OsNF-YC2 and OsNF-YC4 proteins inhibit flowering under long-day conditions in rice

Abstract

Plant NUCLEAR FACTOR Y (NF-Y) transcription factors control numerous developmental processes by forming heterotrimeric complexes, but little is known about their roles in flowering in rice. In this study, it is shown that some subunits of OsNF-YB and OsNF-YC interact with each other, and among them, OsNF-YC2 and OsNF-YC4 proteins regulate the photoperiodic flowering response of rice. Protein interaction studies showed that the physical interactions occurred between the three OsNF-YC proteins (OsNF-YC2, OsNF-YC4 and OsNF-YC6) and three OsNF-YB proteins (OsNF-YB8, OsNF-YB10 and OsNF-YB11).Repression and overexpression of the OsNF-YC2 and OsNF-YC4 genes revealed that they act as inhibitors of flowering only under long-day (LD) conditions. Overexpression of OsNF-YC6, however, promoted flowering only under LD conditions, suggesting it could function as a flowering promoter. These phenotypes correlated with the changes in the expression of three rice flowering-time genes [Early heading date 1 (Ehd1), Heading date 3a (Hd3a) and RICE FLOWERING LOCUS T1 (RFT1)]. The diurnal and tissue-specific expression patterns of the subsets of OsNF-YB and OsNF-YC genes were similar to those of CCT domain encoding genes such as OsCO3, Heading date 1 (Hd1) and Ghd7. We propose that OsNF-YC2 and OsNF-YC4 proteins regulate the photoperiodic flowering response by interacting directly with OsNF-YB8, OsNF-YB10 or OsNF-YB11 proteins in rice.

Transcriptional and Post-transcriptional Mechanisms Limit Heading Date 1 (Hd1) Function to Adapt Rice to High Latitudes

“…Trimer formation with OsNF-YC2 and OsNF-YC4 could not be formally demonstrated because of auto-activation of yeast reporters. However, dimeric interactions between OsNF-YC2 and OsNF-YB8, OsNF-YB10 and OsNF-YB11 have been reported [65]. Most importantly, genetic evidences support a role for OsNF-YC2 in the control of flowering in rice [65].…”

“…However, dimeric interactions between OsNF-YC2 and OsNF-YB8, OsNF-YB10 and OsNF-YB11 have been reported [65]. Most importantly, genetic evidences support a role for OsNF-YC2 in the control of flowering in rice [65]. Transcriptional silencing of OsNF-YC2 by RNA-interference (RNAi) resulted in accelerated flowering under LD conditions, whereas its overexpression under the maize ubiquitin promoter strongly delayed flowering [65].…”

“…Most importantly, genetic evidences support a role for OsNF-YC2 in the control of flowering in rice [65]. Transcriptional silencing of OsNF-YC2 by RNA-interference (RNAi) resulted in accelerated flowering under LD conditions, whereas its overexpression under the maize ubiquitin promoter strongly delayed flowering [65]. A milder effect on LD repression of flowering has been reported for OsNF-YC4, whereas OsNF-YC6 seems to have no role in flowering time control [65].…”

“…Transcriptional silencing of OsNF-YC2 by RNA-interference (RNAi) resulted in accelerated flowering under LD conditions, whereas its overexpression under the maize ubiquitin promoter strongly delayed flowering [65]. A milder effect on LD repression of flowering has been reported for OsNF-YC4, whereas OsNF-YC6 seems to have no role in flowering time control [65]. Taken together, these data indicate that in rice cells multiple HFD scaffolds can form and possibly bind to NF-YA or CCT domain proteins to control heading.…”

CONSTANS Imparts DNA Sequence Specificity to the Histone Fold NF-YB/NF-YC Dimer

“…Specifically, there is well established evidence that different NF-Y HFD subunits are involved in the regulation of timing of flowering in Arabidopsis (Wenkel et al, 2006;Chen et al, 2007;Cai et al, 2007;Kumimoto et al, 2008Kumimoto et al, , 2010Hackenberg et al, 2012;Hou et al, 2014;Cao et al, 2014), rice (Oryza sativa; Dai et al, 2012;Wei et al, 2010;Yan et al, 2011;Feng et al, 2014;Chen et al, 2014;Kim et al, 2016;Hwang et al, 2016;Goretti et al, 2017), wheat (Triticum aestivum; , and tomato (Solanum lycopersicum; Ben-Naim et al, 2006). Wenkel et al originally observed homology between the CCT domain and the conserved domain of NF-YA, suggesting that CO and NF-YA might both bind DNA with NF-YB/NF-YC HFD dimers (Wenkel et al, 2006).…”