwide. The inability to culture CLas impairs the understanding of its virulence mechanisms and the development of effective management strategies to control this incurable disease. Previously, our research group used commercial grapefruit juice (GJ) to prolong the viability of CLas in vitro. In the present study, GJ was amended with a wide range of compounds and incubated under different conditions to optimize CLas growth. Remarkably, results showed that CLas growth ratios were inversely proportional to the initial inoculum concentration. This correlation is probably regulated by a cell density-dependent mechanism, because diluting samples between subcultures allowed CLas to resume growth. Moreover, strategies to reduce the cell density of CLas, such as subculturing at short intervals and incubating samples under flow conditions, allowed this bacterium to multiply and reach maximum growth as early as 3 days after inoculation, although no sustained exponential growth was observed under any tested condition. Unfortunately, cultures were only transient, because CLas lost viability over time; nevertheless, we obtained populations of about 105 genome equivalents/ml repeatedly. Finally, we established an ex vivo system to grow CLas within periwinkle calli that could be used to propagate bacterial inoculum in the lab. In this study we determined the influence of a comprehensive set of conditions and compounds on CLas growth in culture. We hope our results will help guide future efforts toward the long-sought goal of culturing CLas axenically.
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Affiliation(s)
- Marcus V Merfa
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849
| | - Eber Naranjo
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849
| | - Deepak Shantharaj
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849
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25
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Pandey SS, Hendrich C, Andrade MO, Wang N. Candidatus Liberibacter: From Movement, Host Responses, to Symptom Development of Citrus Huanglongbing. PHYTOPATHOLOGY 2022; 112:55-68. [PMID: 34609203 DOI: 10.1094/phyto-08-21-0354-fi] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Candidatus Liberibacter spp. are fastidious α-proteobacteria that cause multiple diseases on plant hosts of economic importance, including the most devastating citrus disease: Huanglongbing (HLB). HLB was reported in Asia a century ago but has since spread worldwide. Understanding the pathogenesis of Candidatus Liberibacter spp. remains challenging as they are yet to be cultured in artificial media and infect the phloem, a sophisticated environment that is difficult to manipulate. Despite those challenges, tremendous progress has been made on Ca. Liberibacter pathosystems. Here, we first reviewed recent studies on genetic information of flagellar and type IV pili biosynthesis, their expression profiles, and movement of Ca. Liberibacter spp. inside the plant and insect hosts. Next, we reviewed the transcriptomic, proteomic, and metabolomic studies of susceptible and tolerant plant genotypes to Ca. Liberibacter spp. infection and how Ca. Liberibacter spp. adapt in plants. Analyses of the interactions between plants and Ca. Liberibacter spp. imply the involvement of immune response in the Ca. Liberibacter pathosystems. Lastly, we reviewed how Ca. Liberibacter spp. movement inside and interactions with plants lead to symptom development.
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Affiliation(s)
- Sheo Shankar Pandey
- Citrus Research and Education Center, Department of Microbiology and Cell Sciences, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Connor Hendrich
- Citrus Research and Education Center, Department of Microbiology and Cell Sciences, University of Florida, Lake Alfred, FL 33850, U.S.A
| | - Maxuel O Andrade
- Brazilian Biorenewables National Laboratory (LNBR), Brazilian Centre for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil
| | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Sciences, University of Florida, Lake Alfred, FL 33850, U.S.A
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26
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Cai L, Jain M, Sena-Vélez M, Jones KM, Fleites LA, Heck M, Gabriel DW. Tad pilus-mediated twitching motility is essential for DNA uptake and survival of Liberibacters. PLoS One 2021; 16:e0258583. [PMID: 34644346 PMCID: PMC8513845 DOI: 10.1371/journal.pone.0258583] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Accepted: 10/01/2021] [Indexed: 12/12/2022] Open
Abstract
Axenically cultured Liberibacter crescens (Lcr) is a closely related surrogate for uncultured plant pathogenic species of the genus Liberibacter, including ‘Candidatus L. asiaticus’ (CLas) and ‘Ca. L. solanacearum’ (CLso). All Liberibacters encode a completely conserved gene repertoire for both flagella and Tad (Tight Adherence) pili and all are missing genes critical for nucleotide biosynthesis. Both flagellar swimming and Tad pilus-mediated twitching motility in Lcr were demonstrated for the first time. A role for Tad pili in the uptake of extracellular dsDNA for food in Liberibacters was suspected because both twitching and DNA uptake are impossible without repetitive pilus extension and retraction, and no genes encoding other pilus assemblages or mechanisms for DNA uptake were predicted to be even partially present in any of the 35 fully sequenced Liberibacter genomes. Insertional mutations of the Lcr Tad pilus genes cpaA, cpaB, cpaE, cpaF and tadC all displayed such severely reduced growth and viability that none could be complemented. A mutation affecting cpaF (motor ATPase) was further characterized and the strain displayed concomitant loss of twitching, viability and reduced periplasmic uptake of extracellular dsDNA. Mutations of comEC, encoding the inner membrane competence channel, had no effect on either motility or growth but completely abolished natural transformation in Lcr. The comEC mutation was restored by complementation using comEC from Lcr but not from CLas strain psy62 or CLso strain RS100, indicating that unlike Lcr, these pathogens were not naturally competent for transformation. This report provides the first evidence that the Liberibacter Tad pili are dynamic and essential for both motility and DNA uptake, thus extending their role beyond surface adherence.
