Mungbean Yellow Mosaic India Virus Infection Research Articles

Identification of mungbean yellow mosaic India virus and susceptibility-related metabolites in the apoplast of mung bean leaves.

The investigation of MYMIV-infected mung bean leaf apoplast revealed viral genome presence, increased EVs secretion, and altered stress-related metabolite composition, providing comprehensive insights into plant-virus interactions. The apoplast, an extracellular space around plant cells, plays a vital role in plant-microbe interactions, influencing signaling, defense, and nutrient transport. While the involvement of apoplast and extracellular vesicles (EVs) in RNA virus infection is documented, the role of the apoplast in plant DNA viruses remains unclear. This study explores the apoplast's role in mungbean yellow mosaic India virus (MYMIV) infection. Our findings demonstrate the presence of MYMIV genomic components in apoplastic fluid, suggesting potential begomovirus cell-to-cell movement via the apoplast. Moreover, MYMIV infection induces increased EVs secretion into the apoplast. NMR-based metabolomics reveals altered metabolic profiles in both apoplast and symplast in response to MYMIV infection, highlighting key metabolites associated with stress and defense mechanisms. The data show an elevation of α- and β-glucose in both apoplast and symplast, suggesting a shift in glucose utilization. Interestingly, this increase in glucose does not contribute to the synthesis of phenolic compounds, potentially influencing the susceptibility of mung bean to MYMIV. Fructose levels increase in the symplast, while apoplastic sucrose levels rise significantly. Symplastic aspartate levels increase, while proline exhibits elevated concentration in the apoplast and reduced concentration in the cytosol, suggesting a role in triggering a hypersensitive response. These findings underscore the critical role of the apoplast in begomovirus infection, providing insights for targeted viral disease management strategies.

NMR-Based Metabolomic Profiling of Mungbean Infected with Mungbean Yellow Mosaic India Virus.

Mungbean is an important legume mainly cultivated in Southeast Asia known for cheap source of food protein. Yellow mosaic disease (YMD) of mungbean is one of the most damaging diseases caused by mungbean yellow mosaic virus (MYMV) and mungbean yellow mosaic India virus (MYMIV) in India. The genetic basis of YMD resistance of mungbean is not well studied yet. Our present studies aimed to explore the genetic basis of YMD resistance through molecular, biochemical and metabolomics approach. Molecular analysis of YMV-infected mungbean plant materials revealed the presence of MYMIV. Chlorophyll contents were estimated as mosaic symptoms that cause chlorosis and necrosis in infected leaves. Chlorophyll a, b and total chlorophyll content were significantly reduced by 27-55% in infected samples compared non-infected control samples. 1H NMR-based metabolomic profiling of virus-infected mungbean were carried out, and we found that vital changes occurred during the development of MYMIV infection in mungbean. A total of fifty metabolites were identified in mungbean leaf samples. Principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA) separated the severely infected sample from the non-infected samples. Orthogonal partial least discrimination analysis (OPLS-DA) revealed significant differences in MYMIV-infected and non-infected control samples. The featured metabolites in MYMIV infected and control samples were amino acids, carbohydrates, and organic acids. Relative abundance of sucrose, γ-amino butyric acid (GABA), proline, alanine, phenylalanine, tryptophan, pyruvate, ascorbate, and citrates were found as differential metabolites. Our results suggest that metabolic changes in infected mungbean samples is related to the viral acquisition. The present study may help in better understanding the metabolic alterations during biotic stress in mungbean.

Biochemical alterations in soybean (Glycine max) infected with Mungbean yellow mosaic India virus in Lalitpur dist., Bundelkhand region of India

The yellow mosaic symptoms on soybean (Glycine max) were observed at various sites in the Bundelkhand region of India and infection of begomovirus was detected through PCR. The begomovirus isolates were identified as Mungbean yellow mosaic India virus (MYMIV). MYMIV infection in soybean results in the production of reactive oxygen species to activate defense mechanisms at different levels to overcome the damage caused in the severely infected crops. The biomarkers of stress in plants such as, hydrogen peroxide (H2O2), catalase (CAT), Superoxide dismutase (SOD), Ascorbate peroxidase (APX) contents studies also suggested elevation in stress-related enzymes and also a significant reduction in sugar, chlorophyll, and protein contents have been observed. Previously alteration in biochemical due biotic and abiotic stresses have been reported in different varieties of legumes, but biochemical alterations in soybean infected by MYMIV are being reported for the first time from the Bundelkhand region of India.

