OsCOL10, aCONSTANS-LikeGene, Functions as a Flowering Time Repressor Downstream ofGhd7in Rice

Abstract

Flowering time, or heading date, is a critical agronomic trait that determines the cropping season and regional adaptability, and ultimately grain yield in rice. A number of genes involved in photoperiodic flowering have been cloned and their roles in modulating expression of the flowering genes have been characterized to a certain extent. However, much less is known about the pathway in transmitting the day length response signal(s) to induce transition to reproductive growth. Here, we report a constitutive flowering repressor OsCOL10, which encodes a member of the CONSTANS-like (COL) family. Transgenic rice plants overexpressing OsCOL10 (driven by a strong promoter or by fusing it to the activation domain of VP64) showed delayed flowering time under both short and long days.OsCOL10 is affected by the circadian clock and is preferentially expressed in leaf mesophyll cells; it is localized to the nucleus and has transcriptional activation activity. Further studies show that OsCOL10 represses the expression of theFT-like genes RFT1 and Hd3a through Ehd1. Transcripts of OsCOL10 are more abundant in plants carrying a functional Ghd7 allele or overexpressing Ghd7 than in Ghd7-deficient plants, thus placing OsCOL10 downstream of Ghd7.Taking these findings together, we conclude that OsCOL10 functions as a flowering time repressor that links Ghd7 and Ehd1 in rice.

Complex interactions between day length and diurnal patterns of gene expression drive photoperiodic responses in a perennial C4 grass

“…Hd1 has dual functions on the flowering of rice that promotes heading under SD conditions but represses heading under LD conditions (Yano et al, ). DTH2 is a flowering activator under LD conditions, and both OsCOL4 and OsCOL10 are constitutive flowering repressors in rice (Lee et al, ; Tang et al, ; Wu et al, ). Interestingly, we identified homologs of Ghd7 and Ehd1 from CCT and RR families with LD predominant and SD predominant patterns, respectively (Figure ).…”

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

“…Ehd1 is up‐regulated by some proteins such as Ehd2/OsINDETERMINATE 1 (OsID1)/Rice INDETERMINATE 1 (RID1) (Matsubara et al ., ; Park et al ., ; Wu et al ., ), Ehd3 (Matsubara et al ., ), Ehd4 (Gao et al ., ), VERNALIZATION INSENSITIVE 3‐LIKE 2 (OsVIL2) (Wang et al ., ), SET domain group protein 724 (SDG724) (Sun et al ., ), OsMADS50 (Ryu et al ., ) and OsMADS51 (Kim et al ., ). In contrast, multiple proteins also act as negative regulators of Ehd1 , including Grain yield and heading date 7 (Ghd7) (Xue et al ., ), LEC2 and FUSCA3‐Like 1 (OsLFL1) (Peng et al ., ), CONSTANS‐Like 4 (OsCOL4) (Lee et al ., ), OsCOL10 (Tan et al ., ), OsCOL13 (Sheng et al ., ), Date To Heading on chromosome 7 (DTH7) (Gao et al ., ), DTH8 (Wei et al ., ), Heading date 16 (Hd16)/Early Flowering 1 (EL1) (Dai and Xue, ; Hori et al ., ), SUPERNUMERARY BRACT (SNB), OsINDETERMINATE SPIKELET 1 (OsIDS1) (Lee et al ., ), OsMADS56 (Ryu et al ., ), ABA responsive element binding factor 1 (OsABF1) (Zhang et al ., ) and Heme Activator Protein like 1 (OsHAPL1) (Zhu et al ., ). Heading date 1 (Hd1) also activates Ehd1 expression under SD, but functions as a repressor of Ehd1 through interaction with Ghd7 under LD (Nemoto et al ., ).…”

Overexpression of OsMYB1R1–VP64 fusion protein increases grain yield in rice by delaying flowering time

“…VP16 usually changed transcriptional repressors into activators, or enhanced transcriptional activation activity, leading to enhanced or opposite phenotypes compared to those produced by knockout mutations in Arabidopsis [56][57][58][59]. Recently, VP16 has been used in rice to investigate the function of TFs in determining flowering time [60,61]. Through its transcriptional activation motif VP16 greatly activates expression genes downstream from the TFs.…”

“…Recently, VP16 has been used in rice to investigate the function of TFs in determining flowering time [60,61]. Through its transcriptional activation motif VP16 greatly activates expression genes downstream from the TFs.…”