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Affiliation(s)
- Lulu Cai
- Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America
| | - Mukesh Jain
- Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America
| | - Marta Sena-Vélez
- Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America
| | - Kathryn M. Jones
- Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America
| | - Laura A. Fleites
- USDA Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, New York, United States of America
| | - Michelle Heck
- USDA Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, New York, United States of America
| | - Dean W. Gabriel
- Plant Pathology Department, University of Florida, Gainesville, Florida, United States of America
- * E-mail:
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27
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Raiol-Junior LL, Cifuentes-Arenas JC, Cunniffe NJ, Turgeon R, Lopes SA. Modeling ' Candidatus Liberibacter asiaticus' Movement Within Citrus Plants. PHYTOPATHOLOGY 2021; 111:1711-1719. [PMID: 33724870 DOI: 10.1094/phyto-12-20-0559-r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The phloem-limited 'Candidatus Liberibacter asiaticus' (Las) causes huanglongbing, a destructive citrus disease. Graft-inoculated potted plants were used to assess Las speed of movement in phloem in the greenhouse, and the impacts of temperature on plant colonization in growth-chamber experiments. For assessment of Las speed, plants were inoculated at the main stem and assessed over time by quantitative PCR (qPCR) or symptoms at various distances from the inoculum. For colonization, the plants were inoculated in one of two opposite top branches, maintained at from 8 to 20°C, from 18 to 30°C, or from 24 to 38°C daily range, and assessed by qPCR of samples taken from noninoculated shoots. For all experiments, frequencies of Las-positive sites were submitted to analysis of variance and binomial generalized linear model and logistic regression analyses. Probabilities of detecting Las in greenhouse plants were functions of time and distance from the inoculation site, which resulted in 2.9 and 3.8 cm day-1 average speed of movement. In growth chambers, the temperature impacted plant colonization by Las, new shoot emission, and symptom expression. After a 7-month exposure time, Las was absent in all new shoots in the cooler environment (average three per plant), and present in 70% at the milder environment (six shoots, severe symptoms) and 25% in the warmer environment (eight shoots, no visible symptoms). Temperature of 25.7°C was the optimum condition for plant colonization. This explains the higher impact and incidence of huanglongbing disease during the winter months or regions of milder climates in Brazil.
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Affiliation(s)
- Laudecir L Raiol-Junior
- Unversidade Estadual Paulista "Júlio de Mesquita Filho," 14884-900 Jaboticabal, São Paulo, Brazil
| | - Juan C Cifuentes-Arenas
- Unversidade Estadual Paulista "Júlio de Mesquita Filho," 14884-900 Jaboticabal, São Paulo, Brazil
- Fundo de Defesa da Citricultura, 14807-040 Araraquara, São Paulo, Brazil
| | - Nik J Cunniffe
- Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, U.K
| | - Robert Turgeon
- Department of Plant Biology, Cornell University, Ithaca, NY 14853, U.S.A
| | - Silvio A Lopes
- Fundo de Defesa da Citricultura, 14807-040 Araraquara, São Paulo, Brazil
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28
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Wu B, Li N, Deng Z, Luo F, Duan Y. Selection and Evaluation of a Thornless and HLB-Tolerant Bud-Sport of Pummelo Citrus With an Emphasis on Molecular Mechanisms. FRONTIERS IN PLANT SCIENCE 2021; 12:739108. [PMID: 34531892 PMCID: PMC8438139 DOI: 10.3389/fpls.2021.739108] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Accepted: 08/04/2021] [Indexed: 06/01/2023]
Abstract
The selection of elite bud-sports is an important breeding approach in horticulture. We discovered and evaluated a thornless pummelo bud-sport (TL) that grew more vigorously and was more tolerant to Huanglongbing (HLB) than the thorny wild type (W). To reveal the underlying molecular mechanisms, we carried out whole-genome sequencing of W, and transcriptome comparisons of W, TL, and partially recovered thorny "mutants" (T). The results showed W, TL, and T varied in gene expression, allelic expression, and alternative splicing. Most genes/pathways with significantly altered expression in TL compared to W remained similarly altered in T. Pathway and gene ontology enrichment analysis revealed that the expression of multiple pathways, including photosynthesis and cell wall biosynthesis, was altered among the three genotypes. Remarkably, two polar auxin transporter genes, PIN7 and LAX3, were expressed at a significantly lower level in TL than in both W and T, implying alternation of polar auxin transport in TL may be responsible for the vigorous growth and thornless phenotype. Furthermore, 131 and 68 plant defense-related genes were significantly upregulated and downregulated, respectively, in TL and T compared with W. These genes may be involved in enhanced salicylic acid (SA) dependent defense and repression of defense inducing callose deposition and programmed cell death. Overall, these results indicated that the phenotype changes of the TL bud-sport were associated with tremendous transcriptome alterations, providing new clues and targets for breeding and gene editing for citrus improvement.
