Homodimerization of Ehd1 Is Required to Induce Flowering in Rice  

Abstract

In plants, flowering time is elaborately controlled by various environment factors. Ultimately, florigens such as FLOWERING LOCUS T (FT) or FT-like molecules induce flowering. In rice (Oryza sativa), Early heading date 1 (Ehd1) is a major inducer of florigen gene expression. Although Ehd1 is highly homologous to the type-B response regulator (RR) family in the cytokinin signaling pathway, its precise molecular mechanism is not well understood. In this study, we showed that the C-terminal portion of the protein containing the GARP DNA-binding (G) domain can promote flowering when overexpressed. We also observed that the N-terminal portion of Ehd1, carrying the receiver (R) domain, delays flowering by inhibiting endogenous Ehd1 activity. Ehd1 protein forms a homomer via a 16-amino acid region in the inter domain between R and G. From the site-directed mutagenesis analyses, we demonstrated that phosphorylation of the Asp-63 residue within the R domain induces the homomerization of Ehd1, which is crucial for Ehd1 activity. A type-A RR, OsRR1, physically interacts with Ehd1 to form a heterodimer. In addition, OsRR1-overexpressing plants show a late-flowering phenotype. Based on these observations, we conclude that OsRR1 inhibits Ehd1 activity by binding to form an inactive complex.

Antagonistic Transcription Factor Complexes Modulate the Floral Transition in Rice

“…Environmental signals ultimately converge on the transcriptional activation of Early heading date 1 (Ehd1), encoding a B-type response regulator unique to rice (Brambilla and Fornara, 2013;Doi et al, 2004;Cho et al, 2016). Transcription of Ehd1, Hd3a, and RFT1 thus correlates under SD in leaves, showing a transient induction that persists only for the time required to irreversibly commit flowering at the SAM (Galbiati et al, 2016;Doi et al, 2004;Cho et al, 2016;Komiya et al, 2008). Once a sufficient amount of Hd3a and/or RFT1 proteins reaches the SAM, expression of target genes that promote inflorescence formation is induced (Taoka et al, 2011;Tamaki et al, 2015).…”

RSL Class II Transcription Factors Guide the Nuclear Localization of RHL1 to Regulate Root Hair Development

“…Constructs harboring the fused Os07g39940-Myc and OsRHL1-HA were then cotransformed into those protoplasts. The positive control was OsEhd1, a homodimerforming protein (Cho et al, 2016). Here, the anti-Myc antibody not only immune-precipitated Os07g39940-Myc, but also coimmunoprecipitated OsRHL1-HA from the protein extracts ( Fig.…”

Chromatin interacting factor OsVIL2 increases biomass and rice grain yield

“…First‐strand cDNA was synthesized with 2 μg of total RNA and Moloney murine leukaemia virus reverse transcriptase (Promega, Madison, WI, USA; http://www.promega.com). Synthesized cDNA was prepared from leaf blades, and quantitative real‐time RT‐PCR was performed with a Rotor‐Gene 6000 (Corbett Research, Sydney, Australia; http://www.corbettlifescience.com), following protocols reported earlier (Cho et al ., ; Yang et al ., ). Rice OsUbi1 was used as an internal control.…”

“…The Co-IP assays were performed as reported earlier (Cho et al, 2016;Yoon et al, 2017). Briefly, fusion molecules were coexpressed in rice Oc cell protoplasts.…”