Background
Extracellular matrix (ECM) acts as a physical scaffold preventing recognition and entry of phyto-pathogens, while guard cell perceives and integrates signals metabolically. Wilt disease caused by Fusarium oxysporum is a major impediment for crop productivity. Although, chitosan and its acetylated form chitin are known MAMPs implicated in plant defense, the precise mechanism of chitosan triggered immunity (CTI) that leads to resistance against pathogens remains unknown. To understand the role of ECM and CTI against wilt disease, quantitative ECM proteome, metabolome along-with histological and biochemical analyses were performed in wilt resistant and susceptible chickpea (Cicer arietinum L.) cultivars.
Methods
Patho-stress was imposed on untreated and chitosan treated three-week-old chickpea seedlings and tissues were harvested at different post-infection time points. Stomatal mechanics were measured using GFS3000. ECM components were analysed in scanning electron microscopy and raman spectroscopy. Temporal ECM proteome and metabolome was developed using iTRAQ coupled Triple-TOF/MS and GC-MS analyses, respectively. Integrated global network was built and qRT-PCR analysis was performed to validate datasets.
Results
Morpho-histological examination revealed stomatal closure, reduced stomatal conductance and transpiration rate in chitosan-treated compared to untreated seedlings upon vascular fusariosis. ECM showed fortification leading to oligosaccharide signalling as documented by increased galactose, pectin and secondary carbohydrates. Multiomics using ECM proteomics and metabolomics identified 325 chitosan-triggered IRPs (CTIRPs), 65 CTIRMs that includes LysM domain protein, RLKs, sugars, organic acids and amino-acids linking ROS production, stomatal movements, root architecture. Immune-related correlation network identified functional hubs in CTI pathway. Data provide evidence that ROS, NO and eATP governs CTI. Induction of PR proteins, CAZymes and PAL were observed during CTI.
Conclusions
The study led us to discover the chitosan regulatory networks causing significant ECM and guard cell remodelling that translate ECM cues into cell fate decisions during fusariosis. ECM signaling and stomatal immunity plays pivotal role in CTI.