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Affiliation(s)
- Bo Wu
- School of Computing, Clemson University, Clemson, SC, United States
| | - Na Li
- United States Department of Agriculture-Agriculture Research Service-United States Horticultural Research Laboratory, Fort Pierce, FL, United States
- College of Horticulture, Hunan Agricultural University, Changsha, China
| | - Zhanao Deng
- Department of Environmental Horticulture, Gulf Coast Research and Education Center, IFAS, University of Florida, Wimauma, FL, United States
| | - Feng Luo
- School of Computing, Clemson University, Clemson, SC, United States
| | - Yongping Duan
- United States Department of Agriculture-Agriculture Research Service-United States Horticultural Research Laboratory, Fort Pierce, FL, United States
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29
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Merli ML, Padgett-Pagliai KA, Cuaycal AE, Garcia L, Marano MR, Lorca GL, Gonzalez CF. ' Candidatus Liberibacter asiaticus' Multimeric LotP Mediates Citrus sinensis Defense Response Activation. Front Microbiol 2021; 12:661547. [PMID: 34421834 PMCID: PMC8371691 DOI: 10.3389/fmicb.2021.661547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 07/06/2021] [Indexed: 11/13/2022] Open
Abstract
‘Candidatus Liberibacter asiaticus’ is known as the most pathogenic organism associated with citrus greening disease. Since its publicized emergence in Florida in 2005, ‘Ca. L. asiaticus’ remains unculturable. Currently, a limited number of potential disease effectors have been identified through in silico analysis. Therefore, these potential effectors remain poorly characterized and do not fully explain the complexity of symptoms observed in citrus trees infected with ‘Ca. L. asiaticus.’ LotP has been identified as a potential effector and have been partially characterized. This protein retains structural homology to the substrate binding domain of the Lon protease. LotP interacts with chaperones like GroEL, Hsp40, DnaJ, and ClpX and may exercise its biological role through interactions with different proteins involved in proteostasis networks. Here, we evaluate the interactome of LotP—revealing a new protein–protein interaction target (Lon-serine protease) and its effect on citrus plant tissue integrity. We found that via protein–protein interactions, LotP can enhance Lon protease activity, increasing the degradation rate of its specific targets. Infiltration of purified LotP strained citrus plant tissue causing photoinhibition and chlorosis after several days. Proteomics analysis of LotP tissues recovering after the infiltration revealed a large abundance of plant proteins associated with the stabilization and processing of mRNA transcripts, a subset of important transcription factors; and pathways associated with innate plant defense were highly expressed. Furthermore, interactions and substrate binding module of LotP suggest potential interactions with plant proteins, most likely proteases.
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Affiliation(s)
- Marcelo L Merli
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
| | - Kaylie A Padgett-Pagliai
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
| | - Alexandra E Cuaycal
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
| | - Lucila Garcia
- Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Tecnológicas, Rosario, Argentina
| | - Maria Rosa Marano
- Instituto de Biología Molecular y Celular de Rosario (IBR), Consejo Nacional de Investigaciones Científicas y Tecnológicas, Rosario, Argentina
| | - Graciela L Lorca
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
| | - Claudio F Gonzalez
- Department of Microbiology and Cell Science, Genetics Institute, Institute of Food and Agricultural Science, University of Florida, Gainesville, FL, United States
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30
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Munir S, Ahmed A, Li Y, He P, Singh BK, He P, Li X, Asad S, Wu Y, He Y. The hidden treasures of citrus: finding Huanglongbing cure where it was lost. Crit Rev Biotechnol 2021; 42:634-649. [PMID: 34325576 DOI: 10.1080/07388551.2021.1942780] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Huanglongbing (HLB), a deadly citrus disease which has significantly downsized the entire industry worldwide. The intractable and incurable disease has brought the citriculture an enormous loss of productivity. With no resistant varieties available, failure of chemical treatments despite repeated applications, and hazardous consequences to environmental health, have led to large-scale research to find a sustainable cure. Inside plants, the key determinants of health and safety, live the endophytic microbes. Endophytes possess unrivaled plant benefiting properties. The progression of HLB is known to cause disturbance in endophytic bacterial communities. Given the importance of the plant endophytic microbiome in disease progression, the notion of engineering microbiomes through indigenous endophytes is attracting scientific attention which is considered revolutionary as it precludes the incompatibility concerns associated with the use of alien (microbes from other plant species) endophytes. In this review, we briefly discuss the transformation of the plant-pathogen-environment to the plant-pathogen-microbial system in a disease triangle. We also argue the employment of indigenous endophytes isolated from a healthy state to engineer the diseased citrus endophytic microbiomes that can provide sustainable solution for vascular pathogens. We evaluated the plethora of microbiomes responses to the re-introduction of endophytes which leads to disease resistance in the citrus host. The idea is not merely confined to citrus-HLB, but it is globally applicable for tailoring a customized cure for general plant-pathogen systems particularly for the diseases caused by the vascular system-restricted pathogens.
