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Ekanayake G, Gohmann R, Mackey D. A method for quantitation of apoplast hydration in Arabidopsis leaves reveals water-soaking activity of effectors of Pseudomonas syringae during biotrophy. Sci Rep 2022; 12:18363. [PMID: 36319664 PMCID: PMC9626588 DOI: 10.1038/s41598-022-22472-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2022] [Accepted: 10/14/2022] [Indexed: 12/03/2022] Open
Abstract
The plant apoplast has a crucial role in photosynthesis and respiration due to its vital function in gas exchange and transpiration. The apoplast is also a dynamic environment that participates in many ion and nutrient transport processes via plasma membrane-localized proteins. Furthermore, diverse microbes colonize the plant apoplast, including the hemibiotrophic bacterial pathogen, Pseudomonas syringae pv. tomato (Pto) strain DC3000. Pto DC3000 initiates pathogenesis upon moving through stomata into the apoplast and then proliferating to high levels. Here we developed a centrifugation-based method to isolate and quantify the apoplast fluid in Arabidopsis leaves, without significantly damaging the tissue. We applied the simple apoplast extraction method to demonstrate that the Pto DC3000 type III bacterial effectors AvrE1 and HopM1 induce hydration of the Arabidopsis apoplast in advance of macroscopic water-soaking, disruption of host cell integrity, and disease progression. Finally, we demonstrate the utility of the apoplast extraction method for isolation of bacteria proliferating in the apoplast.
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Affiliation(s)
- Gayani Ekanayake
- Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH, 43210, USA
| | - Reid Gohmann
- Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH, 43210, USA
- Molecular, Cellular, and Developmental Biology Program, Ohio State University, Columbus, OH, 43210, USA
| | - David Mackey
- Department of Horticulture and Crop Science, The Ohio State University, Columbus, OH, 43210, USA.
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, 43210, USA.
- Center for Applied Plant Sciences, The Ohio State University, Columbus, OH, 43210, USA.
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2
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Ye JY, Zhou M, Zhu QY, Zhu YX, Du WX, Liu XX, Jin CW. Inhibition of shoot-expressed NRT1.1 improves reutilization of apoplastic iron under iron-deficient conditions. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 112:549-564. [PMID: 36062335 DOI: 10.1111/tpj.15967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 08/14/2022] [Accepted: 08/31/2022] [Indexed: 06/15/2023]
Abstract
Iron deficiency is a major constraint for plant growth in calcareous soils. The interplay between NO3 - and Fe nutrition affects plant performance under Fe-deficient conditions. However, how NO3 - negatively regulates Fe nutrition at the molecular level in plants remains elusive. Here, we showed that the key nitrate transporter NRT1.1 in Arabidopsis plants, especially in the shoots, was markedly downregulated at post-translational levels by Fe deficiency. However, loss of NRT1.1 function alleviated Fe deficiency chlorosis, suggesting that downregulation of NRT1.1 by Fe deficiency favors plant tolerance to Fe deficiency. Further analysis showed that although disruption of NRT1.1 did not alter Fe levels in both the shoots and roots, it improved the reutilization of apoplastic Fe in shoots but not in roots. In addition, disruption of NRT1.1 prevented Fe deficiency-induced apoplastic alkalization in shoots by inhibiting apoplastic H+ depletion via NO3 - uptake. In vitro analysis showed that reduced pH facilitates release of cell wall-bound Fe. Thus, foliar spray with an acidic buffer promoted the reutilization of Fe in the leaf apoplast to enhance plant tolerance to Fe deficiency, while the opposite was true for the foliar spray with a neutral buffer. Thus, downregulation of the shoot-part function of NRT1.1 prevents apoplastic alkalization to ensure the reutilization of apoplastic Fe under Fe-deficient conditions. Our findings may provide a basis for elucidating the link between N and Fe nutrition in plants and insight to scrutinize the relevance of shoot-expressed NRT1.1 to the plant response to stress.
