Matiolli, C. C. | Search bioRxiv

bioRxiv2023

Regulation of PYR/PYL/RCAR ABA receptors mRNA stability: involvement of miR5628 in decay of PYL6 mRNA

Hormone 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 induces PP2C phosphatases 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 of PYR/PYL/RCAR expression in Arabidopsis thaliana. The strong and sustained repression of PYR/PYL/RCARs revealed 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 of PYL1/4/5/6 mRNA is involved in ABA-induced repression of these genes. Furthermore, genetic evidence indicated that decapping may play a role in PYL4/5/6 mRNAs decay. In addition, we provide evidence that the Arabidopsis-specific microRNA5628 (miR5628), which is transiently induced by the ABA core signaling pathway, guides the cleavage of PYL6 transcript in response to ABA. After cleavage, the resulting RISC 5- and 3-cleaved fragments of PYL6 mRNA may be degraded by exoribonuclease XRN4. MiR5628 is an evolutionary novelty that may contribute, with decapping and XRN4 activities, to enhance PYL6 mRNA degradation. Thus, control of stability of PYR/PYL/RCAR transcripts is an important step in maintaining homeostasis of ABA signaling. One Sentence SummaryAttenuation of ABA signaling involves destabilization of PYL1/4/5/6 transcripts. ABA core signaling induces miR5628 expression to enhance PYL6 mRNA degradation in conjunction with decapping and XRN4 activities.

plant biology↗

bioRxiv2020

SUMOylation of rice DELLA SLR1 modulates transcriptional responses and improves yield under salt stress

DELLA proteins modulate GA signalling and are major regulators of plant plasticity to endure stress. DELLAs are mostly regulated at the post-translational level, and their activity relies on the interaction with upstream regulators and transcription factors (TFs). SUMOylation is a post-translational modification (PTM) capable of changing protein interaction and found to influence DELLA activity in Arabidopsis. We determined that SUMOylation of the single rice DELLA SLENDER RICE1 (SLR1) occurs in a lysine residue different from the one previously identified in Arabidopsis REPRESSOR OF GA (RGA). Remarkably, artificially increasing SUMOylated SLR1 (SUMO1SLR1) levels attenuated the penalty of salt stress on plant yield. Gene expression analysis revealed that the overexpression of SUMOylated SLR1 regulates key dioxygenases that modulate active GA levels, namely GA20ox2 and GA2ox3, which could partially explain the sustained productivity upon salt stress imposition. Besides, SLR1 SUMOylation blocked the interaction with the growth regulator YAB4, which may fine-tune GA20ox2 expression. Mechanistically, we propose that SLR1 SUMOylation disrupts the interaction with members of several transcription factor families to modulate gene expression. We found that SLR1 SUMOylation represents a novel mechanism modulating DELLA activity, which attenuates the impact of stress on plant performance. One sentence summaryRice plants show increased yield under salt stress when its gibberellin transcriptional regulator DELLA protein is artificially SUMOylated.

plant biology↗