Proteomic and phytohormone analysis of the response of maize (Zea mays L.) seedlings to sugarcane mosaic virus

Identification and characterization of the Remorin gene family in Saccharum and the involvement of ScREM1.5e-1/-2 in SCMV infection on sugarcane

Introduction

Remorins (REMs) are plant-specific membrane-associated proteins that play important roles in plant-pathogen interactions and environmental adaptations. Group I REMs are extensively involved in virus infection. However, little is known about the REM gene family in sugarcane (Saccharum spp. hyrid), the most important sugar and energy crop around world.

Methods

Comparative genomics were employed to analyze the REM gene family in Saccharum spontaneum. Transcriptomics or RT-qPCR were used to analyze their expression files in different development stages or tissues under different treatments. Yeast two hybrid, bimolecular fluorescence complementation and co-immunoprecipitation assays were applied to investigate the protein interaction.

Results

In this study, 65 REMs were identified from Saccharum spontaneum genome and classified into six groups based on phylogenetic tree analysis. These REMs contain multiple cis-elements associated with growth, development, hormone and stress response. Expression profiling revealed that among different SsREMs with variable expression levels in different developmental stages or different tissues. A pair of alleles, ScREM1.5e-1/-2, were isolated from the sugarcane cultivar ROC22. ScREM1.5e-1/-2 were highly expressed in leaves, with the former expressed at significantly higher levels than the latter. Their expression was induced by treatment with H2O2, ABA, ethylene, brassinosteroid, SA or MeJA, and varied upon Sugarcane mosaic virus (SCMV) infection. ScREM1.5e-1 was localized to the plasma membrane (PM), while ScREM1.5e-2 was localized to the cytoplasm or nucleus. ScREM1.5e-1/-2 can self-interact and interact with each other, and interact with VPgs from SCMV, Sorghum mosaic virus, or Sugarcane streak mosaic virus. The interactions with VPgs relocated ScREM1.5e-1 from the PM to the cytoplasm.

Discussion

These results reveal the origin, distribution and evolution of the REM gene family in sugarcane and may shed light on engineering sugarcane resistance against sugarcane mosaic pathogens.

Integrated transcriptome and microRNA sequencing analyses reveal gene responses in poplar leaves infected by the novel pathogen bean common mosaic virus (BCMV)

Recently, a novel poplar mosaic disease caused by bean common mosaic virus (BCMV) was investigated in Populus alba var. pyramidalis in China. Symptom characteristics, physiological performance of the host, histopathology, genome sequences and vectors, and gene regulation at the transcriptional and posttranscriptional levels were analyzed and RT-qPCR (quantitative reverse transcription PCR) validation of expression was performed in our experiments. In this work, the mechanisms by which the BCMV pathogen impacts physiological performance and the molecular mechanisms of the poplar response to viral infection were reported. The results showed that BCMV infection decreased the chlorophyll content, inhibited the net photosynthesis rate (Pn) and stomatal conductance (Gs), and significantly changed chlorophyll fluorescence parameters in diseased leaves. Transcriptome analysis revealed that the expression of the majority of DEGs (differentially expressed genes) involved in the flavonoid biosynthesis pathway was promoted, but the expression of all or almost all DEGs associated with photosynthesis-antenna proteins and the photosynthesis pathway was inhibited in poplar leaves, suggesting that BCMV infection increased the accumulation of flavonoids but decreased photosynthesis in hosts. Gene set enrichment analysis (GSEA) illustrated that viral infection promoted the expression of genes involved in the defense response or plant-pathogen interaction. MicroRNA-seq analysis illustrated that 10 miRNA families were upregulated while 6 families were downregulated in diseased poplar leaves; moreover, miR156, the largest family with the most miRNA members and target genes, was only differentially upregulated in long-period disease (LD) poplar leaves. Integrated transcriptome and miRNA-seq analyses revealed 29 and 145 candidate miRNA-target gene pairs; however, only 17 and 76 pairs, accounting for 2.2% and 3.2% of all DEGs, were authentically negatively regulated in short-period disease (SD) and LD leaves, respectively. Interestingly, 4 miR156/SPL (squamosa promoter-binding-like protein) miRNA-target gene pairs were identified in LD leaves: the miR156 molecules were upregulated, but SPL genes were downregulated. In conclusion, BCMV infection significantly changed transcriptional and posttranscriptional gene expression in poplar leaves, inhibited photosynthesis, increased the accumulation of flavonoids, induced systematic mosaic symptoms, and decreased physiological performance in diseased poplar leaves. This study elucidated the fine-tuned regulation of poplar gene expression by BCMV; moreover, the results also suggested that miR156/SPL modules played important roles in the virus response and development of viral systematic symptoms in plant virus disease.

