Alanine aminotransferase 1 (OsAlaAT1) plays an essential role in the regulation of starch storage in rice endosperm. (November 2015)

• Record Type: Journal Article
• Authors: Yang, Jungil; Kim, Sung-Ryul; Lee, Sang-Kyu; Choi, Heebak; Jeon, Jong-Seong; An, Gynheung
• Is Part Of: Plant science. Volume 240(2015:Nov.)
• Page Start: 79
• Page End: 89
• Publication Date: 2015-11
• Subjects: Alanine aminotransferase -- Carbon metabolism -- Floury endosperm -- Rice -- Starch synthesis; Botany -- Periodicals; Botanique -- Périodiques; 580
• DOI: 10.1016/j.plantsci.2015.07.027
• Languages: English
• ISSNs: 0168-9452

Abstract

Highlights: OsAlaAT1 is predominantly expressed in developing seeds, which conferred white-core endosperm. The osalaat1 mutant has less amylose and its amylopectin is structurally altered. OsAlaAT1 has aminotransferase activity and glutamate levels were lower in the mutant seeds. OsPPDKB cause white-core endosperm and its transcripts were down-regulated in the osalaat1 . OsAlaAT1 and OsPPDKB function in the same pathway to modulate carbon metabolism during grain filling. Abstract: Alteration of storage substances, in particular the major storage form starch, leads to floury endosperm. Because floury mutants have physical attributes for milling processes, identification and characterization of those mutants are valuable. In this study we identified a floury endosperm mutant caused by a T-DNA insertion in O ryza s ativa ala nine-a minot ransferase1 ( OsAlaAT1 ). OsAlaAT1 is localized in the cytosol and has aminotransferase enzyme activity. The osalaat1 mutant has less amylose and its amylopectin is structurally altered. OsAlaAT1 is predominantly expressed in developing seeds during active starch synthesis. AlaAT catalyzes the interconversion of pyruvate to alanine, and this pathway is activated under low-oxygen conditions. Consistently, OsAlaAT1 is induced by such conditions. Expression of the starch synthesis genes AGPases, OsSSI, OsSSIIa, and OsPPDKB is decreased in the mutant. Thus, our observations suggest that OsAlaAT1 plays an essential role in starch synthesis in developing seeds that are exposed to low concentrations of oxygen.