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Affiliation(s)
- Jia Yuan Ye
- State Key Laboratory of Plant Physiology and Biochemistry, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, 310058, China
| | - Miao Zhou
- State Key Laboratory of Plant Physiology and Biochemistry, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, 310058, China
| | - Qing Yang Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, 310058, China
| | - Ya Xin Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, 310058, China
| | - Wen Xin Du
- State Key Laboratory of Plant Physiology and Biochemistry, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, 310058, China
| | - Xing Xing Liu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, 310058, China
| | - Chong Wei Jin
- State Key Laboratory of Plant Physiology and Biochemistry, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou, 310058, China
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3
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Figueiredo J, Cavaco AR, Guerra-Guimarães L, Leclercq C, Renaut J, Cunha J, Eiras-Dias J, Cordeiro C, Matos AR, Sousa Silva M, Figueiredo A. An apoplastic fluid extraction method for the characterization of grapevine leaves proteome and metabolome from a single sample. PHYSIOLOGIA PLANTARUM 2021; 171:343-357. [PMID: 32860657 DOI: 10.1111/ppl.13198] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 08/19/2020] [Accepted: 08/20/2020] [Indexed: 05/23/2023]
Abstract
The analysis of complex biological systems keeps challenging researchers. The main goal of systems biology is to decipher interactions within cells, by integrating datasets from large scale analytical approaches including transcriptomics, proteomics and metabolomics and more specialized 'OMICS' such as epigenomics and lipidomics. Studying different cellular compartments allows a broader understanding of cell dynamics. Plant apoplast, the cellular compartment external to the plasma membrane including the cell wall, is particularly demanding to analyze. Despite our knowledge on apoplast involvement on several processes from cell growth to stress responses, its dynamics is still poorly known due to the lack of efficient extraction processes adequate to each plant system. Analyzing woody plants such as grapevine raises even more challenges. Grapevine is among the most important fruit crops worldwide and a wider characterization of its apoplast is essential for a deeper understanding of its physiology and cellular mechanisms. Here, we describe, for the first time, a vacuum-infiltration-centrifugation method that allows a simultaneous extraction of grapevine apoplastic proteins and metabolites from leaves on a single sample, compatible with high-throughput mass spectrometry analyses. The extracted apoplast from two grapevine cultivars, Vitis vinifera cv 'Trincadeira' and 'Regent', was directly used for proteomics and metabolomics analysis. The proteome was analyzed by nanoLC-MS/MS and more than 700 common proteins were identified, with highly diverse biological functions. The metabolome profile through FT-ICR-MS allowed the identification of 514 unique putative compounds revealing a broad spectrum of molecular classes.
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Affiliation(s)
- Joana Figueiredo
- University of Lisboa, Faculty of Sciences, BioISI - Biosystems & Integrative Sciences Institute, Lisbon, Portugal
- Laboratório de FTICR e Espectrometria de Massa Estrutural, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
| | - Ana Rita Cavaco
- University of Lisboa, Faculty of Sciences, BioISI - Biosystems & Integrative Sciences Institute, Lisbon, Portugal
| | - Leonor Guerra-Guimarães
- Centro de Investigação das Ferrugens do Cafeeiro, Instituto Superior de Agronomia, Universidade de Lisboa, Oeiras, Portugal
- Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia, Universidade de Lisboa, Lisbon, Portugal
| | - Céline Leclercq
- Luxembourg Institute of Science and Technology, Belvaux, Luxembourg
| | - Jenny Renaut
- Luxembourg Institute of Science and Technology, Belvaux, Luxembourg
| | - Jorge Cunha
- Instituto Nacional de Investigação Agrária e Veterinária - Estação Vitivinícola Nacional, Dois Portos, Portugal
| | - José Eiras-Dias
- Instituto Nacional de Investigação Agrária e Veterinária - Estação Vitivinícola Nacional, Dois Portos, Portugal
| | - Carlos Cordeiro
- Laboratório de FTICR e Espectrometria de Massa Estrutural, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
| | - Ana Rita Matos
- University of Lisboa, Faculty of Sciences, BioISI - Biosystems & Integrative Sciences Institute, Lisbon, Portugal
| | - Marta Sousa Silva
- Laboratório de FTICR e Espectrometria de Massa Estrutural, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
- Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal
| | - Andreia Figueiredo
- University of Lisboa, Faculty of Sciences, BioISI - Biosystems & Integrative Sciences Institute, Lisbon, Portugal
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4
