The DELLA-CONSTANS Transcription Factor Cascade Integrates Gibberellic Acid and Photoperiod Signaling to Regulate Flowering

Abstract

Gibberellin (GA) and photoperiod pathways have recently been demonstrated to collaboratively modulate flowering under long days (LDs). However, the molecular mechanisms underlying this collaboration remain largely unclear. In this study, we found that GA-induced expression of FLOWERING LOCUS T (FT) under LDs was dependent on CONSTANS (CO), a critical transcription factor positively involved in photoperiod signaling. Mechanistic investigation revealed that DELLA proteins, a group of crucial repressors in GA signaling, physically interacted with CO. The DELLA-CO interactions repressed the transcriptional function of CO protein. Genetic analysis demonstrated that CO acts downstream of DELLA proteins to regulate flowering. Disruption of CO rescued the earlier flowering phenotype of the gai-t6 rga-t2 rgl1-1 rgl2-1 mutant (dellap), while a gain-of-function mutation in GA INSENSITIVE (GAI, a member of the DELLA gene) repressed the earlier flowering phenotype of CO-overexpressing plants. In addition, the accumulation of DELLA proteins and mRNAs was rhythmic, and REPRESSOR OF GA1-3 protein was noticeably decreased in the long-day afternoon, a time when CO protein is abundant. Collectively, these results demonstrate that the DELLA-CO cascade inhibits CO/FT-mediated flowering under LDs, which thus provide evidence to directly integrate GA and photoperiod signaling to synergistically modulate flowering under LDs.

DELAYED HEADING DATE1 interacts with OsHAP5C/D, delays flowering time and enhances yield in rice

“…DHD1 and DHD1L may be involved in other special rice flowering pathways. The homologous of DHD1, DELLA proteins, are involved in the GA flowering pathway in Arabidopsis thaliana (Wang et al ., ). DELLA protein REPRESSOR of ga1‐3 (RGA) can be degraded by GA (Willige et al ., ) while ABA promotes its accumulation (Guo et al ., ).…”

Arabidopsis VQ18 and VQ26 proteins interact with ABI5 transcription factor to negatively modulate ABA response during seed germination

“…The amiR‐VQ18 and amiR‐VQ26 sequences were designed by using WMD3 (http://wmd3.weigelworld.org), with the miR319a backbone to drive their expression (Liang et al ., , ), and the amiR‐VQ18 or amiR‐VQ26 precursors were cloned into the pOCA30 vector (Jiang et al ., ). To generate VQ18 or VQ26 overexpression transgenic plants, the full‐length cDNA of VQ18 or VQ26 was cloned into the binary vector pOCA30 in the sense orientation behind the CaMV 35S promoter (Wang et al ., ). Those constructs were transformed into Arabidopsis plants using the Agrobacterium tumefaciens ‐mediated flower dip method (Bechtold et al ., ; Wang et al ., ).…”

New insights into gibberellin signaling in regulating flowering in Arabidopsis

“…In the GA‐deficient mutant ga1‐3 or the plants with impaired GA signaling ( dellaΔ17 ), FT expression is largely suppressed, whereas FT expression is dramatically induced in plants under exogenous GA treatment or in mutants with constantly active GA (Galvão et al ; Porri et al ; Hou et al ). DELLAs are widely involved in GA‐mediated promotion of FT expression through negatively affecting several FT activators, such as CO. DELLAs directly bind to CO through its CCT (CONSTANS, CONSTANS‐LIKE, TOC1) domain and sequester CO from binding to the FT promoter, thus, downregulating FT mainly under LDs (Figure A) (Wang et al ; Xu et al ). Furthermore, by competitively binding to CO, DELLAs may inhibit the interaction between CO and Nuclear factor Y (NF‐Y) subunit B (NF‐YB), thus suppressing flowering (Xu et al ).…”