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Affiliation(s)
- Shahzad Munir
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China
| | - Ayesha Ahmed
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China
| | - Yongmei Li
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China
| | - Pengbo He
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China
| | - Brajesh K Singh
- Hawkesbury Institute for the Environment, Western Sydney University, Penrith South, Australia.,Global Centre for Land Based Innovation, Western Sydney University, Penrith South, Australia
| | - Pengfei He
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China
| | - Xingyu Li
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China
| | - Suhail Asad
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China
| | - Yixin Wu
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China.,College of Agronomy and Biotechnology, Yunnan Agricultural University, Kunming, P. R. China
| | - Yueqiu He
- State Key Laboratory for Conservation and Utilization of Bio-resources in Yunnan, Yunnan Agricultural University, Kunming, P. R. China
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31
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Vasconcelos FNC, Li J, Pang Z, Vincent C, Wang N. The Total Population Size of ' Candidatus Liberibacter asiaticus' Inside the Phloem of Citrus Trees and the Corresponding Metabolic Burden Related to Huanglongbing Disease Development. PHYTOPATHOLOGY 2021; 111:1122-1128. [PMID: 33090080 DOI: 10.1094/phyto-09-20-0388-r] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
'Candidatus Liberibacter asiaticus' (CLas) is the predominant causal agent of citrus huanglongbing, the most devastating citrus disease worldwide. CLas colonizes phloem tissue and causes phloem dysfunction. The pathogen population size in local tissues and in the whole plant is critical for the development of disease symptoms by determining the load of pathogenicity factors and metabolic burden to the host. However, the total population size of CLas in a whole plant and the ratio of CLas to citrus cells in local tissues have not been addressed previously. The total CLas population size for 2.5-year-old 'Valencia' sweet orange on 'Kuharske' citrange rootstock trees was quantified using quantitative PCR to be approximately 1.74 × 109 cells/tree, whereas 7- and 20-year-old sweet orange trees were estimated to be 4.3 × 1010 cells/tree, and 6.0 × 1010 cells/tree, respectively. The majority of CLas cells were distributed in leaf tissues (55.58%), followed by those in branch (36.78%), feeder root (4.75%), trunk (2.39%), and structural root (0.51%) tissues. The ratios of citrus cells to CLas cells for branch, leaf, trunk, feeder root, and structural root samples were within approximately 39 to 79, 44 to 124, 153 to 1,355, 191 to 1,054, and 561 to 3,760, respectively, representing the metabolic burden of CLas in different organs. It was estimated that the ratios of phloem cells to CLas cells for branch, leaf, trunk, feeder root, and structural root samples are approximately 0.39 to 0.79, 0.44 to 1.24, 1.53 to 13.55, 1.91 to 10.54, and 5.61 to 37.60, respectively. Approximately 0.01% of the total citrus phloem volume was estimated to be occupied by CLas, explaining the difficulty to observe CLas in most tissues under transmission electron microscopy. The CLas titer inside the leaf was estimated to be approximately 1.64 × 106 cells/leaf or 9.2 × 104 cells cm-2 in leaves, approximately 104 times less than that of typical apoplastic bacterial pathogens. This study provides quantitative estimates of phloem colonization by bacterial pathogens and furthers the understanding of the biology and virulence mechanisms of CLas.
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Affiliation(s)
- Fernanda N C Vasconcelos
- Citrus Research and Education Center (CREC), Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850
| | - Jinuyn Li
- Citrus Research and Education Center (CREC), Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850
| | - Zhiqian Pang
- Citrus Research and Education Center (CREC), Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850
| | - Christopher Vincent
- Citrus Research and Education Center (CREC), Department of Horticultural Sciences, University of Florida, Lake Alfred, FL 33850
| | - Nian Wang
- Citrus Research and Education Center (CREC), Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850
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32
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Fang F, Guo H, Zhao A, Li T, Liao H, Deng X, Xu M, Zheng Z. A Significantly High Abundance of " Candidatus Liberibacter asiaticus" in Citrus Fruit Pith: in planta Transcriptome and Anatomical Analyses. Front Microbiol 2021; 12:681251. [PMID: 34177866 PMCID: PMC8225937 DOI: 10.3389/fmicb.2021.681251] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 05/10/2021] [Indexed: 11/20/2022] Open
Abstract
Huanglongbing, a highly destructive disease of citrus, is associated with the non-culturable phloem-limited α-proteobacterium "Candidatus Liberibacter asiaticus" (CLas). The distribution patterns of CLas in infected plant are variable and not consistent, which make the CLas detection and characterization more challenging. Here, we performed a systemic analysis of CLas distribution in citrus branches and fruits of 14 cultivars. A significantly high concentration of CLas was detected in fruit pith (dorsal vascular bundle) of 14 citrus cultivars collected at fruit maturity season. A 2-year monitoring assay of CLas population in citrus branches of "Shatangju" mandarin (Citrus reticulata Blanco "Shatangju") revealed that CLas population already exhibited a high level even before the appearance of visual symptoms in the fruit rind. Quantitative analyses of CLas in serial 1.5-cm segments of fruit piths showed the CLas was unevenly distributed within fruit pith and tended to colonize in the middle or distal (stylar end) regions of pith. The use of CLas-abundant fruit pith for dual RNA-seq generated higher-resolution CLas transcriptome data compared with the leaf samples. CLas genes involved in transport system, flagellar assembly, lipopolysaccharide biosynthesis, virulence, stress response, and cell surface structure, as well as host genes involved in biosynthesis of antimicrobial-associated secondary metabolites, was up-regulated in leaf midribs compared with fruit pith. In addition, CLas infection caused the severe collapse in phloem and callose deposition in the plasmodesmata of fruit pith. The ability of fruit pith to support multiplication of CLas to high levels makes it an ideal host tissue for morphological studies and in planta transcriptome analyses of CLas-host interactions.