Analysis of proteomic changes in cassava cv. Kasetsart 50 caused by Sri Lankan cassava mosaic virus infection

BACKGROUND

Sri Lankan cassava mosaic virus (SLCMV) is a plant virus causing significant economic losses throughout Southeast Asia. While proteomics has the potential to identify molecular markers that could assist the breeding of virus resistant cultivars, the effects of SLCMV infection in cassava have not been previously explored in detail.

RESULTS

Liquid Chromatography-Tandem Mass Spectrometry (LC/MS-MS) was used to identify differentially expressed proteins in SLCMV infected leaves, and qPCR was used to confirm changes at mRNA levels. LC/MS-MS identified 1,813 proteins, including 479 and 408 proteins that were upregulated in SLCMV-infected and healthy cassava plants respectively, while 109 proteins were detected in both samples. Most of the identified proteins were involved in biosynthetic processes (29.8%), cellular processes (20.9%), and metabolism (18.4%). Transport proteins, stress response molecules, and proteins involved in signal transduction, plant defense responses, photosynthesis, and cellular respiration, although present, only represented a relatively small subset of the detected differences. RT-qPCR confirmed the upregulation of WRKY 77 (A0A140H8T1), WRKY 83 (A0A140H8T7), NAC 6 (A0A0M4G3M4), NAC 35 (A0A0M5JAB4), NAC 22 (A0A0M5J8Q6), NAC 54 (A0A0M4FSG8), NAC 70 (A0A0M4FEU9), MYB (A0A2C9VER9 and A0A2C9VME6), bHLH (A0A2C9UNL9 and A0A2C9WBZ1) transcription factors. Additional upregulated transcripts included receptors, such as receptor-like serine/threonine-protein kinase (RSTK) (A0A2C9UPE4), Toll/interleukin-1 receptor (TIR) (A0A2C9V5Q3), leucine rich repeat N-terminal domain (LRRNT_2) (A0A2C9VHG8), and cupin (A0A199UBY6). These molecules participate in innate immunity, plant defense mechanisms, and responses to biotic stress and to phytohormones.

CONCLUSIONS

We detected 1,813 differentially expressed proteins infected cassava plants, of which 479 were selectively upregulated. These could be classified into three main biological functional groups, with roles in gene regulation, plant defense mechanisms, and stress responses. These results will help identify key proteins affected by SLCMV infection in cassava plants.

Comparative proteomics combined with analyses of transgenic plants reveal ZmREM1.3 mediates maize resistance to southern corn rust