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Lim SD, Mayer JA, Yim WC, Cushman JC. Plant tissue succulence engineering improves water-use efficiency, water-deficit stress attenuation and salinity tolerance in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2020; 103:1049-1072. [PMID: 32338788 DOI: 10.1111/tpj.14783] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 04/01/2020] [Accepted: 04/14/2020] [Indexed: 05/25/2023]
Abstract
Tissue succulence (ratio of tissue water/leaf area or dry mass) or the ability to store water within living tissues is among the most successful adaptations to drought in the plant kingdom. This taxonomically widespread adaptation helps plants avoid the damaging effects of drought, and is often associated with the occupancy of epiphytic, epilithic, semi-arid and arid environments. Tissue succulence was engineered in Arabidopsis thaliana by overexpression of a codon-optimized helix-loop-helix transcription factor (VvCEB1opt ) from wine grape involved in the cell expansion phase of berry development. VvCEB1opt -overexpressing lines displayed significant increases in cell size, succulence and decreased intercellular air space. VvCEB1opt -overexpressing lines showed increased instantaneous and integrated water-use efficiency (WUE) due to reduced stomatal conductance caused by reduced stomatal aperture and density resulting in increased attenuation of water-deficit stress. VvCEB1opt -overexpressing lines also showed increased salinity tolerance due to reduced salinity uptake and dilution of internal Na+ and Cl- as well as other ions. Alterations in transporter activities were further suggested by media and apoplastic acidification, hygromycin B tolerance and changes in relative transcript abundance patterns of various transporters with known functions in salinity tolerance. Engineered tissue succulence might provide an effective strategy for improving WUE, drought avoidance or attenuation, salinity tolerance, and for crassulacean acid metabolism biodesign.
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Affiliation(s)
- Sung Don Lim
- Department of Applied Plant Sciences, Kangwon National University, Chuncheon, 24341, Republic of Korea
| | | | - Won Cheol Yim
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, 89557-0330, USA
| | - John C Cushman
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV, 89557-0330, USA
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5
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Dang X, Chen B, Liu F, Ren H, Liu X, Zhou J, Qin Y, Lin D. Auxin Signaling-Mediated Apoplastic pH Modification Functions in Petal Conical Cell Shaping. Cell Rep 2020; 30:3904-3916.e3. [DOI: 10.1016/j.celrep.2020.02.087] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 08/02/2019] [Accepted: 02/24/2020] [Indexed: 12/31/2022] Open
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6
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Zeng S, Liu D, Li C, Yu F, Fan L, Lei C, Huang Y, Nie Z, Yao S. Cell-Surface-Anchored Ratiometric DNA Tweezer for Real-Time Monitoring of Extracellular and Apoplastic pH. Anal Chem 2018; 90:13459-13466. [DOI: 10.1021/acs.analchem.8b03299] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Shu Zeng
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
| | - Dan Liu
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
| | - Chiyu Li
- College of Biology, Hunan University, Changsha 410082, PR China
| | - Feng Yu
- College of Biology, Hunan University, Changsha 410082, PR China
| | - Lin Fan
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
| | - Chunyang Lei
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
| | - Yan Huang
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
| | - Zhou Nie
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
| | - Shouzhuo Yao
- State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan Provincial Key Laboratory of Biomacromolecular Chemical Biology, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China
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7
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Arsuffi G, Braybrook SA. Acid growth: an ongoing trip. JOURNAL OF EXPERIMENTAL BOTANY 2018; 69:137-146. [PMID: 29211894 DOI: 10.1093/jxb/erx390] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Accepted: 10/13/2017] [Indexed: 06/07/2023]
Abstract
Since its first formulation almost 50 years ago, acid growth has had a chequered past complicated by utilization of diverse species and organs for testing alongside necessary but coarse methodology. Within the past 25 years, we have gained new insights into the molecular mechanisms behind the transduction of the signal auxin into the reality of an apoplastic pH shift as well as the effect on cell wall mechanics and the biochemical players within the wall contributing to the resultant growth. In this review, we begin by discussing the historical work and its complications, move on to the modern work and its addition to acid growth, which we finally summarize in an updated model which includes new postulations and questions.
