Mechanistic Insights into Soybean-Macrophomina Interactions in the Cell Wall Interface: Glycomics and Proteomics Approach

Abstract

Macrophomina phaseolina is a climate change-relevant necrotrophic plant fungal pathogen whose virulence increases with high temperature and drought conditions. M. phaseolina causes charcoal rot (CR) disease in several crops, including soybean, and has become a serious threat under changing climatic conditions. So far, no reliable source of resistance has been identified in soybean or other crops to tackle the pathogen. Hence, the mechanistic details of M. phaseolina-soybean interaction are needed to formulate strategies for improving disease resistance.

My research group employs Glycomics and proteomic approaches to identify novel candidates in soybean for improving resistance against charcoal rot disease. During fungal colonization, the initial contact with a root cell is initiated in the apoplast (intercellular spaces) and extracellular polysaccharides surrounding the fungal hyphae are the first components that physically interact with root cells. In the aspect of Carbohydrate Metabolic Processes (CMP), many studies have been focused on chitin, a structural polysaccharide that is derived from the inner insoluble cell wall layer of fungus. However, our recent structural studies have indicated that β-glucans are the abundant polysaccharide in the fungal cell walls (approx. 70-80%) and chitin contributes only a minor proportion. Furthermore, we have unraveled that the structural features of the cell wall layer of plant-associated fungal hyphae are encased by an additional gel-like soluble extracellular polysaccharide (EPS) matrix that is rich in polymorphic β-glucans with varying glycosidic linkages. Profiling the glycan repertoire in the EPS matrix of M. phaseolina has revealed several important polysaccharides that might play a significant role during colonization and are remodelled under high temperature conditions. We also performed apoplastic proteome analysis and we identified the CAZymes that are involved in the processing of these glycan components. Furthermore, our AlphaFold analysis of the soybean apoplastic root proteome has revealed several interesting SUSS effectors, protease-inhibitor interactions, and protein-protein interactions that occur in the cell wall interface. Currently, we are taking these leads into in-depth mechanistic studies for tackling M. phaseolina.