Southern corn rust (SCR), which is a destructive disease caused by Puccinia polysora Underw. (P. polysora), commonly occurs in warm-temperate and tropical regions. To identify candidate proteins related to SCR resistance and characterize the molecular mechanisms underlying the maize-P. polysora interaction, a comparative proteomic analysis of susceptible and resistant maize lines was performed. Statistical analyses revealed 1489 differentially abundant proteins in the resistant line, as well as 1035 differentially abundant proteins in the susceptible line. After the P. polysora infection, the abundance of one remorin protein (ZmREM1.3) increased in the resistant genotype, but decreased in the susceptible genotype. Plant-specific remorins are important for responses to microbial infections as well as plant signalling processes. In this study, transgenic maize plants overexpressing ZmREM1.3 exhibited enhanced resistance to the biotrophic P. polysora. In contrast, homozygous ZmREM1.3 UniformMu mutant plants were significantly more susceptible to P. polysora than wild-type plants. Additionally, the ZmREM1.3-overexpressing plants accumulated more salicylic acid (SA) and jasmonic acid (JA). Moreover, the expression levels of defence-related genes were higher in ZmREM1.3-overexpressing maize plants than in non-transgenic control plants in response to the P. polysora infection. Overall, our results provide evidence that ZmREM1.3 positively regulates maize defences against P. polysora likely via SA/JA-mediated defence signalling pathways. This study represents the first large-scale proteomic analysis of the molecular mechanisms underlying the maize-P. polysora interaction. This is also the first report confirming the remorin protein family affects plant resistance to SCR.

Maize phenylalanine ammonia-lyases contribute to resistance to Sugarcane mosaic virus infection, most likely through positive regulation of salicylic acid accumulation

Sugarcane mosaic virus (SCMV) is a pathogen of worldwide importance that causes dwarf mosaic disease on maize (Zea mays). Until now, few maize genes/proteins have been shown to be involved in resistance to SCMV. In this study, we characterized the role of maize phenylalanine ammonia-lyases (ZmPALs) in accumulation of the defence signal salicylic acid (SA) and in resistance to virus infection. SCMV infection significantly increased SA accumulation and expression of SA-responsive pathogenesis-related protein genes (PRs). Interestingly, exogenous SA treatment decreased SCMV accumulation and enhanced resistance. Both reverse transcription-coupled quantitative PCR and RNA-Seq data confirmed that expression levels of at least four ZmPAL genes were significantly up-regulated upon SCMV infection. Knockdown of ZmPAL expression led to enhanced SCMV infection symptom severity and virus multiplication, and simultaneously resulted in decreased SA accumulation and PR gene expression. Intriguingly, application of exogenous SA to SCMV-infected ZmPAL-silenced maize plants decreased SCMV accumulation, showing that ZmPALs are required for SA-mediated resistance to SCMV infection. In addition, lignin measurements and metabolomic analysis showed that ZmPALs are also involved in SCMV-induced lignin accumulation and synthesis of other secondary metabolites via the phenylpropanoid pathway. In summary, our results indicate that ZmPALs are required for SA accumulation in maize and are involved in resistance to virus infection by limiting virus accumulation and moderating symptom severity.

The Involvement of Jasmonic Acid, Ethylene, and Salicylic Acid in the Signaling Pathway of Clonostachys rosea-Induced Resistance to Gray Mold Disease in Tomato

Tomato gray mold disease caused by Botrytis cinerea is a serious disease that threatens tomato production around the world. Clonostachys rosea has been used successfully as a biocontrol agent against divergent plant pathogens, including B. cinerea. To understand the signal transduction pathway of C. rosea-induced resistance to tomato gray mold disease, the effects of C. rosea on gray mold tomato leaves along with changes in the activities of three defense enzymes (phenylalanine ammonialyase [PAL], polyphenol oxidase [PPO], and catalase [CAT]), second messengers (nitric oxide [NO], hydrogen peroxide [H₂O₂], and superoxide anion radical [O₂^-]), and stress-related genes (mitogen-activated protein kinase [MAPK], WRKY, Lexyl2, and atpA) in four different hormone-deficient (jasmonic acid [JA], ethylene [ET], salicylic acid [SA], and gibberellin) tomato mutants were investigated. The results revealed that C. rosea significantly inhibited the growth of mycelia and spore germination of B. cinerea. Furthermore, it reduced the incidence of gray mold disease, induced higher levels of PAL and PPO, and induced lower levels of CAT activities in tomato leaves. Moreover, it also increased NO, H₂O₂, and O₂^- levels and the gene expression levels of WRKY, MAPK, atpA, and Lexyl2. The incidence of gray mold disease in four hormone-deficient mutants was higher than that in the corresponding wild-type tomato plants. Among all of these hormone-deficient tomato mutants, JA had the most significant effect in regulating the different signal molecules. Additional study suggested that JA upregulated the expression of Lexyl2, MAPK, and WRKY but downregulated atpA. Furthermore, JA also enhanced the activity of PAL, PPO, and CAT and the production of NO and H₂O₂. SA downregulated CAT and PAL, whereas ET upregulated PAL but downregulated CAT. This study is of significance in understanding the regulatory pathways and biocontrol mechanism of C. rosea against B. cinerea.

