A dual role for MYB60 in stomatal regulation and root growth of Arabidopsis thaliana under drought stress.

In response to environmental challenges, plant cells activate several signaling pathways that trigger the expression of transcription factors. Arabidopsis MYB60 was reported to be involved in stomatal regulation under drought conditions. Here, two splice variants of the MYB60 gene are shown to play a crucial role in stomatal movement. This role was demonstrated by over-expressing each variant, resulting in enhanced sensitivity to water deficit stress. The MYB60 splice variants, despite the fact that one of which lacks the first two exons encoding the first MYB DNA binding domain, both localize to the nucleus and promote guard cell deflation in response to water deficit. Moreover, MYB60 expression is increased in response to a low level of ABA and decreased in response to high level of ABA. At initial stage of drought stress, the plant system may modulate the root growth behavior by regulating MYB60 expression, thus promotes root growth for increased water uptake. In contrast, severe drought stress inhibits the expression of the MYB60 gene, resulting in stomatal closure and root growth inhibition. Taken together, these data indicate that MYB60 plays a dual role in abiotic stress responses in Arabidopsis through its involvement in stomatal regulation and root growth.