A new member of GHMP kinase family required for abscisic acid signaling in Arabidopsis
Hongping Chang^§, Congying Yuan^§, Dashi Yu, Yu Wang, Shuai Hu, Xuanming Liu, Xiushan Li, Xinhong Guo*^§

School of Biology, State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082 P.R.China
^§These authors contribute equally
*Corresponding author. gxh@hnu.edu.cn; xml05@126.com

Abstract
Numerous studies have indicated that phosphorylation is an important component of ABA signaling. The GHMP kinase family is a family of kinase enzymes. Members of this family include the galactokinase, homoserine kinase, mevalonate kinase, and phosphomevalonate kinase. Their main roles are to catalyze protein phosphorylation by transfering the phosphate of ATP to amino acid residues of the specific substrate, which were involved in a variety of signal transduction. Here, we showed that a new member of GHMP kinase family (GHMP1) controlled responses to ABA in seed germination, dormancy, and seedling growth in Arabidopsis thaliana. The results showed that two deletion mutants were less sensitive to exogenous ABA and NaCl in seed germination and root growth inhibition compared with wild-type. The real time PCR results showed that there were a high transcription level in roots and flowers, but low level in leaf, petiole, and stem. The expression of GHMP1 gene was induced by ABA and NaCl. The transcription levels of a series of stress response genes (abi1, abi2, KIN1/2, SOS2/3, OST1, RD29A/B, RAB18, RD22, DREB1/2A) related to ABA and salt responses were compared by real-time PCR between the two ghmp mutants and wild type. The distinct differences in transcription levels in these genes were displayed because of the deletion of GHMP1 gene. This work provided some invaluable references for the physiological functions of the other GHMP gene family members.

Key words: Arabidopsis; ABA; GHMP1; Physiological function