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Extra-large G-proteins influence plant response to Sclerotinia sclerotiorum by regulating glucosinolate metabolism in Brassica juncea.

ABSTRACT: Heterotrimeric G-proteins are one of the highly conserved signal transducers across phyla. Despite the obvious importance of G-proteins in controlling various plant growth and environmental responses, there is no information describing the regulatory complexity of G-protein networks during pathogen response in a polyploid crop. Here, we investigated the role of extra-large G-proteins (XLGs) in the oilseed crop Brassica juncea, which has inherent susceptibility to the necrotrophic fungal pathogen Sclerotinia sclerotiorum. The allotetraploid B. juncea genome contains multiple homologs of three XLG genes (two BjuXLG1, five BjuXLG2, and three BjuXLG3), sharing a high level of sequence identity, gene structure organization, and phylogenetic relationship with the progenitors' orthologs. Quantitative reverse transcription PCR analysis revealed that BjuXLGs have retained distinct expression patterns across plant developmental stages and on S. sclerotiorum infection. To determine the role of BjuXLG genes in the B. juncea defence response against S. sclerotiorum, RNAi-based suppression was performed. Disease progression analysis showed more rapid lesion expansion and fungal accumulation in BjuXLG-RNAi lines compared to the vector control plants, wherein suppression of BjuXLG3 homologs displayed more compromised defence response at the later time point. Knocking down BjuXLGs caused impairment of the host resistance mechanism to S. sclerotiorum, as indicated by reduced expression of defence marker genes PDF1.2 and WRKY33 on pathogen infection. Furthermore, BjuXLG-RNAi lines showed reduced accumulation of leaf glucosinolates on S. sclerotiorum infection, wherein aliphatic glucosinolates were significantly compromised. Overall, our data suggest that B. juncea XLG genes are important signalling nodes modulating the host defence pathways in response to this necrotrophic pathogen.

SUBMITTER: Tiwari R

PROVIDER: S-EPMC8435238 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:White mold disease, caused by the necrotrophic fungus Sclerotinia sclerotiorum, affects Brassica crops. Brassica crops produce a broad array of compounds, such as glucosinolates, which contribute to the defense against pathogens. From their hydrolysis, several products arise that have antimicrobial activity (GHPs) whose toxicity is structure dependent. S. sclerotiorum may overcome the toxic effect of moderate GHP concentrations after prolonged exposure to their action. Our objective was to identify the molecular mechanism underlying S. sclerotiorum response to long exposure to two chemically diverse GHPs: aliphatic GHP allyl-isothiocyanate (AITC) and indole GHP indol-3-carbinol (I3C). We found that the transcriptomic response is dependent on the type of GHP and on their initial target, involving cell membranes in the case of AITC or DNA in the case of I3C. Response mechanisms include the reorganization of chromatin, mediated by histone chaperones hip4 and cia1, ribosome synthesis controlled by the kinase-phosphatase pair aps1-ppn1, catabolism of proteins, ergosterol synthesis, and induction of detoxification systems. These mechanisms probably help S. sclerotiorum to grow and survive in an environment where GHPs are constantly produced by Brassica plants upon glucosinolate breakdown. IMPORTANCEBrassica species, including important vegetable crops, such as cabbage, cauliflower, or broccoli, or oil crops, such as rapeseed, produce specific chemical compounds useful to protect them against pests and pathogens. One of the most destructive Brassica diseases in temperate areas around the world is Sclerotinia stem rot, caused by the fungus Sclerotinia sclerotiorum. This is a generalist pathogen that causes disease over more than 400 plant species, being a serious threat to economically important crops worldwide, including potato, bean, soybean, and sunflower, among many others. Understanding the mechanisms utilized by pathogens to overcome specific plant defensive compounds can be useful to increase plant resistance. Our study demonstrated that Sclerotinia shows different adaptation mechanisms, including detoxification systems, to grow and survive when plant protective compounds are present.

Project description:White mold or stem rot disease are ubiquitously distributed throughout the world and the causal organism of this disease Sclerotinia sclerotiorum (Lib.) de Bary, is known to infect over 400 plant species. Sclerotinia stem rot is one of the most devastating fungal diseases and poses a serious threat to the worldwide cultivation of oilseed Brassica including India. S. sclerotiorum pathogen usually infects the stem but in severe cases leaves and pods also affected at different developmental stages that deteriorate not only the oil quality but also causing the seed and oil yield losses up to 90% depending on the severity of the disease infestation. This study investigated the morphological and molecular characterization of pathogenic S. sclerotiorum (Lib) de Bary geographical isolates from oilseed Brassica including Brassica juncea (Indian mustard). The aim of this study was to compare isolates of S. sclerotiorum originated from different agro-climatic conditions and to analyse similarity or differences between them as well as to examine the virulence of this pathogen specifically in Brassica for the first time. The collection of S. sclerotiorum isolates from symptomatic Brassica plants was done and analyzed for morphological features, and molecular characterization. The virulence evaluation test of 65 isolates on four Brassica cultivars has shown 5 of them were highly virulent, 46 were virulent and 14 were moderately virulent. Phylogenetic analysis encompassing all the morphological features, SSR polymorphism, and ITS sequencing has shown the existence of high genetic diversity among the isolates that categorized all the isolates in three evolutionary lineages in the derived dendrogram. Further, genetic variability analysis based on sequences variation in ITS region of all the isolates has shown the existence of either insertions or deletions of the nucleotides in the ITS region has led to the interspecies variability and observed the variation were in a clade-specific manner. Together this analysis observed the existence of higher heterogeneity and genetic variability in S. sclerotiorum isolates collection and indicates the presence of clonal and sexual progenies of the pathogen in the mustard growing regions of India surveyed in this study. With a higher level of genetic variability and diversity among the S. sclerotiorum population needs robust screening approaches to identify the donor parent and utilize them in resistance breeding program for effectively counter the menace of stem rot disease in Brassica.

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Extra-large G-proteins influence plant response to Sclerotinia sclerotiorum by regulating glucosinolate metabolism in Brassica juncea.

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