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Affiliation(s)
- Fang Fang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Hengyu Guo
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Anmin Zhao
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Tao Li
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Huihong Liao
- Horticulture Research Institute, Guangxi Academy of Agricultural Sciences, Nanning, China
| | - Xiaoling Deng
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Meirong Xu
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
| | - Zheng Zheng
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, China
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33
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Alves MN, Cifuentes-Arenas JC, Raiol-Junior LL, Ferro JA, Peña L. Early Population Dynamics of " Candidatus Liberibacter asiaticus" in Susceptible and Resistant Genotypes After Inoculation With Infected Diaphorina citri Feeding on Young Shoots. Front Microbiol 2021; 12:683923. [PMID: 34177870 PMCID: PMC8219961 DOI: 10.3389/fmicb.2021.683923] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 04/29/2021] [Indexed: 11/14/2022] Open
Abstract
Huanglongbing is a highly destructive citrus disease associated with “Candidatus Liberibacter asiaticus” (Las), a phloem−limited and non-culturable bacterium, naturally transmitted by the psyllid Diaphorina citri. Although diverse approaches have been used to understand the molecular mechanisms involved in the pathogen–host interaction, such approaches have focused on already infected and/or symptomatic plants, missing early events in the initial days post-inoculation. This study aimed to identify the time course of Las multiplication and whole-plant colonization immediately following inoculation by infected psyllids feeding for 2 days. Thus, the experimental approach was to track Las titers after psyllid inoculation in new shoots (NS) of Citrus × sinensis (susceptible), Murraya paniculata (partially resistant), and Bergera koenigii (fully resistant). Soon after psyllid removal, Las titers dropped until the 10–12th days in all three species. Following this, Las titers increased exponentially only in C. × sinensis and M. paniculata, indicating active bacterial multiplication. In C. × sinensis, Las reached a stationary phase at ∼5 log Las cells/g of tissue from the 40th day onward, while in M. paniculata, Las increased at a lower rate of up to ∼3 log Las cells/g of tissue between the 40th and 60th days, decreasing gradually thereafter and becoming undetectable from the 160th day onward. In B. koenigii, Las titers decreased from the start and remained undetectable. In C. × sinensis, an average of 2.6 log of Las cells/g of tissue was necessary for Las to move out of 50% of the NS in 23.6 days and to colonize the rest of the plant, causing a successful infection. Conversely, the probability of Las moving out of the NS remained below 50% in M. paniculata and zero in B. koenigii. To our knowledge, this is the first study on Las dynamics and whole-plant colonization during the earliest stages of infection. Identification of critical time-points for either successful multiplication or Las resistance may help to elucidate initial events of Las–host interactions that may be missed due to longer sampling intervals and at later stages of infection.
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Affiliation(s)
- Mônica Neli Alves
- Faculdade de Ciências Agrárias e Veterinárias (FCAV), Universidade Estadual Paulista (UNESP), Jaboticabal, Brazil.,Fundo de Defesa da Citricultura (Fundecitrus), Araraquara, Brazil
| | | | | | - Jesus Aparecido Ferro
- Faculdade de Ciências Agrárias e Veterinárias (FCAV), Universidade Estadual Paulista (UNESP), Jaboticabal, Brazil
| | - Leandro Peña
- Fundo de Defesa da Citricultura (Fundecitrus), Araraquara, Brazil.,Instituto de Biología Molecular y Celular de Plantas (IBMCP), Consejo Superior de Investigaciones Científicas (CSIC), Universidad Politécnica de Valencia (UPV), Valencia, Spain
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34
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Liu J, Zhang L, Yan D. Plasmodesmata-Involved Battle Against Pathogens and Potential Strategies for Strengthening Hosts. FRONTIERS IN PLANT SCIENCE 2021; 12:644870. [PMID: 34149749 PMCID: PMC8210831 DOI: 10.3389/fpls.2021.644870] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 04/28/2021] [Indexed: 06/01/2023]
Abstract
Plasmodesmata (PD) are membrane-lined pores that connect adjacent cells to mediate symplastic communication in plants. These intercellular channels enable cell-to-cell trafficking of various molecules essential for plant development and stress responses, but they can also be utilized by pathogens to facilitate their infection of hosts. Some pathogens or their effectors are able to spread through the PD by modifying their permeability. Yet plants have developed various corresponding defense mechanisms, including the regulation of PD to impede the spread of invading pathogens. In this review, we aim to illuminate the various roles of PD in the interactions between pathogens and plants during the infection process. We summarize the pathogenic infections involving PD and how the PD could be modified by pathogens or hosts. Furthermore, we propose several hypothesized and promising strategies for enhancing the disease resistance of host plants by the appropriate modulation of callose deposition and plasmodesmal permeability based on current knowledge.
