Effect of Drought Stress on Proteome of Maize Grain during Grain Filling

Based on isobaric tags for relative and absolute quantification (iTRAQ) technology, the proteome of grains of a maize cultivar Huangzao 4 under drought stress at grain filling stage was analyzed. The results show that under drought stress, 438 proteins were differentially expressed in the maize grains during grain filling. Among them, 200 were up-regulated and 238 were down-regulated. The gene ontology (GO) analysis shows that the biological processes in which differential proteins are more involved are cellular processes, metabolic processes and single biological processes; proteins in the cell component category are mainly distributed in cells, cell parts and organelles; and the proteins the molecular function category mainly possess catalytic activity and binding function. Differentially expressed proteins classified by COG are mainly involved in protein post-translational modification and transport, molecular chaperones, general functional genes, translation, ribosomal structure, biosynthesis, energy production and transformation, carbohydrate transport and metabolism, amino acid transport and metabolism, etc. The subcellular structure of the differentially expressed proteins is mainly located in the cell chloroplast and cytosol. The proportions are 35.01% and 30.21% respectively. KEGG metabolic pathway enrichment analysis shows that the differentially expressed proteins are mostly involved in antibiotic biosynthesis, microbial metabolism in different environments, and endoplasmic reticulum protein processing; the metabolic pathways with higher enrichment are the carbon fixation pathway and estrogen signaling pathway of prokaryotes; and the higher enrichment and greater significance are in the tricarboxylic acid cycle, carbon fixation of photosynthetic organisms and proteasome. The results of this study preliminarily reveal the adaptive mechanism of maize grains in response to drought stress during grain filling, providing a theoretical reference for maize drought-resistant molecular breeding.