Glutathione S-Transferase Enzymes in Plant-Pathogen Interactions

Plant glutathione S-transferases (GSTs) are ubiquitous and multifunctional enzymes encoded by large gene families. A characteristic feature of GST genes is their high inducibility by a wide range of stress conditions including biotic stress. Early studies on the role of GSTs in plant biotic stress showed that certain GST genes are specifically up-regulated by microbial infections. Later numerous transcriptome-wide investigations proved that distinct groups of GSTs are markedly induced in the early phase of bacterial, fungal and viral infections. Proteomic investigations also confirmed the accumulation of multiple GST proteins in infected plants. Furthermore, functional studies revealed that overexpression or silencing of specific GSTs can markedly modify disease symptoms and also pathogen multiplication rates. However, very limited information is available about the exact metabolic functions of disease-induced GST isoenzymes and about their endogenous substrates. The already recognized roles of GSTs are the detoxification of toxic substances by their conjugation with glutathione, the attenuation of oxidative stress and the participation in hormone transport. Some GSTs display glutathione peroxidase activity and these GSTs can detoxify toxic lipid hydroperoxides that accumulate during infections. GSTs can also possess ligandin functions and participate in the intracellular transport of auxins. Notably, the expression of multiple GSTs is massively activated by salicylic acid and some GST enzymes were demonstrated to be receptor proteins of salicylic acid. Furthermore, induction of GST genes or elevated GST activities have often been observed in plants treated with beneficial microbes (bacteria and fungi) that induce a systemic resistance response (ISR) to subsequent pathogen infections. Further research is needed to reveal the exact metabolic functions of GST isoenzymes in infected plants and to understand their contribution to disease resistance.

Chloroplast Proteome of Nicotiana benthamiana Infected by Tomato Blistering Mosaic Virus

Tymovirus is a genus of plant pathogenic viruses that infects several dicotyledonous plants worldwide, causing serious diseases in economically important crops. The known cytopathic effect on the host cell organelles involves chloroplast membrane deformation and the induction of vesicles in its periphery. These vesicles are known to be the location where tymoviral genomic RNA replication occurs. Tomato blistering mosaic virus (ToBMV) is a tymovirus recently identified in tomato plants in Brazil, which is able to infect several other plants, including tobacco. In this work, we investigated the chloroplast proteomic profile of ToBMV-infected N. benthamiana using bidimensional electrophoresis (2-DE) and mass spectrometry, aiming to study the virus-host interaction related to the virus replication and infection. A total of approximately 200 spots were resolved, out of which 36 were differentially abundant. Differential spots were identified by mass spectrometry including photosynthesis-related and defense proteins. We identified proteins that may be targets of a direct interaction with viral proteins, such as ATP synthase β subunit, RNA polymerase beta-subunit, 50S ribosomal protein L6 and Trigger factor-like protein. The identification of these candidate proteins gives support for future protein-protein interaction studies to confirm their roles in virus replication and disease development.