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Affiliation(s)
- Jie Liu
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Lin Zhang
- Joint International Research Laboratory of Agriculture and Agri-Product Safety of the Ministry of Education, Yangzhou University, Yangzhou, China
| | - Dawei Yan
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
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35
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Khan SJ, Osborn AM, Eswara PJ. Effect of Sunlight on the Efficacy of Commercial Antibiotics Used in Agriculture. Front Microbiol 2021; 12:645175. [PMID: 34140934 PMCID: PMC8203823 DOI: 10.3389/fmicb.2021.645175] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Accepted: 04/28/2021] [Indexed: 11/13/2022] Open
Abstract
Antibiotic stewardship is of paramount importance to limit the emergence of antibiotic-resistant bacteria in not only hospital settings, but also in animal husbandry, aquaculture, and agricultural sectors. Currently, large quantities of antibiotics are applied to treat agricultural diseases like citrus greening disease (CGD). The two commonly used antibiotics approved for this purpose are streptomycin and oxytetracycline. Although investigations are ongoing to understand how efficient this process is to control the spread of CGD, to our knowledge, there have been no studies that evaluate the effect of environmental factors such as sunlight on the efficacy of the above-mentioned antibiotics. We conducted a simple disc-diffusion assay to study the efficacy of streptomycin and oxytetracycline after exposure to sunlight for 7- or 14-day periods using Escherichia coli and Bacillus subtilis as the representative strains of Gram-negative and Gram-positive organisms, respectively. Freshly prepared discs and discs stored in the dark for 7 or 14 days served as our controls. We show that the antibiotic potential of oxytetracycline exposed to sunlight dramatically decreases over the course of 14 days against both E. coli and B. subtilis. However, the effectiveness of streptomycin was only moderately impacted by sunlight. It is important to note that antibiotics that last longer in the environment may play a deleterious role in the rise and spread of antibiotic-resistant bacteria. Further studies are needed to substantively analyze the safety and efficacy of antibiotics used for broader environmental applications.
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Affiliation(s)
| | | | - Prahathees J. Eswara
- Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL, United States
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36
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Pandey SS, Nogales da Costa Vasconcelos F, Wang N. Spatiotemporal Dynamics of ' Candidatus Liberibacter asiaticus' Colonization Inside Citrus Plant and Huanglongbing Disease Development. PHYTOPATHOLOGY 2021; 111:921-928. [PMID: 33174821 DOI: 10.1094/phyto-09-20-0407-r] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
'Candidatus Liberibacter asiaticus' (CLas), the causal agent of citrus huanglongbing (HLB), colonizes inside the phloem and is naturally transmitted by the Asian citrus psyllid (ACP). Here, we investigated spatiotemporal CLas colonization in different tissues after ACP transmission. Of the nine plants successfully infected via ACP transmission, CLas was detected in the roots of all trees at 75 days postremoval of ACPs (DPR) but in the mature leaf of only one tree; this finding is consistent with the model that CLas moves passively from source to sink tissues. At 75 and 365 DPR, CLas was detected in 11.1 and 43.1% of mature leaves not fed on by ACPs during transmission, respectively, unveiling active movement to the source tissue. The difference in colonization timing of sink and source tissues indicates that CLas is capable of both passive and active movement, with passive movement being dominant. At 225 DPR, leaves fed on by ACPs during the young stage showed the highest ratio of HLB symptomatic leaves and the highest CLas titer, followed by leaves that emerged after ACP removal and mature leaves not fed on by ACPs. Importantly, our data showed that ACPs were unable to transmit CLas via feeding on mature leaves. It is estimated that it takes 3 years at most for CLas to infect the whole tree. Overall, spatiotemporal detection of CLas in different tissues after ACP transmission helps visualize the infection process of CLas in planta and subsequent HLB symptom development and provides evidence showing that young leaves should be the focus of HLB management.
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Affiliation(s)
- Sheo Shankar Pandey
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850
| | | | - Nian Wang
- Citrus Research and Education Center, Department of Microbiology and Cell Science, University of Florida, Lake Alfred, FL 33850
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37
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Li T, Zhang L, Deng Y, Deng X, Zheng Z. Establishment of a Cuscuta campestris-mediated enrichment system for genomic and transcriptomic analyses of 'Candidatus Liberibacter asiaticus'. Microb Biotechnol 2021; 14:737-751. [PMID: 33655703 PMCID: PMC7936317 DOI: 10.1111/1751-7915.13773] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 01/30/2021] [Accepted: 02/01/2021] [Indexed: 01/16/2023] Open
Abstract
‘Candidatus Liberibacter asiaticus’ (CLas) is a phloem‐limited non‐culturable α‐proteobacterium associated with citrus Huanglongbing, a highly destructive disease threatening global citrus industry. Research on CLas is challenging due to the current inability to culture CLas in vitro and the low CLas titre in citrus plant. Here, we develop a CLas enrichment system using the holoparasitic dodder plant (Cuscuta campestris) as an amenable host to acquire and enrich CLas from CLas‐infected citrus shoots maintained hydroponically. Forty‐eight out of fifty‐five (87%) dodder plants successfully parasitized CLas‐infected citrus shoots with detectable CLas by PCR. Among 48 dodders cultures, 30 showed two‐ to 419‐fold CLas titre increase as compared to the corresponding citrus hosts. The CLas population rapidly increased and reached the highest level in dodder tendrils at 15 days after parasitizing citrus shoot. Genome sequencing and assembly derived from CLas‐enriched dodder DNA samples generated a higher resolution than those obtained for CLas from citrus hosts. No genomic variation was detected in CLas after transmission from citrus to dodder during short‐term parasitism. Dual RNA‐Seq experiments showed similar CLas gene expression profiles in dodder and citrus samples, yet dodder samples generated a higher resolution of CLas transcriptome data. The ability of dodder to support CLas multiplication to high levels, as well as its advantage in CLas genomic and transcriptomic analyses, make it an optimal model for further studies on CLas–host interaction.
