RESUMO
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.
Assuntos
Proteínas de Arabidopsis/genética , Arabidopsis/genética , Regulação da Expressão Gênica de Plantas , Modelos Biológicos , Folhas de Planta/fisiologia , Fatores de Transcrição/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/metabolismo , Vetores Genéticos , Proteínas de Fluorescência Verde , Mutação/genética , Fotoperíodo , Folhas de Planta/citologia , Fatores de Transcrição/metabolismo , Transformação GenéticaRESUMO
The mechanism of guard cell development is currently attracting much interest. The recent use of Arabidopsis mutant plants has shed new light on the pathways that regulate the development and patterning of specialized cells such as guard cells, trichomes and roots hairs within the plant epidermis. Here, we review this literature focusing on the insights provided into guard cell development. We also discuss our current knowledge of how environmental variables may impact on guard cell development and, in particular, consider whether the composition of the epidermal waxes may be involved in this process.