The DELLA family of transcription regulators functions as master growth repressors in plants by inhibiting phytohormone gibberellin (GA) signaling in response to developmental and environmental cues. DELLAs also play a central role in mediating cross-talk between GA and other signaling pathways via antagonistic direct interactions with key transcription factors. However, how these crucial protein-protein interactions can be dynamically regulated during plant development remains unclear. Here, we show that DELLAs are modified by the O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) SECRET AGENT (SEC) in Arabidopsis. O-GlcNAcylation of the DELLA protein REPRESSOR OF ga1-3 (RGA) inhibits RGA binding to four of its interactors-PHYTOCHROME-INTERACTING FACTOR3 (PIF3), PIF4, JASMONATE-ZIM DOMAIN1, and BRASSINAZOLERESISTANT1 (BZR1)—that are key regulators in light, jasmonate, and brassinosteroid signaling pathways, respectively. Consistent with this, the sec-null mutant displayed reduced responses to GA and brassinosteroid and showed decreased expression of several common target genes of DELLAs, BZR1, and PIFs. Our results reveal a direct role of OGT in repressing DELLA activity and indicate that O-GlcNAcylation of DELLAs provides a fine-tuning mechanism in coordinating multiple signaling activities during plant development.
Bibliographical noteFunding Information:
We thank Philip Benfey, Zhen-Ming Pei, and Jim Siedow for helpful comments on the manuscript. We also thank Jeongmoo Park for providing pGST-PIF3, Emily Jie-Ning Yang for her assistance in Y2H assays, and Jonathan Dayan and the Duke University Light Microscopy Core Facility for their help with confocal microscopy. This work was supported by the National Science Foundation (IOS-0641548 and MCB-0923723 to T.-P.S., and MCB-0516690, MCB-0820666, and MCB-1158089 to N.E.O.), U.S. Department of Agriculture (2014-67013-21548 to T.-P.S.), and National Institutes of Health (R01 GM100051 to T.-P.S.,and R01 GM037537 to D.F.H.).
- DELLA-interacting proteins
- Gibberellin signaling
- Hormone signaling
- O-GlcNAc transferase
- O-GlcNAcylation of DELLA
- SECRET AGENTs