Identification of differentially regulated maize proteins conditioning Sugarcane mosaic virus systemic infection

Sugarcane mosaic virus (SCMV) is the most important cause of maize dwarf mosaic disease. To identify maize genes responsive to SCMV infection and that may be involved in pathogenesis, a comparative proteomic analysis was performed using the first and second systemically infected leaves (termed 1 SL and 2 SL, respectively). Seventy-one differentially expressed proteins were identified in 1 SL and 2 SL upon SCMV infection. Among them, eight proteins showed the same changing patterns in both 1 SL and 2 SL. Functional annotations of regulated proteins and measurement of photosynthetic activity revealed that photosynthesis was more inhibited and defensive gene expression more pronounced in 1 SL than in 2 SL. Knockdown of regulated proteins in both 1 SL and 2 SL by a brome mosaic virus-based gene silencing vector in maize indicated that protein disulfide isomerase-like and phosphoglycerate kinase were required for optimal SCMV replication. By contrast, knockdown of polyamine oxidase (ZmPAO) significantly increased SCMV accumulation, implying that ZmPAO activity might contribute to resistance or tolerance. The results suggest that combining comparative proteomic analyses of different tissues and virus-induced gene silencing is an efficient way to identify host proteins supporting virus replication or enhancing resistance to virus infection.

Label-free Proteomic Reveals that Cowpea Severe Mosaic Virus Transiently Suppresses the Host Leaf Protein Accumulation During the Compatible Interaction with Cowpea (Vigna unguiculata [L.] Walp.)

Viruses are important plant pathogens that threaten diverse crops worldwide. Diseases caused by Cowpea severe mosaic virus (CPSMV) have drawn attention because of the serious damages they cause to economically important crops including cowpea. This work was undertaken to quantify and identify the responsive proteins of a susceptible cowpea genotype infected with CPSMV, in comparison with mock-inoculated controls, using label-free quantitative proteomics and databanks, aiming at providing insights on the molecular basis of this compatible interaction. Cowpea leaves were mock- or CPSMV-inoculated and 2 and 6 days later proteins were extracted and analyzed. More than 3000 proteins were identified (data available via ProteomeXchange, identifier PXD005025) and 75 and 55 of them differentially accumulated in response to CPSMV, at 2 and 6 DAI, respectively. At 2 DAI, 76% of the proteins decreased in amount and 24% increased. However, at 6 DAI, 100% of the identified proteins increased. Thus, CPSMV transiently suppresses the synthesis of proteins involved particularly in the redox homeostasis, protein synthesis, defense, stress, RNA/DNA metabolism, signaling, and other functions, allowing viral invasion and spread in cowpea tissues.

Chloroplast in Plant-Virus Interaction

In plants, the chloroplast is the organelle that conducts photosynthesis. It has been known that chloroplast is involved in virus infection of plants for approximate 70 years. Recently, the subject of chloroplast-virus interplay is getting more and more attention. In this article we discuss the different aspects of chloroplast-virus interaction into three sections: the effect of virus infection on the structure and function of chloroplast, the role of chloroplast in virus infection cycle, and the function of chloroplast in host defense against viruses. In particular, we focus on the characterization of chloroplast protein-viral protein interactions that underlie the interplay between chloroplast and virus. It can be summarized that chloroplast is a common target of plant viruses for viral pathogenesis or propagation; and conversely, chloroplast and its components also can play active roles in plant defense against viruses. Chloroplast photosynthesis-related genes/proteins (CPRGs/CPRPs) are suggested to play a central role during the complex chloroplast-virus interaction.

Molecular Variability and Distribution of Sugarcane Mosaic Virus in Shanxi, China

BACKGROUND

Sugarcane mosaic virus (SCMV) is responsible for large-scale economic losses in the global production of sugarcane, maize, sorghum, and some other graminaceous species. To understand the evolutionary mechanism of SCMV populations, this virus was studied in Shanxi, China. A total of 86 maize leaf samples (41 samples in 2012 and 45 samples in 2013) were collected from 4 regions of Shanxi.

