AtMYB61, an R2R3-MYB Transcription Factor Controlling Stomatal Aperture in Arabidopsis thaliana

Abstract

Stomata, dynamic pores found on the surfaces of plant leaves, control water loss from the plant and regulate the uptake of CO(2) for photosynthesis. Stomatal aperture is controlled by the two guard cells that surround the stomatal pore. When the two guard cells are fully turgid, the pore gapes open, whereas turgor loss results in stomatal closure. In order to set the most appropriate stomatal aperture for the prevailing environmental conditions, guard cells respond to multiple internal and external signals. Although much is known about guard-cell signaling pathways, rather little is known about how changes in gene expression are involved in the control of stomatal aperture. We show here that AtMYB61 (At1g09540), a gene encoding a member of the Arabidopsis thaliana R2R3-MYB family of transcription factors, is specifically expressed in guard cells in a manner consistent with involvement in the control of stomatal aperture. Gain-of-function and loss-of-function mutant analyses reveal that AtMYB61 expression is both sufficient and necessary to bring about reductions in stomatal aperture with consequent effects on gas exchange. Taken together, our data provide evidence that AtMYB61 encodes the first transcription factor implicated in the closure of stomata.

Overexpression of AtMYB44 Enhances Stomatal Closure to Confer Abiotic Stress Tolerance in Transgenic Arabidopsis

“…In addition, the Arabidopsis mutant hos10-1 (conferring high expression of osmotically responsive genes) exhibits altered expression of ABA-responsive genes, showing dramatically reduced capacity for cold acclimation and hypersensitivity to dehydration and salinity . As reported recently, AtMYB60 is specifically expressed in guard cells and involved in light-induced opening of stomata (Cominelli et al, 2005), whereas AtMYB61 is expressed under conditions necessary for dark-induced stomatal closure (Liang et al, 2005).…”

“…For instance, overexpression of AtMYB61 (Liang et al, 2005), which controls dark-induced stomatal closure, resulted in smaller stomatal apertures in transgenic Arabidopsis. Mutations on AtMYB60, which controls stomatal opening (Cominelli et al, 2005), OST1, which encodes a protein kinase involved in ABAmediated stomatal closure (Xie et al, 2006), and HT1, which encodes a kinase involved in stomatal movements in response to CO 2 (Hashimoto et al, 2006), also resulted in smaller stomatal apertures, respectively.…”

MYB transcription factor genes as regulators for plant responses: an overview

“…Zhong et al (2008) proposed that AtMYB52, AtMYB54 and AtMYB69 regulated lignin, xylan and cellulose biosynthesis, and cellulose biosynthesis. AtMYB61 plays a pleiotropic role, influencing lignin deposition (Newman et al 2004), mucilage production (Penfield et al 2001) and stomatal aperture (Liang et al 2005), suggesting that it might act upstream of the different pathways by regulating carbon allocation. The R2R3-MYB proteins of subgroup 12 i.e.…”

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

“…Hydrogen peroxide (H 2 O 2 ) inhibits blue light-induced phosphorylation of H + -ATPase (activation), and consequently attenuates blue light-dependent H + pumping (Zhang et al, 2004). MYB60 and MYB61, two members of the R2R3-MYB family of transcription factors, are specifically expressed in guard cells and regulate the stomatal aperture (Cominelli et al, 2005;Liang et al, 2005). MYB60 is a positive regulator of stomatal opening, and its expression is induced by blue light and rapidly down-regulated by dehydration (Cominelli et al, 2005).…”