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Role of cytokinin responsive two-component system in ABA and osmotic stress signalings

Lam-Son Phan Tran, Kazuo Shinozaki and Kazuko Yamaguchi-Shinozaki

The two-component signaling systems (TCSs), which mediate the histidine-aspartate signaling, control diverse biological processes of many organisms, including cell division, cell growth and proliferation, and responses to environmental stimuli and growth regulators. We have provided in planta evidence that the cytokinin (CK) responsive TCS mediates abscisic acid (ABA) and osmotic stress responses. By using loss-of-function approach we have demonstrated that the three cytokinin (CK) receptor histidine kinases AHK2, AHK3 and AHK4/CRE1 act as negative regulators in ABA, drought and high salinity stress signalings. Genome-wide expression profiling of the stress-tolerant double mutant suggested that CK receptor kinases mediate osmotic stress response in both an ABA-dependent and ABA-independent manner. Additionally, we showed evidence as for the role of CK in mediating stress responses, judging from the fact that AHK4 requires the CK to function as a negative regulator in osmotic stress response. Our results suggested that cross-talks exist among CK, ABA and osmotic stress signaling pathways, and that CK signaling and CK metabolism may play crucial roles not only in plant growth and development but also in osmotic stress signaling.

Tran LS, Urao T, Qin F, Maruyama K, Kakimoto T, Shinozaki K, Yamaguchi-Shinozaki K. Functional analysis of AHK1/ATHK1 and cytokinin receptor histidine kinases in response to abscisic acid, drought, and salt stress in Arabidopsis. Proc Natl Acad Sci USA 2007; 104:20623-8.

Authors

Lam-Son Phan Tran Corresponding author: tran@psc.riken.jp

RIKEN Plant Science Center, Signaling Pathway Research Unit, 1-7-22, Suehiro-cho, Tsurumi, Yokohama Japan

Kazuo Shinozaki

RIKEN Plant Science Center, Gene Discovery Research Group, 1-7-22, Suehiro-cho, Tsurumi, Yokohama Japan

Kazuko Yamaguchi-Shinozaki

Graduate School of Agricultural and Life Science University of Tokyo, Tokyo 113-8657, Japan; Japan International Center of Agricultural Sciences, Tsukuba, Ibaraki, Japan