Structural, functional and proteomic changes of proteins during rice yellowing

High temperature storage (40 °C, 60 % relative humidity, 6 months) induces rice yellowing and affects protein properties. Physiochemical analysis revealed increased disulfide bonds, particle size, and surface hydrophobicity in yellowed rice protein, alongside reduced water-holding capacity and emulsifiability. TMT-based LC-MS/MS proteomics analysis found most differentially expressed proteins (DEPs) in yellowed rice were upregulated (>1.3-fold, P < 0.05), peaking in the middle stage of yellowing. Stress-responsive DEPs were the most abundant, among which heat shock proteins and late embryogenesis abundant proteins could resist heat stress during yellowing. The up-regulation of protein disulfide isomerases (PDI, e.g., ∼1.5-fold) aligned with enhanced protein aggregation, consistent with their role in misfolded protein response. Metabolic association among DEPs suggested greater energetic demand of yellowed rice. Downstream metabolism of glycolysis was more active in the middle and late stages of yellowing. Proteasome-mediated protein degradation appeared critical for yellowing, while elevated secondary metabolism contributed to yellow pigment formation.