한빛사 논문
Zheng-Yi Xu,a Kwang Hee Lee,a Ting Dong,b Jae Cheol Jeong,c,1 Jing Bo Jin,d Yuri Kanno,e Dae Heon Kim,a Soo Youn Kim,b Mitsunori Seo,e Ray A. Bressan,f Dae-Jin Yun,c and Inhwan Hwanga,b,2
aDivision of Molecular and Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea
bDivision of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
cPlant Molecular Biology and Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea
dKey Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Science, Beijing 100093, China
eDormancy and Adaptation Research Unit, RIKEN Plant Science Center, Yokohama, Kanagawa 230-0045, Japan
fCenter for Plant Environmental Stress Physiology, Purdue University, West Lafayette, Indiana 4707-2010
1Current address: Environmental Biotechnology Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon 305-806, Korea.
2Corresponding author
Abstract
The phytohormone abscisic acid (ABA) plays a critical role in various physiological processes, including adaptation to abiotic stresses. In Arabidopsis thaliana, ABA levels are increased both through de novo biosynthesis and via b-glucosidase homolog1 (BG1)-mediated hydrolysis of Glc-conjugated ABA (ABA-GE). However, it is not known how many different b-glucosidase proteins produce ABA from ABA-GE and how the multiple ABA production pathways are coordinated to increase ABA levels. Here, we report that a previously undiscovered b-glucosidase homolog, BG2, produced ABA by hydrolyzing ABA-GE and plays a role in osmotic stress response. BG2 localized to the vacuole as a high molecular weight complex and accumulated to high levels under dehydration stress. BG2 hydrolyzed ABA-GE to ABA in vitro. In addition, BG2 increased ABA levels in protoplasts upon application of exogenous ABA-GE. Overexpression of BG2 rescued the bg1 mutant phenotype, as observed for the overexpression of NCED3 in bg1 mutants. Multiple Arabidopsis bg2 alleles with a T-DNA insertion in BG2 were more sensitive to dehydration and NaCl stress, whereas BG2 overexpression resulted in enhanced resistance to dehydration and NaCl stress. Based on these observations, we propose that, in addition to the de novo biosynthesis, ABA is produced in multiple organelles by organelle-specific b-glucosidases in response to abiotic stresses.
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