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8
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Geilfus CM. The pH of the Apoplast: Dynamic Factor with Functional Impact Under Stress. MOLECULAR PLANT 2017; 10:1371-1386. [PMID: 28987886 DOI: 10.1016/j.molp.2017.09.018] [Citation(s) in RCA: 103] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 09/22/2017] [Accepted: 09/30/2017] [Indexed: 05/23/2023]
Abstract
The apoplast is an interconnected compartment with a thin water-film that alkalinizes under stress. This systemic pH increase may be a secondary effect without functional implications, arising from ion movements or proton-pump regulations. On the other hand, there are increasing indications that it is part of a mechanism to withstand stress. Regardless of this controversy, alkalinization of the apoplast has received little attention. The apoplastic pH (pHapo) increases not only during plant-pathogen interactions but also in response to salinity or drought. Not much is known about the mechanisms that cause the leaf apoplast to alkalinize, nor whether, and if so, how functional impact is conveyed. Controversial explanations have been given, and the unusual complexity of pHapo regulation is considered as the primary reason behind this lack of knowledge. A gathering of scattered information revealed that changes in pHapo convey functionality by regulating stomatal aperture via the effects exerted on abscisic acid. Moreover, apoplastic alkalinization may regulate growth under stress, whereas this needs to be verified. In this review, a comprehensive survey about several physiological mechanisms that alkalize the apoplast under stress is given, and the suitability of apoplastic alkalinization as transducing element for the transmission of sensory information is discussed.
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Affiliation(s)
- Christoph-Martin Geilfus
- Division of Controlled Environment Horticulture, Faculty of Life Sciences, Albrecht Daniel Thaer-Institute of Agricultural and Horticultural Sciences, Humboldt-University of Berlin, Albrecht-Thaer-Weg 1, 14195 Berlin, Germany.
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9
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Lee MH, Yoo YJ, Kim DH, Hanh NH, Kwon Y, Hwang I. The Prenylated Rab GTPase Receptor PRA1.F4 Contributes to Protein Exit from the Golgi Apparatus. PLANT PHYSIOLOGY 2017; 174:1576-1594. [PMID: 28487479 PMCID: PMC5490915 DOI: 10.1104/pp.17.00466] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 05/04/2017] [Indexed: 05/28/2023]
Abstract
Prenylated Rab acceptor1 (PRA1) functions in the recruitment of prenylated Rab proteins to their cognate organelles. Arabidopsis (Arabidopsis thaliana) contains a large number of proteins belonging to the AtPRA1 family. However, their physiological roles remain largely unknown. Here, we investigated the physiological role of AtPRA1.F4, a member of the AtPRA1 family. A T-DNA insertion knockdown mutant of AtPRA1.F4, atpra1.f4, was smaller in stature than parent plants and possessed shorter roots, whereas transgenic plants overexpressing HA:AtPRA1.F4 showed enhanced development of secondary roots and root hairs. However, both overexpression and knockdown plants exhibited increased sensitivity to high-salt stress, lower vacuolar Na+/K+-ATPase and plasma membrane ATPase activities, lower and higher pH in the vacuole and apoplast, respectively, and highly vesiculated Golgi apparatus. HA:AtPRA1.F4 localized to the Golgi apparatus and assembled into high-molecular-weight complexes. atpra1.f4 plants displayed a defect in vacuolar trafficking, which was complemented by low but not high levels of HA:AtPRA1.F4 Overexpression of HA:AtPRA1.F4 also inhibited protein trafficking at the Golgi apparatus, albeit differentially depending on the final destination or type of protein: trafficking of vacuolar proteins, plasma membrane proteins, and trans-Golgi network (TGN)-localized SYP61 was strongly inhibited; trafficking of TGN-localized SYP51 was slightly inhibited; and trafficking of secretory proteins and TGN-localized SYP41 was negligibly or not significantly inhibited. Based on these results, we propose that Golgi-localized AtPRA1.F4 is involved in the exit of many but not all types of post-Golgi proteins from the Golgi apparatus. Additionally, an appropriate level of AtPRA1.F4 is crucial for its function at the Golgi apparatus.