RESULTS

Double-antibody sandwich (DAS)-ELISA and RT-PCR showed 59 samples (30 samples in 2012 and 29 samples in 2013) to be positive for SCMV, from which 10 new isolates of SCMV were isolated and sequenced. The complete genomes of these isolates are 9610 nt long, including the 5' and 3' non-coding regions, and encode a 3063-amino acid polyprotein. Phylogenetic analyses revealed that 24 SCMV isolates could be divided on the basis of the whole genome into 2 divergent evolutionary groups, which were associated with the host species. Among the populations, 15 potential recombination events were identified. The selection pressure on the genes of these SCMV isolates was also calculated. The results confirmed that all the genes were under negative selection.

CONCLUSIONS

Negative selection and recombination appear to be important evolutionary factors shaping the genetic structure of these SCMV isolates. SCMV is distributed widely in China and exists as numerous strains with distinct genetic diversity. Our findings will provide a foundation for evaluating the epidemiological characteristics of SCMV in China and will be useful in designing long-term, sustainable management strategies for SCMV.

Chloroplast in Plant-Virus Interaction

In plants, the chloroplast is the organelle that conducts photosynthesis. It has been known that chloroplast is involved in virus infection of plants for approximate 70 years. Recently, the subject of chloroplast-virus interplay is getting more and more attention. In this article we discuss the different aspects of chloroplast-virus interaction into three sections: the effect of virus infection on the structure and function of chloroplast, the role of chloroplast in virus infection cycle, and the function of chloroplast in host defense against viruses. In particular, we focus on the characterization of chloroplast protein-viral protein interactions that underlie the interplay between chloroplast and virus. It can be summarized that chloroplast is a common target of plant viruses for viral pathogenesis or propagation; and conversely, chloroplast and its components also can play active roles in plant defense against viruses. Chloroplast photosynthesis-related genes/proteins (CPRGs/CPRPs) are suggested to play a central role during the complex chloroplast-virus interaction.

Maize-Pathogen Interactions: An Ongoing Combat from a Proteomics Perspective

Maize (Zea mays L.) is a host to numerous pathogenic species that impose serious diseases to its ear and foliage, negatively affecting the yield and the quality of the maize crop. A considerable amount of research has been carried out to elucidate mechanisms of maize-pathogen interactions with a major goal to identify defense-associated proteins. In this review, we summarize interactions of maize with its agriculturally important pathogens that were assessed at the proteome level. Employing differential analyses, such as the comparison of pathogen-resistant and susceptible maize varieties, as well as changes in maize proteomes after pathogen challenge, numerous proteins were identified as possible candidates in maize resistance. We describe findings of various research groups that used mainly mass spectrometry-based, high through-put proteomic tools to investigate maize interactions with fungal pathogens Aspergillus flavus, Fusarium spp., and Curvularia lunata, and viral agents Rice Black-streaked Dwarf Virus and Sugarcane Mosaic Virus.

"Omics" of maize stress response for sustainable food production: opportunities and challenges

Maize originated in the highlands of Mexico approximately 8700 years ago and is one of the most commonly grown cereal crops worldwide, followed by wheat and rice. Abiotic stresses (primarily drought, salinity, and high and low temperatures), together with biotic stresses (primarily fungi, viruses, and pests), negatively affect maize growth, development, and eventually production. To understand the response of maize to abiotic and biotic stresses and its mechanism of stress tolerance, high-throughput omics approaches have been used in maize stress studies. Integrated omics approaches are crucial for dissecting the temporal and spatial system-level changes that occur in maize under various stresses. In this comprehensive analysis, we review the primary types of stresses that threaten sustainable maize production; underscore the recent advances in maize stress omics, especially proteomics; and discuss the opportunities, challenges, and future directions of maize stress omics, with a view to sustainable food production. The knowledge gained from studying maize stress omics is instrumental for improving maize to cope with various stresses and to meet the food demands of the exponentially growing global population. Omics systems science offers actionable potential solutions for sustainable food production, and we present maize as a notable case study.

