Antagonistic Transcription Factor Complexes Modulate the Floral Transition in Rice

Abstract

Plants measure day or night lengths to coordinate specific developmental changes with a favorable season. In rice (Oryza sativa), the reproductive phase is initiated by exposure to short days when expression of HEADING DATE 3a (Hd3a) and RICE FLOWERING LOCUS T 1 (RFT1) is induced in leaves. The cognate proteins are components of the florigenic signal and move systemically through the phloem to reach the shoot apical meristem (SAM). In the SAM, they form a transcriptional activation complex with the bZIP transcription factor OsFD1 to start panicle development. Here, we show that Hd3a and RFT1 can form transcriptional activation or repression complexes also in leaves and feed back to regulate their own transcription. Activation complexes depend on OsFD1 to promote flowering. However, additional bZIPs, including Hd3a BINDING REPRESSOR FACTOR1 (HBF1) and HBF2, form repressor complexes that reduce Hd3a and RFT1 expression to delay flowering. We propose that Hd3a and RFT1 are also active locally in leaves to fine-tune photoperiodic flowering responses.

Contributions of Adaptive Plant Architecture to Transgressive Salinity Tolerance in Recombinant Inbred Lines of Rice: Molecular Mechanisms Based on Transcriptional Networks

“…This network of 118 constitutively expressed genes is enriched with molecular functions such as response to photo-oxidative stress, proteasome assembly, spindle assembly, photosystem I assembly, and stomatal complex development ( Figure 7B). Genes involved in floral organ development such as FRIGIDA-like protein (Os03t0794900-03), HD3A (Os06t0157700-01; heading date), and OsFD5 (Os06t0724000-01; homolog of OsFD1) were also quite prominent in this network ( Supplementary Table 3; Tamaki et al, 2007;Choi et al, 2011;Brambilla et al, 2017). These flowering regulator genes had stable expression in the transgressive super-tolerant FL510, but various patterns of upregulation were evident in the other genotypes, suggestive of perturbed developmental programming due to salt stress.…”

Genes of the RAV Family Control Heading Date and Carpel Development in Rice

“…Intriguingly, FT-like proteins do not have DNA binding activity per se and must interact with bZIP transcription factors (TFs), i.e. FLOWERING LOCUS D (FD) in Arabidopsis and OsFD1 in rice (Abe et al, 2005;Wigge et al, 2005;Taoka et al, 2011;Brambilla et al, 2017;Collani et al, 2019), to activate the expression of downstream genes. The interaction of FT and FD proteins require the 14-3-3 adaptor proteins for the formation of an active Floral Activation Complex (FAC; Taoka et al, 2011;Collani et al, 2019), which in Arabidopsis directly activates the FM identity gene AP1 (Wigge et al, 2005), whereas the rice FAC complex induces the expression of the AP1-like genes OsMADS14/15/18 and the SEPALLATA-like gene OsMADS34 that are required for the specification of IM identity (Kobayashi et al, 2012;Gómez-Ariza et al, 2019) The florigens also mediate the transcriptional repression of PINE, a gene encoding a Zinc Finger type TF involved in the negative regulation of stem elongation.…”

ClCRY2 facilitates floral transition in Chrysanthemum lavandulifolium by affecting the transcription of circadian clock-related genes under short-day photoperiods

“…The results inferred that ClCRY2 acts as a floral inducer by activating ClFT1 transcription. A previous study showed that the induction of homologous FT genes results from the integration of photoperiodic information with diurnal timing set by the plant’s circadian clock 61 . Therefore, we tested the changes in the expression patterns of circadian clock-related genes and ClCOL s. The results revealed that the expression levels of ClPRR5 , ClZTL , ClFKF1 , ClGI-1 , ClGI-2 , ClCOL1 , ClCOL4 , and ClCOL5 were also upregulated in ClCRY2 -OE C. lavandulifolium compared with the WT plants (Fig.…”