Analysis of the natural dehydration mechanism during middle and late stages of wheat seeds development by some physiological traits and iTRAQ-based proteomic

Jimai 22 wheat seeds collected at eight developmental stages [20-38 days after anthesis (daa)] were used to characterize the natural dehydration of wheat seeds. An iTRAQ-based quantitative proteomics technique was applied to identify differentially abundant proteins (DAPs) and evaluate several physiological traits at 20, 26, 32 and 38 daa. Superoxide dismutase and peroxidase activities as well as soluble sugar and soluble protein contents increased during dehydration, while the malondialdehyde content decreased. These results suggested that the antioxidant capacity of seeds increased during the dehydration process. A total of 128 proteins exhibited at least a 1.5-fold difference in abundance relative to the control levels in naturally dehydrating seeds. Forty of the DAPs were related to defense/stress responses. We observed an increase in the abundance of five late embryogenesis abundant proteins, five serpins, a heat shock cognate 70-kDa protein, and the 17.7-kDa Class I heat shock protein, with peak levels detected at 38 daa. Additionally, starch and sucrose metabolic activities were also associated with the natural dehydration of wheat seeds, with trehalose-6-phosphate synthase 7 increasing in abundance during the dehydration process.