Regulation ofPYR/PYL/RCARABA receptors mRNA stability: involvement of miR5628 in decay ofPYL6mRNA

Abstract

ABSTRACTHormone signaling fine-tuning involves feedback regulatory loops. Abscisic acid (ABA) plays key functions in development and tolerance to abiotic stress. ABA is sensed by the PYR/PYL/RCAR receptors and it also represses their gene expression. Conversely, ABA inducesPP2Cphosphatases expression, which are negative regulators of the ABA signaling pathway. This feedback regulatory scheme is likely important for the modulation of ABA signal transduction. Here, we provide a new insight into the mechanisms underlying the ABA-induced negative control ofPYR/PYL/RCARexpression inArabidopsis thaliana. The strong and sustained repression ofPYR/PYL/RCARsrevealed by ABA time course treatment defines the regulation of receptors genes as an important step in resetting the ABA signaling pathway. Transcription inhibition by cordycepin showed that destabilization ofPYL1/4/5/6mRNA is involved in ABA-induced repression of these genes. Furthermore, genetic evidence indicated that decapping may play a role inPYL4/5/6mRNAs decay. In addition, we provide evidence that theArabidopsis-specificmicroRNA5628 (miR5628), which is transiently induced by the ABA core signaling pathway, guides the cleavage ofPYL6transcript in response to ABA. After cleavage, the resulting RISC 5’- and 3’-cleaved fragments ofPYL6mRNA may be degraded by exoribonuclease XRN4. MiR5628 is an evolutionary novelty that may contribute, with decapping and XRN4 activities, to enhancePYL6mRNA degradation. Thus, control of stability ofPYR/PYL/RCARtranscripts is an important step in maintaining homeostasis of ABA signaling.One Sentence SummaryAttenuation of ABA signaling involves destabilization ofPYL1/4/5/6transcripts. ABA core signaling induces miR5628 expression to enhancePYL6mRNA degradation in conjunction with decapping and XRN4 activities.