Integrated seed proteome and phosphoproteome analyses reveal interplay of nutrient dynamics, carbon-nitrogen partitioning and oxidative signaling in chickpea

Abstract

Nutrient dynamics in storage organs is a complex developmental process that requires coordinated interactions of environmental, biochemical, and genetic factors. Although sink organ developmental events have been identified, our understanding of translational and post‐translational regulation of reserve synthesis, accumulation and utilization in legume crops is limited. To understand nutrient dynamics during embryonic and cotyledonary photoheterotrophic transition to mature and germinating autotrophic seeds, an integrated proteomics and phosphoproteomics study in six sequential seed developmental stages in chickpea was performed. MS/MS analyses identified 109 unique nutrient‐associated proteins (NAPs) involved in metabolism, storage and biogenesis, and protein turnover. Differences and similarities in 60 nutrient‐associated phosphoproteins (NAPPs) containing 93 phosphosites were compared with NAPs. Data revealed accumulation of carbon‐nitrogen metabolic and photosynthetic proteoforms during seed filling. Furthermore, enrichment of storage proteoforms and protease inhibitors was associated with cell expansion and seed maturation. Finally, combined proteoforms network analysis identified three significant modules, centered around malate dehydrogenase, HSP70, triose phosphate isomerase and vicilin. Novel clues suggest that ubiquitin‐proteasome pathway regulates nutrient reallocation. Second, increased abundance of NAPs/NAPPs related to oxidative and serine/threonine signalling indicate direct interface between redox sensing and signaling during seed development. Taken together, nutrient signals act as metabolic and differentiation determinant governing storage organ reprogramming.