Construction of Full-length Dimer Clones of Yellow Mosaic Virus and Screening of Blackgram Germplasm using Agroinoculation

Background: Vigna mungo (Blackgram) is the major pulse crop cultivated in the Indian sub-continent. It is highly prone to yellow mosaic disease (YMD), which is widespread problem because all cultivated varieties are susceptible to the YMD in Andhra Pradesh state. The presence of two species of begomovirus i.e. Mungbean yellow mosaic virus (MYMV) and Mungbean yellow mosaic India virus (MYMIV) with YMD was reported in Andhra Pradesh. The current study was aimed to develop simple method of viral dimer clone construction and identifying the resistant blackgram genotypes against two species of begomovirus (MYMV and MYMIV) by agroinoculation technique. Methods: In this study, we standardize the rolling circle amplification (RCA) based viral dimer clone construction (MYMV DNA-A, MYMV DNA-B and MYMIV DNA-A) and constructed viral dimer clones were used to transform Agrobacterium tumefaciens EHA105 cells through freeze-thaw technique. Sprouted seed method of agroinoculation screening was conducted. Result: Total 45 blackgram genotypes were screened by sprouted seed method of agroinoculation with two combinations of viral dimeric constructs (MYMV-TPT-A+MYMV-TPT-B and MYMIV-TPT-A+MYMV-TPT-B). Twenty four genotypes offered resistant against MYMV infection and twenty three genotypes were resistant to MYMIV infection. Total 17 genotypes offered resistance to both species of virus (MYMV andMYMIV) associated with YMD.

Biochemical Alterations in the Leaves of Resistant and Susceptible Mungbean Genotypes Infected with Mungbean Yellow Mosaic India Virus

Mungbean (Vigna radiata), an important leguminous crop, is highly susceptible to yellow mosaic disease (YMD) caused by Mungbean yellow mosaic India virus (MYMIV), resulting in high yield penalty. Previously, different varieties of mungbean have been reported possessing resistance/ tolerance against MYMIV. However, the molecular events occurring during compatible and incompatible interactions between mungbean and MYMIV are yet to be explored. Therefore, in this study using MYMIV-resistant (NM-2016), moderately resistant (NM-2011) and susceptible genotype (VC-1647C), alterations in various biochemical attributes due to MYMIV infection were analysed and compared with healthy non-inoculated control plants for understanding the resistance mechanism. After MYMIV inoculation, the level of total phenolic contents (TPC) and total soluble proteins (TSP) increased significantly in the susceptible genotype. However, the level of Malondialdehyde (MDA) and Ascorbate peroxidase (APX) remained same in all the genotypes. Level of superoxide dismutase (SOD) and catalase (CAT) decreased in the susceptible genotype but CAT level increased in the moderately resistant genotype. Protease level decreased significantly in all the genotypes while esterase level increased in moderately resistant and susceptible genotype. Peroxidase (POD) increased only in moderately resistant genotype and Total Oxidant Status (TOS) increased significantly in the susceptible genotype. Due to MYMIV infection the level of all plant pigments decreased in all the genotypes tested. The comparative proteome analysis using SDS-PAGE resolved 22 peptides with molecular weight from 12.5 to 163 kDa. Differential expression of protein phosphatase 2C (PP2C) and Cytochrome b6 (Photosynthesis) in resistant and moderately resistant genotypes; Pectin acetyl esterase and Resistant specific protein-1(4) in resistant genotype and up-regulation of superoxide dismutase [Cu-Zn] and RuBisco by MYMIV may have triggered signal transduction pathway and consequently induced a resistance response against MYMIV in V. radiata by activating PR proteins.

Differential responses of Phaseolus vulgaris cultivars following mungbean yellow mosaic India virus infection.

Phaseolus vulgaris, commonly known as French bean is a vital leguminous crop worldwide and India stood 1st rank in dry bean and 4th rank in green bean production worldwide (FAOSTAT 2017). However, this production is severely affected by Mungbean yellow mosaic India virus (MYMIV) infection. Hence it is very important to identify MYMIV tolerant P. vulgaris cultivars. MYMIV infection results in the production of reactive oxygen species and plant cells have evolved complex defense mechanisms at different levels to overcome the damage. Our study for the first time focused on the changes at the morphological and biochemical level, as well as on the relative quantification of MYMIV genes in nine cultivars of P. vulgaris after MYMIV infection. Highest growth and the highest accumulation of four antioxidants of cv. 'Anupam' after MYMIV infection, established that cv. 'Anupam' was less affected by MYMIV infection amongst all nine cultivars. Relative quantification studies also correlated well with these results. Additionally, there is a consistent level of photosynthetic pigments content in mock- and MYMIV-treated seedlings of cv. 'Anupam' over early infection period. Combining all the results we conclude that cv. 'Anupam' is a MYMIV tolerant cultivar.

