Role of rice cytosolic hexokinase OsHXK7 in sugar signaling and metabolism

作     者：Hyun-Bi Kim Jung-Il Cho Nayeon Ryoo Dong-Ho Shin Youn-Il Park Yong-Sic Hwang Sang-Kyu Lee Gynheung An Jong-Seong Jeon 

作者机构：Crop Biotech Institute & Graduate School of BiotechnologyKyung Hee University National Academy of Agricultural ScienceRural Development Administration Center for NeuroscienceKorea Institute of Science and Technology Department of BiologyChungnam National University Department of Bioscience and BiotechnologyKonkuk University 

出 版 物：《Journal of Integrative Plant Biology》 (植物学报（英文版）)

年 卷 期：2016年第58卷第2期

页      面：127-135页

核心收录：

学科分类：09[农学] 0901[农学-作物学] 

基　　金：supported by grants from the Next Generation Bio Green 21 program,Rural Development Administration(PJ0110182015) the Mid-Career Researcher Program of the National Research Foundation(NRF-2013R1A2A2A01068887) 

主　　题：Germination metabolism OsHXK7 O2 deficiency rice signaling sugar 

摘      要：We characterized the function of the rice cytosolic hexokinase OsHXK7 （Qryza sativa HexokindseZ）, which is highly upregulated when seeds germinate under O2- deficient conditions. According to transient expression assays that used the promoter：luciferase fusion construct, OsHXK7 enhanced the glucose （Glc）-dependent repression of a rice n-amylase gene （RAmy3D） in the mesophyll protoplasts of maize, but its catalytically inactive mutant alleles did not. Consistently, the expression of OsHXK7, but not its catalytically inactive alleles, complemented the Arabidopsis glucose insensitive2-1 （gin2-1） mutant, thereby resulting in the wild type characteristics of Glc-dependent repression, seedling development, and plant growth. Interestingly, OsHXK7-mediated Glc-dependent repression was abolished in the O2-deficient mesophyll protoplasts of maize. This result provides compelling evidence that OsHXK7 functions in sugar signaling via a glycolysis-dependent manner under normal conditions, but its signaling role is suppressed when O2 is deficient. The germination of two null OsHXK7 mutants, oshxk7-1 and oshxk7-2, was affected by O2 deficiency, but overexpression enhanced germination in rice. This result suggests the distinct role that OsHXK7 plays in sugar metabolism and efficient germination by enforcing glycolysis-mediated fermentation in O2-deficient rice.