Transcription factor ABI3 auto-activates its own expression during dehydration stress response

The transcription factor abscisic acid insensitive 3 (ABI3) has recently been shown to mediate the dehydration stress response in nonseed and seed plants by regulation of several downstream genes. Here, we show how ABI3 autoregulates its transcription in response to dehydration stress signalling. Autoactivation is primarily through the Sph/RY element CATGCA present at the promoter region of ABI3. Along with other known cis-elements found at the ABI3 promoter, CATGCA remains occluded by nucleosomes during transcription repression. The nucleosomes tend to reposit during active transcription and are associated with several histone modifications, such as H3K9 and K27 acetylations and H3K4 trimethylation. This work thus, reveals the genetic and epigenetic essentials required for expression of the ABI3 gene, a crucial factor regulating dehydration stress signalling in Arabidopsis thaliana.