Comparative transcriptome profiling of a resistant vs. susceptible Vigna mungo cultivar in response to Mungbean yellow mosaic India virus infection reveals new insight into MYMIV resistance

Mungbean yellow mosaic India virus (MYMIV), causal agent of the yellow mosaic disease (YMD) in leguminous crops, causes enormous fall in productivity of economically important legumes worldwide. Vigna mungo is severely affected by YMD. In this study, the transcriptional modifications in V. mungo during MYMIV resistance as well as susceptibility were studied and 145 and 109 differentially expressed transcripts were identified in resistant and susceptible plants, respectively through suppression subtractive hybridization. Selected transcripts were validated through RT-qPCR. In incompatible interaction, significant induced expression of genes present in jasmonic acid signalling pathway was observed. Moreover, in incompatible interaction the generation of physical barrier upon virus invasion and maintenance of reactive oxygen species homeostasis was also evidenced. In compatible interaction, the virus succeeded to manipulate the host machinery resulting in significant decrease in defense related gene expression leading to manifestation of disease symptoms. We have generated two hypothetical models of incompatible and compatible interactions based on the possible biological and molecular function of differentially expressed transcripts obtained from resistant and susceptible plants following MYMIV infection. Knowledge gained from these models will help in deciphering the mechanism of MYMIV resistance not only in V. mungo but also in other plant-pathogen interaction study.

Exogenous application of methyl jasmonate induces defense response and develops tolerance against mungbean yellow mosaic India virus in Vigna mungo.

Vigna mungo (L.)Hepper is an economically important leguminous crop in south-east Asia. However, its production is severely affected by Mungbean yellow mosaic India virus (MYMIV). It is well established that methyl jasmonate (MeJA) is effective in inducing resistance against pathogens in several plants. To assess the role of MeJA in developing MYMIV tolerance in V. mungo, we analysed time-dependent biochemical and molecular responses of MYMIV susceptible V. mungo after exogenous application of different MeJA concentrations, followed by MYMIV infection. Our analysis revealed that exogenous application of different concentrations of MeJA resulted in decreased levels of malondialdehyde with higher membrane stability index values in MYMIV susceptible V. mungo, suggesting the protective role of MeJA through restoring the membrane stability. Moreover, the level of expression of different antioxidative enzymes revealed that exogenous MeJA is also very effective in ROS homeostasis maintenance. Enhanced expressions of the defence marker genes lipoxygenase and phenylalanine ammonia-lyase and the reduced expression of the MYMIV coat-protein encoding gene in all MeJA treated plants post MYMIV infection revealed that exogenous application of MeJA is effective for MYMIV tolerance in V. mungo. Our findings provide new insights into the physiological and molecular mechanisms of MYMIV tolerance in Vigna induced by MeJA.

Identification and characterization of differentially expressed Phaseolus vulgaris miRNAs and their targets during mungbean yellow mosaic India virus infection reveals new insight into Phaseolus-MYMIV interaction

Phaseolus vulgaris is an economically important legume in tropical and subtropical regions of Asia, Africa, Latin-America and parts of USA and Europe. However, its production gets severely affected by mungbean yellow mosaic India virus (MYMIV). We aim to identify and characterize differentially expressed miRNAs during MYMIV-infection in P. vulgaris. A total of 422 miRNAs are identified of which 292 are expressed in both MYMIV-treated and mock-treated samples, 109 are expressed only in MYMIV-treated and 21 are expressed only in mock-treated samples. Selected up- and down-regulated miRNAs are validated by RT-qPCR. 3367 target ORFs are identified for 270 miRNAs. Selected targets are validated by 5′ RLM-RACE. Differentially expressed miRNAs regulate transcription factors and are involved in improving stress tolerance to MYMIV. These findings will provide an insight into the role of miRNAs during MYMIV infection in P. vulgaris in particular and during any biotic stress conditions in Leguminosae family in general.