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Affiliation(s)
- Tao Li
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, Guangdong, 510642, China.,Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Guangdong, 510642, China
| | - Ling Zhang
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, Guangdong, 510642, China.,Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Guangdong, 510642, China
| | - Yunshuang Deng
- Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Guangdong, 510642, China
| | - Xiaoling Deng
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, Guangdong, 510642, China.,Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Guangdong, 510642, China
| | - Zheng Zheng
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, South China Agricultural University, Guangzhou, Guangdong, 510642, China.,Citrus Huanglongbing Research Laboratory, South China Agricultural University, Guangzhou, Guangdong, 510642, China
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38
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Raiol-Junior LL, Cifuentes-Arenas JC, de Carvalho EV, Girardi EA, Lopes SA. Evidence That ' Candidatus Liberibacter asiaticus' Moves Predominantly Toward New Tissue Growth in Citrus Plants. PLANT DISEASE 2021; 105:34-42. [PMID: 33201785 DOI: 10.1094/pdis-01-20-0158-re] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
'Candidatus Liberibacter asiaticus' (Las) is an unculturable, phloem-limited, insect-transmitted bacterium associated with the Asiatic form of huanglongbing (HLB), the most destructive citrus disease. In Asia and the Americas, it is transmitted by the Asian citrus psyllid (Diaphorina citri Kuwavama). Despite considerable research, little is known about the processes involved in plant infection and colonization by Las. This study was conducted to determine whether the basal portion (below girdling) of the plant is an important route for Las to move laterally from a point of inoculation on a branch to pathogen-free branches elsewhere in the canopy, and to quantify the influence of actively growing tissues on vertical upward (acropetally) or downward (basipetally) movement of Las. Nongirdled and fully or partially girdled stems of potted plants of 'Pera' sweet orange, graft-inoculated above or below girdling, were sampled in distinct regions and assessed by qPCR, 6 months postinoculation. Las invaded all regions of partially and nongirdled plants but remained restricted to the inoculated regions of fully girdled plants, evidence that in planta bacterium movement is limited to the phloem. In fully girdled plants, starch accumulated above the girdling site, probably because of changes in flow of phloem sap. To study the influence of actively growing tissues, inoculated 'Valencia' sweet orange plants were kept intact or were top- or root-pruned to force production of new tissues, and sampled at 15-day intervals. Las migrated rapidly and most predominantly toward newly developing root and leaf tissues. The rapid and predominant movement of Las to newly developed shoots and roots would explain failures of canopy heat treatments and pruning to cure HLB-affected trees, and reinforces the need to protect rapidly growing new shoots from feeding by D. citri in order to minimize transmission and spread of the pathogen by the vector within and between orchards.
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Affiliation(s)
| | | | | | - Eduardo A Girardi
- Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), Cruz das Almas BA, Brazil
| | - Silvio A Lopes
- Fundo de Defesa da Citricultura (Fundecitrus), Araraquara SP, Brazil
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39
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Irigoyen S, Ramasamy M, Pant S, Niraula P, Bedre R, Gurung M, Rossi D, Laughlin C, Gorman Z, Achor D, Levy A, Kolomiets MV, Sétamou M, Badillo-Vargas IE, Avila CA, Irey MS, Mandadi KK. Plant hairy roots enable high throughput identification of antimicrobials against Candidatus Liberibacter spp. Nat Commun 2020; 11:5802. [PMID: 33199718 PMCID: PMC7669877 DOI: 10.1038/s41467-020-19631-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 10/26/2020] [Indexed: 12/20/2022] Open
Abstract
A major bottleneck in identifying therapies to control citrus greening and other devastating plant diseases caused by fastidious pathogens is our inability to culture the pathogens in defined media or axenic cultures. As such, conventional approaches for antimicrobial evaluation (genetic or chemical) rely on time-consuming, low-throughput and inherently variable whole-plant assays. Here, we report that plant hairy roots support the growth of fastidious pathogens like Candidatus Liberibacter spp., the presumptive causal agents of citrus greening, potato zebra chip and tomato vein greening diseases. Importantly, we leverage the microbial hairy roots for rapid, reproducible efficacy screening of multiple therapies. We identify six antimicrobial peptides, two plant immune regulators and eight chemicals which inhibit Candidatus Liberibacter spp. in plant tissues. The antimicrobials, either singly or in combination, can be used as near- and long-term therapies to control citrus greening, potato zebra chip and tomato vein greening diseases.