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Affiliation(s)
- Myoung Hui Lee
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Yun-Joo Yoo
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Dae Heon Kim
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Nguyen Hong Hanh
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Yun Kwon
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Inhwan Hwang
- Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
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Auxin steers root cell expansion via apoplastic pH regulation in Arabidopsis thaliana. Proc Natl Acad Sci U S A 2017; 114:E4884-E4893. [PMID: 28559333 DOI: 10.1073/pnas.1613499114] [Citation(s) in RCA: 197] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Plant cells are embedded within cell walls, which provide structural integrity, but also spatially constrain cells, and must therefore be modified to allow cellular expansion. The long-standing acid growth theory postulates that auxin triggers apoplast acidification, thereby activating cell wall-loosening enzymes that enable cell expansion in shoots. Interestingly, this model remains heavily debated in roots, because of both the complex role of auxin in plant development as well as technical limitations in investigating apoplastic pH at cellular resolution. Here, we introduce 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) as a suitable fluorescent pH indicator for assessing apoplastic pH, and thus acid growth, at a cellular resolution in Arabidopsis thaliana roots. Using HPTS, we demonstrate that cell wall acidification triggers cellular expansion, which is correlated with a preceding increase of auxin signaling. Reduction in auxin levels, perception, or signaling abolishes both the extracellular acidification and cellular expansion. These findings jointly suggest that endogenous auxin controls apoplastic acidification and the onset of cellular elongation in roots. In contrast, an endogenous or exogenous increase in auxin levels induces a transient alkalinization of the extracellular matrix, reducing cellular elongation. The receptor-like kinase FERONIA is required for this physiological process, which affects cellular root expansion during the gravitropic response. These findings pinpoint a complex, presumably concentration-dependent role for auxin in apoplastic pH regulation, steering the rate of root cell expansion and gravitropic response.
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Bredow M, Vanderbeld B, Walker VK. Ice-binding proteins confer freezing tolerance in transgenic Arabidopsis thaliana. PLANT BIOTECHNOLOGY JOURNAL 2017; 15:68-81. [PMID: 27317906 PMCID: PMC5253476 DOI: 10.1111/pbi.12592] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 05/30/2016] [Accepted: 06/10/2016] [Indexed: 05/07/2023]
Abstract
Lolium perenne is a freeze-tolerant perennial ryegrass capable of withstanding temperatures below -13 °C. Ice-binding proteins (IBPs) presumably help prevent damage associated with freezing by restricting the growth of ice crystals in the apoplast. We have investigated the expression, localization and in planta freezing protection capabilities of two L. perenne IBP isoforms, LpIRI2 and LpIRI3, as well as a processed IBP (LpAFP). One of these isoforms, LpIRI2, lacks a conventional signal peptide and was assumed to be a pseudogene. Nevertheless, both LpIRI2 and LpIRI3 transcripts were up-regulated following cold acclimation. LpIRI2 also demonstrated ice-binding activity when produced recombinantly in Escherichia coli. Both the LpIRI3 and LpIRI2 isoforms appeared to accumulate in the apoplast of transgenic Arabidopsis thaliana plants. In contrast, the fully processed isoform, LpAFP, remained intracellular. Transgenic plants expressing either LpIRI2 or LpIRI3 showed reduced ion leakage (12%-39%) after low-temperature treatments, and significantly improved freezing survival, while transgenic LpAFP-expressing lines did not confer substantial subzero protection. Freeze protection was further enhanced by with the introduction of more than one IBP isoform; ion leakage was reduced 26%-35% and 10% of plants survived temperatures as low as -8 °C. Our results demonstrate that apoplastic expression of multiple L. perenne IBP isoforms shows promise for providing protection to crops susceptible to freeze-induced damage.
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Affiliation(s)
| | | | - Virginia K. Walker
- Department of BiologyQueen's UniversityKingstonONCanada
- Department of Biomedical and Molecular Sciences and School of Environmental StudiesQueen's UniversityKingstonONCanada
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