Mapping of Duplicate Dominant Genes for Mungbean yellow mosaic India virus Resistance in Glycine soja

Glycine soja Siebold & Zucc. PI 393551 carries gene(s) for resistance to yellow mosaic disease, which is caused by Mungbean yellow mosaic India virus (MYMIV). Yellow mosaic disease is a serious constraint to soybean [Glycine max (L.) Merr.] production in India. However, the gene(s) imparting resistance to MYMIV in G. soja have not yet been mapped. In the present study, three F2 populations derived from crosses of the three G. max cultivars ‘Ankur’, ‘Sawarn Vasundhra’, and ‘JS335’ with PI 393551, the donor for MYMIV resistance, were phenotyped for reaction to MYMIV at the geographic hot spot for yellow mosaic disease to determine inheritance of MYMIV resistance in PI 393551. All three F2 populations exhibited a 15:1 ratio of individuals resistant and susceptible to MYMIV, indicating duplicate dominant inheritance of MYMIV resistance genes. Further, a large F2 population (1520 plants) reconstructed from JS335 × PI 393551 was used for mapping MYMIV resistance genes. Bulked segregant analysis identified two genomic regions associated with MYMIV resistance, one on chromosome 8, and another on chromosome 14. A total of 78 plants with 100% MYMIV infection, which were expected to be homozygous for recessive genes, were genotyped using polymorphic simple sequence repeat (SSR) markers near linked markers on chromosome 8 and 14. Genetic analyses revealed tight linkages of MYMIV resistance with SSR marker BARCSOYSSR_08_0867 (15,434,295 bp) on chromosome 8, and with BARCSOYSSR_14_1416 (47,686,933 bp) and BARCSOYSSR_14_1417 (47,738,940 bp) on chromosome 14. The identified SSR markers that are tightly linked to MYMIV resistance genes will be useful for introgression of MYMIV resistance from G. soja into G. max.

Molecular and biochemical characterization of mungbean yellow mosaic India virus resistance in leguminous host Vigna mungo

Mungbean yellow mosaic India virus (MYMIV)—the causal agent of the yellow mosaic disease is responsible for severe damage of crops that are of great economic importance. In the current study, we explored the process of MYMIV infection and its natural resistance by analysing the expression of early and late viral genes at different time points in the leaves of resistant and susceptible Vigna mungo plants. Accordingly, we have periodically evaluated several biochemical parameters commonly associated with oxidative status of resistant and susceptible V. mungo plants during MYMIV infection. Our study revealed that accumulation levels of the early as well as late expressed genes of MYMIV were low and high in the resistant and susceptible plants, respectively; whereas membrane stability index (MSI) exhibited an opposite response. Moreover, a decrease in the malondialdehyde levels along with an increase in the activities/levels of different antioxidant enzymes, total phenol and H2O2 was noted during the early stages of infection in the resistant plants. Such observations argue in favour of strong defensive capability of the resistant plants in restricting the accumulation of viral RNA and generation of harmful free radicals within the studied tissue. Collectively, it appears that obstruction of viral invasion in plant cell wall, restriction in viral DNA replication, and early onset of antioxidant defense responses altogether might be responsible for MYMIV natural resistance. Such information is helpful in understanding the pathogenesis of MYMIV infection and its resistance in V. mungo and other economically important crops.

RNAi-derived transgenic resistance to Mungbean yellow mosaic India virus in cowpea.

Cowpea is an important grain legume crop of Africa, Latin America, and Southeast Asia. Leaf curl and golden mosaic diseases caused by Mungbean yellow mosaic India virus (MYMIV) have emerged as most devastating viral diseases of cowpea in Southeast Asia. In this study, we employed RNA interference (RNAi) strategy to control cowpea-infecting MYMIV. For this, we generated transgenic cowpea plants harbouring three different intron hairpin RNAi constructs, containing the AC2, AC4 and fusion of AC2 and AC4 (AC2+AC4) of seven cowpea-infecting begomoviruses. The T0 and T1 transgenic cowpea lines of all the three constructs accumulated transgene-specific siRNAs. Transgenic plants were further assayed up to T1 generations, for resistance to MYMIV using agro-infectious clones. Nearly 100% resistance against MYMIV infection was observed in transgenic lines, expressing AC2-hp and AC2+AC4-hp RNA, when compared with untransformed controls and plants transformed with empty vectors, which developed severe viral disease symptoms within 3 weeks. The AC4-hp RNA expressing lines displayed appearance of milder symptoms after 5 weeks of MYMIV-inoculation. Northern blots revealed a positive correlation between the level of transgene-specific siRNAs accumulation and virus resistance. The MYMIV-resistant transgenic lines accumulated nearly zero or very low titres of viral DNA. The transgenic cowpea plants had normal phenotype with no yield penalty in greenhouse conditions. This is the first demonstration of RNAi-derived resistance to MYMIV in cowpea.

