OsCO3, a CONSTANS-LIKE gene, controls flowering by negatively regulating the expression of FT-like genes under SD conditions in rice

Abstract

The photoperiod is an important environmental stress that determines flowering time. The CONSTANS (CO) and Heading date 1 (Hd1) genes are known to be central integrators of the photoperiod pathway in Arabidopsis and rice, respectively. Although they are both members of the CONSTANS-LIKE (COL) family and have two B-boxes and a CCT domain, rice also possesses novel COL genes that are not found in Arabidopsis. Here, we demonstrate that a novel COL gene, OsCO3, containing a single B-box and a CCT domain, modulates photoperiodic flowering in rice. The circadian expression pattern of OsCO3 mRNA oscillated in a different phase from Hd1 and was similar to that of OsCO3 pre-mRNA, suggesting that the diurnal expression pattern of OsCO3 transcripts may be regulated at the transcriptional level. Overexpression of OsCO3 specifically caused late flowering under short day (SD) conditions relative to wild-type rice plants. The expression of Hd3a and FTL decreased in these transgenic plants, whereas the expression of Hd1, Early heading date 1 (Ehd1), OsMADS51, and OsMADS50 did not significantly change. Our results suggest that OsCO3 primarily controls flowering time under SD conditions by negatively regulating Hd3a and FTL expression, independent of the SD-promotion pathway.

Photoperiodic control of flowering in barley

“…2. Kim et al (2008) reported that OsB inhibits flowering under SD conditions in rice without the mediation of Hd1 or Ehd1. These data show that HvCO2 and HvCO3 are likely also to be involved in flowering.…”

Characterization of a <i>CONSTANS-like</i> Gene from Pigeon Orchid (<i>Dendrobium crumenatum</i> Swartz) and its Expression under Different Photoperiod Conditions

“…Both of these proteins have a function in induction of flowering, but their regulation pathways are different. Hd1 was demonstrated to promote flowering in short day (SD) (Hayama et al, 2003;Kim et al, 2008). While AtCO promotes flowering in long day (LD) (Putterill et al, 1995;Samach et al, 2000;Zhang et al, 2011).…”

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

“…Hwaan background) were grown in a growth chamber at 28°C under either short-day (SD) conditions [10/14 h (light/dark)] or long day (LD) conditions [14.5/9.5 h (light/dark)] with light supplied at an intensity of 100 µmol m -2 s -1 , as described in Kim et al 2008. For growth under SD conditions, rice plants were first grown in LD conditions for 20 days and then transferred to SD conditions until flowering.…”

“…For growth under SD conditions, rice plants were first grown in LD conditions for 20 days and then transferred to SD conditions until flowering. The flowering time was measured as the days to heading (DTH), which is the number of days from planting in pots to the emergence of the first panicle from the flag leaf sheath, as described previously (Kim et al 2008). …”

“…The protein concentration was determined using the Bradford solution (Bio-Rad, Hercules, CA). Subsequently, proteins were separated by SDS-PAGE onto a 12.5% gel, transferred onto polyvinylidene difluoride (PVDF) membrane (Bio-Rad), and detected by western blot, as described previously (Kim et al 2008). …”