title: Dynamic proteomic analysis reveals a switch between central carbon metabolism and alcoholic fermentation in rice filling grains.
abstract: Accumulation of reserve materials in filling grains involves the coordination of different metabolic and cellular processes, and understanding the molecular mechanisms underlying the interconnections remains a major challenge for proteomics. Rice (Oryza sativa) is an excellent model for studying grain filling because of its importance as a staple food and the available genome sequence database. Our observations showed that embryo differentiation and endosperm cellularization in developing rice seeds were completed approximately 6 d after flowering (DAF); thereafter, the immature seeds mainly underwent cell enlargement and reached the size of mature seeds at 12 DAF. Grain filling began at 6 DAF and lasted until 20 DAF. Dynamic proteomic analyses revealed 396 protein spots differentially expressed throughout eight sequential developmental stages from 6 to 20 DAF and determined 345 identities. These proteins were involved in different cellular and metabolic processes with a prominently functional skew toward metabolism (45%) and protein synthesis/destination (20%). Expression analyses of protein groups associated with different functional categories/subcategories showed that substantially up-regulated proteins were involved in starch synthesis and alcoholic fermentation, whereas the down-regulated proteins in the process were involved in central carbon metabolism and most of the other functional categories/subcategories such as cell growth/division, protein synthesis, proteolysis, and signal transduction. The coordinated changes were consistent with the transition from cell growth and differentiation to starch synthesis and clearly indicated that a switch from central carbon metabolism to alcoholic fermentation may be important for starch synthesis and accumulation in the developmental process.
authors.affiliation: Research Center of Molecular and Developmental Biology, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, China.
authors.forename: Sheng Bao
authors.initials: SB
authors.lastname: Xu
authors.forename: Tang
authors.initials: T
authors.lastname: Li
authors.forename: Zhu Yun
authors.initials: ZY
authors.lastname: Deng
authors.forename: Kang
authors.initials: K
authors.lastname: Chong
authors.forename: Yongbiao
authors.initials: Y
authors.lastname: Xue
authors.forename: Tai
authors.initials: T
authors.lastname: Wang