Molecular and biochemical characterization of a Vigna mungo MAP kinase associated with Mungbean Yellow Mosaic India Virus infection and deciphering its role in restricting the virus multiplication

Yellow Mosaic Disease caused by the begomovirus Mungbean Yellow Mosaic India Virus (MYMIV) severely affects many economically important legumes. Recent investigations in Vigna mungo – MYMIV incompatible interaction identified a MAPK homolog in the defense signaling pathway. An important branch of immunity involves phosphorylation by evolutionary conserved Mitogen-activated protein kinases (MAPK) that transduce signals of pathogen invasion to downstream molecules leading to diverse immune responses. However, most of the knowledge of MAPKs is derived from model crops, and functions of these versatile kinases are little explored in legumes. Here we report characterization of a MAP kinase (VmMAPK1), which was induced upon MYMIV-inoculation in resistant V. mungo. Phylogenetic analysis revealed that VmMAPK1 is closely related to other plant-stress-responsive MAPKs. Both mRNA and protein of VmMAPK1 were accumulated upon MYMIV infection. The VmMAPK1 protein localized in the nucleus as well as cytoplasm and possessed phosphorylation activity in vitro. A detailed biochemical characterization of purified recombinant VmMAPK1 demonstrated an intramolecular mechanism of autophosphorylation and self-catalyzed phosphate incorporation on both threonine and tyrosine residues. The Vmax and Km values of recombinant VmMAPK1 for ATP were 6.292nmol/mg/min and 0.7978μM, respectively. Furthermore, the ability of VmMAPK1 to restrict MYMIV multiplication was validated by its ectopic expression in transgenic tobacco. Importantly, overexpression of VmMAPK1 resulted in the considerable upregulation of defense-responsive marker PR genes. Thus, the present data suggests the critical role of VmMAPK1 in suppressing MYMIV multiplication presumably through SA-mediated signaling pathway and inducing PR genes establishing the significant implications in understanding MAP kinase gene function during Vigna-MYMIV interaction; and hence paves the way for introgression of resistance in leguminous crops susceptible to MYMIV.

Expression dynamics of Glycine max (L.) Merrill microRNAs (miRNAs) and their targets during Mungbean yellow mosaic India virus (MYMIV) infection

MicroRNAs (miRNAs) are class of small non coding RNAs (sncRNAs) that modulate gene regulatory mechanisms including conferring antiviral resistance in plants. Expressional changes of selected conserved miRNAs and putatively antiviral miRNAs were analyzed in two soybean genotypes (JS335 and UPSM534) with contrasting disease reaction trait against Mungbean yellow mosaic India virus (MYMIV) family Geminiviridae. Expression profiling of conserved miRNAs and corresponding target mRNAs in both the soybean genotypes suggests the role of Argonaute homeostasis in virus resistance along with the gene regulatory changes in hormonal signaling pathways. Putative antiviral miRNAs displayed upregulation upon MYMIV infection in both the soybean genotypes. Further, experimental evidence prove that soybean derived miRNA potentially target and direct cleavage of MYMIV mRNA encoding movement protein (BC1). Thus, this work provides molecular insights regarding changes in expression of miRNAs during MYMIV infection and improves deeper understanding of role of soybean miRNAs in MYMIV resistance. To the best of our knowledge this is the first report of soybean derived miRNAs exhibiting potential antiviral resistance during begomovirus infection.

The AC5 protein encoded by Mungbean yellow mosaic India virus is a pathogenicity determinant that suppresses RNA silencing-based antiviral defenses.

