SRK2C, a SNF1-related protein kinase 2, improves drought tolerance by controlling stress-responsive gene expression in Arabidopsis thaliana

^*Laboratory of Plant Molecular Biology, RIKEN Tsukuba Institute, 3-1-1 Kouyadai, Tsukuba 305-0074, Japan; ^†Plant Functional Genomics Group, RIKEN Genomics Sciences Center, 1-7-22 Suehiro-Cho, Tsurumi-ku, Yokohuma 203-0045, Japan; and ^‡Biological Resources Division, Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan

Communicated by Michael F. Thomashow, Michigan State University, East Lansing, MI, October 20, 2004 (received for review July 5, 2004)

Abstract

Protein phosphorylation/dephosphorylation are major signaling events induced by osmotic stress in higher plants. Here, we showed that a SNF1-related protein kinase 2 (SnRK2), SRK2C, is an osmotic-stress-activated protein kinase in Arabidopsis thaliana that can significantly impact drought tolerance of Arabidopsis plants. Knockout mutants of SRK2C exhibited drought hypersensitivity in their roots, suggesting that SRK2C is a positive regulator of drought tolerance in Arabidopsis roots. Additionally, transgenic plants with CaMV35S promoter::SRK2C-GFP displayed higher overall drought tolerance than control plants. Whereas stomatal regulation in 35S::SRK2C-GFP plants was not altered, microarray analysis revealed that their drought tolerance coincided with up-regulation of many stress-responsive genes, for example, RD29A, COR15A, and DREB1A/CBF3. From these results, we concluded that SRK2C is capable of mediating signals initiated during drought stress, resulting in appropriate gene expression. Our present study reveals new insights around signal output from osmotic-stress-activated SnRK2 protein kinase as well as supporting feasibility of manipulating SnRK2 toward improving plant osmotic-stress tolerance.

Footnotes

↵ § To whom correspondence should be addressed. E-mail: sinozaki{at}rtc.riken.jp.
Author contributions: T.U., R.Y., and K.S. designed research; T.U. performed research; T.U., R.Y., K.M., and K.Y.-S. contributed new reagents/analytic tools; T.U. and K.M. analyzed data; and T.U. wrote the paper.
Abbreviations: ABA, abscisic acid; CBF, C-repeat binding factor; DREB, dehydration-responsive element binding factor; MAPK, mitogen-activated protein kinase; SnRK2, Snf1-related protein kinase 2.