Editors' ChoicePlant biology

Surviving the Drought

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Science's STKE  19 Jul 2005:
Vol. 2005, Issue 293, pp. tw265
DOI: 10.1126/stke.2932005tw265

Plants can tolerate dry conditions by closing pores, called stomata, between guard cells in leaves to reduce water loss. Cominelli et al. and Liang et al. report that transcription factors of the R2R3-MYB family in Arabidopsis thaliana are involved in control of guard-cell function and stomatal aperture. Cominelli et al. showed that the amount of transcript for AtMYB60 was rapidly decreased in guard cells in response to conditions that trigger stomatal closure--abscisic acid (ABA), dehydration, or darkness. Conditions (blue or white light) that promoted stomatal opening were associated with an increase in the abundance of the AtMYB60 transcript. Plants deficient for AtMYB60 showed decreased stomatal opening in response to light and were more resistant to drought conditions than were wild-type plants. Investigation of the genes regulated by AtMYB60 by microarray analysis suggested that AtMYB60 regulated the expression of a gene for an aquaporin and several genes implicated in other stress responses. The MYB transcript identified by Liang et al., AtMYB61, exhibited the opposite effects on stomatal aperture. Overexpression of AtMYB61 resulted in warmer plants with smaller stomatal apertures, and loss of AtMYB61 resulted in cooler plants with larger stomatal apertures. Loss of AtMYB61 did not impair stomatal closure in response to ABA; thus, this MYB transcription factor appears to function in a pathway independent from ABA. Plants deficient for AtMYB61 also did not close stomata as much as wild-type plants when placed in the dark. The abundance of the AtMYB61 transcript exhibited diurnal variation, with the greatest abundance occurring in the middle of the dark period. Thus, AtMYB61 appears to participate in an ABA-independent pathway that decreases stomatal aperture in response to darkness, whereas AtMYB60 appears to promote stomatal opening and is down-regulated by stimuli that activate ABA signaling.

E. Cominelli, M. Galbiati, A. Vavasseur, L. Conti, T. Sala, M. Vuylsteke, N. Leonhardt, S. L. Dellaporta, C. Tonelli, A guard-cell-specific MYB transcription factor regulates stomatal movements and plant drought tolerance. Current Biol. 15, 1196-1200 (2005). [PubMed]

Y.-K. Liang, C. Dubos, I. C. Dodd, G. H. Holroyd, A. M. Hetherington, M. M. Campbell, AtMYB61, an R2R3-MYB transcription factor controlling stomatal aperture in Arabidopsis thaliana. Current Biol. 15, 1201-1206 (2005). [PubMed]

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