It is generally accepted that begomoviruses in the family Geminiviridae encode four proteins (from AC1/C1 to AC4/C4) using the complementary-sense DNA as template. Although AC5/C5 coding sequences are increasingly annotated in databases for many begomoviruses, the evolutionary relationships and functions of this putative protein in viral infection are obscure. Here, we demonstrate several important functions of the AC5 protein of a bipartite begomovirus, Mungbean yellow mosaic India virus (MYMIV). Mutational analyses and transgenic expression showed that AC5 plays a critical role in MYMIV infection. Ectopic expression of AC5 from a Potato virus X (PVX) vector resulted in severe mosaic symptoms followed by a hypersensitive-like response in Nicotiana benthamiana. Furthermore, MYMIV AC5 effectively suppressed post-transcriptional gene silencing induced by single-stranded but not double-stranded RNA. AC5 was also able to reverse transcriptional gene silencing of a green fluorescent protein transgene by reducing methylation of promoter sequences, probably through repressing expression of a CHH cytosine methyltransferase (DOMAINS REARRANGED METHYLTRANSFERASE2) in N.benthamiana. Our results demonstrate that MYMIV AC5 is a pathogenicity determinant and a potent RNA silencing suppressor that employs novel mechanisms to suppress antiviral defenses, and suggest that the AC5 function may be conserved among many begomoviruses.

Differential soybean gene expression during early phase of infection with Mungbean yellow mosaic India virus.

Mungbean yellow mosaic India virus (MYMIV), a bipartite begomovirus, causes yellow mosaic disease to soybean. Studies related to host gene expression in response to begomovirus infection have mostly been performed with systemically infected tissues at a later period of infection. In this study, soybean gene expression analysis has been performed to understand local responses against MYMIV at an early stage of infection before appearance of detectable limit of late viral transcripts. 444 soybean transcripts belonging to eleven functional categories showed significant changes in expression level at two days after infection. MYMIV infection resulted in enhanced expression of genes associated with hypersensitive response, programmed cell death and resistance response pathways and reduced expression of genes for photosynthesis and sugar transport. Comparative expression analysis of selected transcripts in the susceptible and a resistant variety displayed differential expression of host genes involved in intercellular virus movement and long distance signaling of systemic acquired resistance.

Spectral reflectance pattern in soybean for assessing yellow mosaic disease.

Remote sensing technique is useful for monitoring large crop area at a single time point, which is otherwise not possible by visual observation alone. Yellow mosaic disease (YMD) is a serious constraint in soybean production in India. However, hardly any basic information is available for monitoring YMD by remote sensing. Present study examines spectral reflectance of soybean leaves due to Mungbean yellow mosaic India virus (MYMIV) infection in order to identify YMD sensitive spectral ratio or reflectance. Spectral reflectance measurement indicated significant (p<0.001) change in reflectance in the infected soybean canopy as compared to the healthy one. In the infected canopy, reflectance increased in visible region and decreased in near infra-red region of spectrum. Reflectance sensitivity analysis indicated wavelength ~642, ~686 and ~750nm were sensitive to YMD infection. Whereas, in yellow leaves induced due to nitrogen deficiency, the sensitive wavelength was ~589nm. Due to viral infection, a shift occurred in red and infra-red slope (called red edge) on the left in comparison to healthy one. Red edge shift was a good indicator to discriminate yellow mosaic as chlorophyll gets degraded due to MYMIV infection. Correlation of reflectance at 688nm (R688) and spectral reflectance ratio at 750 and 445nm (R750/R445) with the weighted mosaic index indicated that detection of yellow mosaic is possible based on these sensitive bands. Our study for the first time identifies the yellow mosaic sensitive band as R688 and R750/R445, which could be utilized to scan satellite data for monitoring YMD affected soybean cropping regions.

Proteomics approach combined with biochemical attributes to elucidate compatible and incompatible plant-virus interactions between Vigna mungo and Mungbean Yellow Mosaic India Virus