Control of virus diseases in maize

Diseases caused by viruses are found throughout the maize-growing regions of the world and can cause significant losses for producers. In this review, virus diseases of maize and the pathogens that cause them are discussed. Factors leading to the spread of disease and measures for disease control are reviewed, as is our current knowledge of the genetics of virus resistance in this important crop.

Partially resistant Cucurbita pepo showed late onset of the Zucchini yellow mosaic virus infection due to rapid activation of defense mechanisms as compared to susceptible cultivar

Zucchini yellow mosaic virus (ZYMV) is an emerging viral pathogen in cucurbit-growing areas wordwide. Infection causes significant yield losses in several species of the family Cucurbitaceae. To identify proteins potentially involved with resistance toward infection by the severe ZYMV-H isolate, two Cucurbita pepo cultivars (Zelena susceptible and Jaguar partially resistant) were analyzed using a two-dimensional gel electrophoresis-based proteomic approach. Initial symptoms on leaves (clearing veins) developed 6-7 days post-inoculation (dpi) in the susceptible C. pepo cv. Zelena. In contrast, similar symptoms appeared on the leaves of partially resistant C. pepo cv. Jaguar only after 15 dpi. This finding was confirmed by immune-blot analysis which showed higher levels of viral proteins at 6 dpi in the susceptible cultivar. Leaf proteome analyses revealed 28 and 31 spots differentially abundant between cultivars at 6 and 15 dpi, respectively. The variance early in infection can be attributed to a rapid activation of proteins involved with redox homeostasis in the partially resistant cultivar. Changes in the proteome of the susceptible cultivar are related to the cytoskeleton and photosynthesis.

Molecular biology of potyviruses

Potyvirus is the largest genus of plant viruses causing significant losses in a wide range of crops. Potyviruses are aphid transmitted in a nonpersistent manner and some of them are also seed transmitted. As important pathogens, potyviruses are much more studied than other plant viruses belonging to other genera and their study covers many aspects of plant virology, such as functional characterization of viral proteins, molecular interaction with hosts and vectors, structure, taxonomy, evolution, epidemiology, and diagnosis. Biotechnological applications of potyviruses are also being explored. During this last decade, substantial advances have been made in the understanding of the molecular biology of these viruses and the functions of their various proteins. After a general presentation on the family Potyviridae and the potyviral proteins, we present an update of the knowledge on potyvirus multiplication, movement, and transmission and on potyvirus/plant compatible interactions including pathogenicity and symptom determinants. We end the review providing information on biotechnological applications of potyviruses.

Analysis of Clonostachys rosea-induced resistance to tomato gray mold disease in tomato leaves

Tomato gray mold disease, caused by Botrytis cinerea, is a serious disease in tomato. Clonostachys rosea is an antagonistic microorganism to B. cinerea. To investigate the induced resistance mechanism of C. rosea, we examined the effects of these microorganisms on tomato leaves, along with changes in the activities of three defense enzymes (PAL, PPO, GST), second messengers (NO, H2O2, O2(-)) and phytohormones (IAA, ABA, GA3, ZT, MeJA, SA and C2H4). Compared to the control, all treatments induced higher levels of PAL, PPO and GST activity in tomato leaves and increased NO, SA and GA3 levels. The expression of WRKY and MAPK, two important transcription factors in plant disease resistance, was upregulated in C. rosea- and C. rosea plus B. cinerea-treated samples. Two-dimensional gel electrophoresis analysis showed that two abundant proteins were present in the C. rosea plus B. cinerea-treated samples but not in the other samples. These proteins were determined (by mass spectrum analysis) to be LEXYL2 (β-xylosidase) and ATP synthase CF1 alpha subunit. Therefore, C. rosea plus B. cinerea treatment induces gray mold resistance in tomato. This study provides a basis for elucidating the mechanism of C. rosea as a biocontrol agent.