TISSUE-SPECIFIC CROSSTALK OF ABSCISIC ACID AND AUXIN IN THE ARABIDOPSIS ROOTS

Abstract

ABA and auxin are known to interact in order to regulate root growth and development. Under abiotic stresses, ABA level increases, leading to suppression of auxin signaling and auxin responses in Arabidopsis. A study of ABA-auxin crosstalk involving ABF3 and AXR3, was carried out. AXR3, a known negative regulator of auxin responses, is connected to auxin signaling. Auxin rapidly induces AXR3 expression, but its short-lived protein product is degraded under higher auxin concentrations. Noticeably, ABA significantly induces AXR3 expression via the transcription factor ABF3. Promoter of AXR3 consists of three ABREs, where ABF3 binds and upregulates AXR3 expression. Hence, by upregulating AXR3, ABA retards auxin signaling. Moreover, auxin also upregulates the expression of ABF3, which represents a novel mechanism of upregulating AXR3 expression and, regulating critical auxin responses in the roots. Our study established a novel molecular mechanism for the ABA-auxin crosstalk involved during stress conditions in Arabidopsis roots.