Combining extracellular matrix proteome and phosphoproteome of chickpea and meta-analysis reveal novel proteoforms and evolutionary significance of clade-specific wall-associated events in plant

Abstract

Extracellular matrix (ECM) plays central roles in cell architecture, innate defense andcell wall integrity (CWI) signaling. During transition to multicellularity, modulardomain structures of ECM proteins and proteoforms have evolved due to continuousadaptation across taxonomic clades under different ecological niche. Although thisincredible diversity has to some extent been investigated at protein level, extracellu-lar phosphorylation events and molecular evolution of ECM proteoform familiesremains unexplored. We developed matrisome proteoform atlas in a grain legume,chickpea and performed meta-analyses of 74 plant matrisomes. MS/MS analysisidentified 1,424 proteins and 315 phosphoproteins involved in diverse functions.Cross-species ECM protein network identified proteoforms associated with CWImaintenance system. Phylogenetic characterization of eighteen matrix protein fami-lies highlighted the role of taxon-specific paralogs and orthologs. Novel informationwas acquired on gene expansion and loss, co-divergence, sub functionalization andneofunctionalization during evolution. Modular networks of matrix protein familiesand hub proteins showed higher diversity across taxonomic clades than amongorgans. Furthermore, protein families differ in nonsynonymous to synonymous sub-stitution rates. Our study pointed towards the matrix proteoform functionality,sequence divergence variation, interactions between wall remodelers and molecularevolution using a phylogenetic framework. This is the first report on comprehensivematrisome proteoform network illustrating presence of CWI signaling proteins inland plants.