Research ArticlesBotany

bHLH Transcription Factors That Facilitate K+ Uptake During Stomatal Opening Are Repressed by Abscisic Acid Through Phosphorylation

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Science Signaling  18 Jun 2013:
Vol. 6, Issue 280, pp. ra48
DOI: 10.1126/scisignal.2003760

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Light induces the opening of stomata, pores in leaf epidermis that enable gas and water vapor exchange, whereas the hormone abscisic acid (ABA) causes stimulation of stomatal closure and inhibition of stomatal opening. Takahashi et al. identified a family of transcription factors called ABA-responsive kinase substrates (AKSs) that transcribed genes encoding potassium channels that promoted stomatal opening. ABA induced the phosphorylation of AKS transcription factors, preventing them from binding to the promoters of K+ channel–encoding genes and inducing a decrease in stomatal opening. Thus, AKS-mediated transcription stimulates stomatal opening, a process that is antagonized by ABA-induced phosphorylation of AKS transcription factors.

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