CYCLIN H;1 Regulates Drought Stress Responses and Blue Light-Induced Stomatal Opening by Inhibiting Reactive Oxygen Species Accumulation in Arabidopsis

Xiao Feng Zhou,Jing Bo Jin,Ray A Bressan,Yin Hua Jin,Paul M Hasegawa,Chan Yul Yoo,Woe-Yeon Kim,Xiao-Li Lin,Dae-Jin Yun

doi:10.1104/pp.113.215798

Abstract

Arabidopsis (Arabidopsis thaliana) CYCLIN-DEPENDENT KINASE Ds (CDKDs) phosphorylate the C-terminal domain of the largest subunit of RNA polymerase II. Arabidopsis CYCLIN H;1 (CYCH;1) interacts with and activates CDKDs; however, the physiological function of CYCH;1 has not been determined. Here, we report that CYCH;1, which is localized to the nucleus, positively regulates blue light-induced stomatal opening. Reduced-function cych;1 RNA interference (cych;1 RNAi) plants exhibited a drought tolerance phenotype. CYCH;1 is predominantly expressed in guard cells, and its expression was substantially down-regulated by dehydration. Transpiration of intact leaves was reduced in cych;1 RNAi plants compared with the wild-type control in light but not in darkness. CYCH;1 down-regulation impaired blue light-induced stomatal opening but did not affect guard cell development or abscisic acid-mediated stomatal closure. Microarray and real-time polymerase chain reaction analyses indicated that CYCH;1 did not regulate the expression of abscisic acid-responsive genes or light-induced stomatal opening signaling determinants, such as MYB60, MYB61, Hypersensitive to red and blue1, and Protein phosphatase7. CYCH;1 down-regulation induced the expression of redox homeostasis genes, such as LIPOXYGENASE3 (LOX3), LOX4, ARABIDOPSIS GLUTATHIONE PEROXIDASE 7 (ATGPX7), EARLY LIGHT-INDUCIBLE PROTEIN1 (ELIP1), and ELIP2, and increased hydrogen peroxide production in guard cells. Furthermore, loss-of-function mutations in CDKD;2 or CDKD;3 did not affect responsiveness to drought stress, suggesting that CYCH;1 regulates the drought stress response in a CDKD-independent manner. We propose that CYCH;1 regulates blue light-mediated stomatal opening by controlling reactive oxygen species homeostasis.

Highlights

Arabidopsis (Arabidopsis thaliana) CYCLIN-DEPENDENT KINASE Ds (CDKDs) phosphorylate the C-terminal domain of the largest subunit of RNA polymerase II
These results reveal that water deficit represses CYCLIN H;1 (CYCH);1 expression, which leads to elevated levels of reactive oxygen species (ROS) in guard cells
To investigate the role of CYCH;1 in abiotic stress responses, we evaluated the expression of CYCH;1 in response to dehydration, abscisic acid (ABA), mannitol, and NaCl

Summary

Introduction

Arabidopsis (Arabidopsis thaliana) CYCLIN-DEPENDENT KINASE Ds (CDKDs) phosphorylate the C-terminal domain of the largest subunit of RNA polymerase II. To determine whether CYCH;1 is involved in light-induced stomatal opening, we measured the stomatal aperture widths of the cych;1 RNAi and wild-type plants in the dark and under both red and blue light (Mao et al, 2005). There were no significant differences in stomatal width between the mutants and the wild type in the dark and under red light (Fig. 3D), indicating that CYCH;1 mediates blue light-induced stomatal opening, consistent with the predominant expression of CYCH;1 in guard cells (Fig. 1B).

Results

Conclusion