BackgroundVigna mungo, a tropical leguminous plant, highly susceptible to yellow mosaic disease caused by Mungbean Yellow Mosaic India Virus (MYMIV) resulting in high yield penalty. The molecular events occurring during compatible and incompatible interactions between V. mungo and MYMIV pathosystem are yet to be explored. In this study biochemical analyses in conjunction with proteomics of MYMIV-susceptible and -resistant V. mungo genotypes were executed to get an insight in the molecular events during compatible and incompatible plant-virus interactions.ResultsBiochemical analysis revealed an increase in phenolics, hydrogen peroxide and carbohydrate contents in both compatible and incompatible interactions; but the magnitudes were higher during incompatible interaction. In the resistant genotype the activities of superoxide dismutase and ascorbate peroxidase increased significantly, while catalase activity decreased. Comparative proteome analyses using two-dimensional gel electrophoresis coupled with mass spectrometry identified 109 differentially abundant proteins at 3, 7 and 14 days post MYMIV-inoculation. Proteins of several functional categories were differentially changed in abundance during both compatible and incompatible interactions. Among these, photosynthesis related proteins were mostly affected in the susceptible genotype resulting in reduced photosynthesis rate under MYMIV-stress. Differential intensities of chlorophyll fluorescence and chlorophyll contents are in congruence with proteomics data. It was revealed that Photosystem II electron transports are the primary targets of MYMIV during pathogenesis. Quantitative real time PCR analyses of selected genes corroborates with respective protein abundance during incompatible interaction. The network of various cellular pathways that are involved in inducing defense response contains several conglomerated cores of nodal proteins, of which ascorbate peroxidase, rubisco activase and serine/glycine hydroxymethyl transferase are the three major hubs with high connectivity. These nodal proteins play the crucial role of key regulators in bringing about a coordinated defense response in highly orchestrated manner.ConclusionsBiochemical and proteomic analyses revealed early accumulation of the defense/stress related proteins involved in ROS metabolism during incompatible interaction. The robustness in induction of defense/stress and signal transduction related proteins is the key factor in inducing resistance. The mechanism of MYMIV-resistance in V. mungo involves redirection of carbohydrate flux towards pentose phosphate pathway. Some of these identified, differentially regulated proteins are also conferring abiotic stress responses illustrating harmony amongst different stress responses. To the best of our knowledge, this is the lone study deciphering differential regulations of V. mungo leaf proteome upon MYMIV infection elucidating the mode of resistance response at the biochemical level.

Isolation, Characterization, and Structure Analysis of a Non-TIR-NBS-LRR Encoding Candidate Gene from MYMIV-Resistant Vigna mungo

Yellow mosaic disease of Vigna mungo caused by Mungbean yellow mosaic India virus (MYMIV) is still a major threat in the crop production. A candidate disease resistance (R) gene, CYR1 that co-segregates with MYMIV-resistant populations of V. mungo has been isolated. CYR1 coded in silico translated protein sequence comprised of 1,176 amino acids with coiled coil structure at the N-terminus, central nucleotide binding site (NBS) and C-terminal leucine-rich repeats (LRR) that belongs to non-TIR-NBS-LRR subfamily of plant R genes. CYR1 transcript was unambiguously expressed during incompatible plant virus interactions. A putative promoter-like sequence present upstream of this candidate gene perhaps regulates its expression. Enhanced transcript level upon MYMIV infection suggests involvement of this candidate gene in conferring resistance against the virus. In silico constructed 3D models of NBS and LRR regions of this candidate protein and MYMIV-coat protein (CP) revealed that CYR1-LRR forms an active pocket and successively interacts with MYMIV-CP during docking, like that of receptor-ligand interaction; indicating a critical role of CYR1 as signalling molecule to protect V. mungo plants from MYMIV. This suggests involvement of CYR1 in recognizing MYMIV-effector molecule thus contributing to incompatible interaction. This study is the first stride to understand molecular mechanism of MYMIV resistance.

Diagnosis of Symptomless Yellow mosaic begomovirus Infection in Pigeonpea by Using Cloned Mungbean yellow mosaic India virus as Probe

One isolate of Mungbean yellow mosaic India virus (MYMIV) of mungbean plants from Sri Ganganagar, Rajasthan, designated as MYMIV-Mg was isolated and DNA-A and DNA-B, the two full length bipartite genomic components of this virus, were cloned. The [α-32P] labeled diagnostic probes specific to these cloned DNA-A and -B of MYMIV-Mg were used to detect the virus infection in infected plants by nucleic acid spot hybridization (NASH) test. The NASH tests detected the MYMIV infection and concentration of viral titre in susceptible, moderately susceptible, resistant and symptomless genotypes of pigeonpea (Cajanus cajan) plants. Fourteen genotypes of pigeonpea were tested against five naturally occurring MYMIV variants viz.,.MYMIV Bg, -MgD, -MoL, -Mg and -Pp1 through viruliferous whitefly (Bemisia tabaci) transmission in greenhouse condition. Disease incidence and severity of MYMIV in different pigeonpea genotypes varied with the variants of MYMIV. Many genotypes of pigeonpea did not produce visible yellow mosaic symptoms after inoculation with MYMIV variants MYMIV-Bg, -MbD and -MoL, although, majority of the symptomless genotypes were found to be infected by MYMIV, as viral DNA was detected by NASH test.