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Affiliation(s)
- Sonia Irigoyen
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
| | | | - Shankar Pant
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
- Agricultural Research Service, US Department of Agriculture, Stillwater, OK, USA
| | - Prakash Niraula
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
| | - Renesh Bedre
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
| | - Meena Gurung
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
| | - Denise Rossi
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
| | - Corinne Laughlin
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
| | - Zachary Gorman
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA
| | - Diann Achor
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA
| | - Amit Levy
- Citrus Research and Education Center, University of Florida, Lake Alfred, FL, USA
- Department of Plant Pathology, University of Florida, Gainesville, FL, USA
| | - Michael V Kolomiets
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA
| | - Mamoudou Sétamou
- Texas A&M University-Kingsville, Citrus Center, Weslaco, TX, USA
| | - Ismael E Badillo-Vargas
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
- Department of Entomology, Texas A&M University, College Station, TX, USA
| | - Carlos A Avila
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA
- Department of Horticultural Sciences, Texas A&M University, College Station, TX, USA
| | | | - Kranthi K Mandadi
- Texas A&M AgriLife Research and Extension Center, Weslaco, TX, USA.
- Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA.
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40
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Zhang J, Coaker G, Zhou JM, Dong X. Plant Immune Mechanisms: From Reductionistic to Holistic Points of View. MOLECULAR PLANT 2020; 13:1358-1378. [PMID: 32916334 PMCID: PMC7541739 DOI: 10.1016/j.molp.2020.09.007] [Citation(s) in RCA: 67] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 09/05/2020] [Accepted: 09/08/2020] [Indexed: 05/19/2023]
Abstract
After three decades of the amazing progress made on molecular studies of plant-microbe interactions (MPMI), we have begun to ask ourselves "what are the major questions still remaining?" as if the puzzle has only a few pieces missing. Such an exercise has ultimately led to the realization that we still have many more questions than answers. Therefore, it would be an impossible task for us to project a coherent "big picture" of the MPMI field in a single review. Instead, we provide our opinions on where we would like to go in our research as an invitation to the community to join us in this exploration of new MPMI frontiers.
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Affiliation(s)
- Jie Zhang
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; CAS Center for Excellence in Biotic Interactions, College of Advanced Agricutural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Gitta Coaker
- Department of Plant Pathology, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Jian-Min Zhou
- CAS Center for Excellence in Biotic Interactions, College of Advanced Agricutural Sciences, University of Chinese Academy of Sciences, Beijing 100049, China; State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Xinnian Dong
- Howard Hughes Medical Institute, Duke University, Durham, NC 27708, USA; Department of Biology, Duke University, PO Box 90338, Durham, NC 27708, USA.
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Huang W, Reyes-Caldas P, Mann M, Seifbarghi S, Kahn A, Almeida RPP, Béven L, Heck M, Hogenhout SA, Coaker G. Bacterial Vector-Borne Plant Diseases: Unanswered Questions and Future Directions. MOLECULAR PLANT 2020; 13:1379-1393. [PMID: 32835885 PMCID: PMC7769051 DOI: 10.1016/j.molp.2020.08.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 08/18/2020] [Accepted: 08/18/2020] [Indexed: 06/01/2023]
Abstract
Vector-borne plant diseases have significant ecological and economic impacts, affecting farm profitability and forest composition throughout the world. Bacterial vector-borne pathogens have evolved sophisticated strategies to interact with their hemipteran insect vectors and plant hosts. These pathogens reside in plant vascular tissue, and their study represents an excellent opportunity to uncover novel biological mechanisms regulating intracellular pathogenesis and to contribute to the control of some of the world's most invasive emerging diseases. In this perspective, we highlight recent advances and major unanswered questions in the realm of bacterial vector-borne disease, focusing on liberibacters, phytoplasmas, spiroplasmas, and Xylella fastidiosa.
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Affiliation(s)
- Weijie Huang
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Paola Reyes-Caldas
- Department of Plant Pathology, University of California, Davis, CA, 95616, USA
| | - Marina Mann
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, USA
| | - Shirin Seifbarghi
- Department of Plant Pathology, University of California, Davis, CA, 95616, USA
| | - Alexandra Kahn
- Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA
| | - Rodrigo P P Almeida
- Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA
| | - Laure Béven
- UMR 1332 Biologie du Fruit et Pathologie, Univ. Bordeaux, INRAE, Villenave d'Ornon 33882 France
| | - Michelle Heck
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, USA; Boyce Thompson Institute, Ithaca, NY 14853, USA; Emerging Pests and Pathogens Research Unit, Robert W. Holley Center, USDA ARS, Ithaca, NY 14853, USA
| | - Saskia A Hogenhout
- Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK; School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Gitta Coaker
- Department of Plant Pathology, University of California, Davis, CA, 95616, USA.
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