Ectopic expression of OsMADS45 activates the upstream genes Hd3a and RFT1 at an early development stage causing early flowering in rice

Abstract

BackgroundThe rice gene, OsMADS45, which belongs to the MADS-box E class gene, participates in the regulation of floral development. Previous studies have revealed that ectopic expression of OsMADS45 induces early flowering and influences reduced plant height under short-day (SD) conditions. However, the regulation mechanism of OsMADS45 overexpression remains unknown. We introduce an OsMADS45 overexpression construct Ubi:OsMADS45 into TNG67 plants (an Hd1 (Heading date 1) and Ehd1 (Early heading date 1) defective rice cultivar grown in Taiwan), and we analyzed the expression patterns of various floral regulators to understand the regulation pathways affected by OsMADS45 expression.ResultsThe transgenic rice exhibit a heading date approximately 40 days earlier than that observed in TNG67 plants, and transgenic rice display small plant size and low grain yield. OsMADS45 overexpression did not alter the oscillating rhythm of the examined floral regulatory genes but advanced (by approximately 20 days) the up-regulate of two florigens, Hd3a (Heading Date 3a) and RFT1 (RICE FLOWERING LOCUS T1) and suppressed the expression of Hd1 at the juvenile stage. The expression levels of OsMADS14 and OsMADS18, which are two well-known reproductive phase transition markers, were also increased at early developmental stages and are believed to be the major regulators responsible for early flowering in OsMADS45-overexpressing transgenic rice. OsMADS45 overexpression did not influence other floral regulator genes upstream of Hd1 and Ehd1, such as OsGI (OsGIGANTEA), Ehd2/Osld1/RID1 and OsMADS50.ConclusionThese results indicate that in transgenic rice, OsMADS45 overexpressing ectopically activates the upstream genes Hd3a and RFT1 at early development stage and up-regulates the expression of OsMADS14 and OsMADS18, which induces early flowering.Electronic supplementary materialThe online version of this article (doi:10.1186/1999-3110-54-12) contains supplementary material, which is available to authorized users.

Expression of sugarcane genes associated with perception of photoperiod and floral induction reveals cycling over a 24-hour period

“…Expression of ShFT-A in the spindle leaf peaked at the onset of the light period, however this peak was not observed in other leaf types and expression was minimal at all time points in the mature leaf (Figs 5h, 6e). The expression profile of ShFT-A, over a 24-h cycle, was similar to FT profiles reported in rice (known as Hd3A and RFT1; Komiya et al 2008;Zhao et al 2012;Wang et al 2013;Lee and An 2015) and sorghum (known as CENTRORADIALES, CN; Yang et al 2014). In rice the expression peak of Hd3a and RFT1 was at the transition from dark to light in both photoperiod inductive and non-inductive conditions, however there was a higher level of expression under the inductive conditions (Izawa et al 2002;Lee et al 2016;Sun et al 2016).…”

“…6c). The 24-h cycle expression pattern of ShGI in the TVD leaf is similar to the pattern seen in a Brazilian sugarcane cultivar (Hotta et al 2013) and also to homologues in rice (Hori et al 2013;Wang et al 2013;Lee and An 2015) and soybean (Izawa et al 2011;Li et al 2013;Wang et al 2013;Lee and An 2015). In rice and soybean, grown under floral induction conditions, the peak expression of GI was maintained at the transition from the light to dark period, but this is now occurring earlier in the 24-h cycle (expression has contracted with the short daylength), and in rice, expression was increased by~25% (Filichkin et al 2011;Hori et al 2013;Li et al 2013).…”

“…5a, f, g). In northern blots the rice AP1 homologue, OsMADS14, appears to have consistent expression over 24 h similar to the ShAP1 expression (Wang et al 2013). In Arabidopsis, TF1 expression peaked at the transition from light to dark periods under LD conditions, along with an increase in expression over that reported in SD conditions (Sanchez et al 2011).…”

Ectopic expression of Arabidopsis FD and FD PARALOGUE in rice results in dwarfism with size reduction of spikelets

“…TNG67, a photoperiod insensitive flowering rice cultivar containing defective Hd1 and Ehd1 sequences the same as those of Taichung65 (T65)4546 was used to produce transgenic rice plants and the transgenic plants were grown in a growth chamber (14 h L, 28 °C/10 h D, 26 °C) for 2 weeks after germination and moved to the outdoor GMO greenhouse of the Academia Sinica Biotechnology Center in Southern Taiwan (23°04′N 120°17′E). Phenotypes of transgenic rice were examined from the second crop period (July to November) of 2011 to the first crop period (February to June) 2016.…”

Reversion of the photoperiod dependence of flowering in rice with synthetic Hd1-microProteins

“…Hd1's role in flowering is clearly observed in knockout and overexpressor plants of Hd1 which show early and late flowering phenotype respectively in comparison to WT in LD conditions (Gómez-Ariza et al, 2015;R. Ishikawa et al, 2011;Izawa et al, 2002;Takahashi, Teshima, Yokoi, Innan, & Shimamoto, 2009;Wang et al, 2013;Yano et al, 2000;Zhang et al, 2016).…”