title: A pair of floral regulators sets critical day length for Hd3a florigen expression in rice.
abstract: The critical day length triggering photoperiodic flowering is set as an acute, accurate threshold in many short-day plants, including rice. Here, we show that, unlike the Arabidopsis florigen gene FT, the rice florigen gene Hd3a (Heading date 3a) is toggled by only a 30-min day-length reduction. Hd3a expression is induced by Ehd1 (Early heading date 1) expression when blue light coincides with the morning phase set by OsGIGANTEA(OsGI)-dependent circadian clocks. Ehd1 expression is repressed by both night breaks under short-day conditions and morning light signals under long-day conditions. Ghd7 (Grain number, plant height and heading date 7) was acutely induced when phytochrome signals coincided with a photosensitive phase set differently by distinct photoperiods and this induction repressed Ehd1 the next morning. Thus, two distinct gating mechanisms--of the floral promoter Ehd1 and the floral repressor Ghd7--could enable manipulation of slight differences in day length to control Hd3a transcription with a critical day-length threshold.
authors.affiliation: Photosynthesis and Photobiology Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Japan.
authors.forename: Hironori
authors.initials: H
authors.lastname: Itoh
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Nonoue
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yano
authors.forename: Takeshi
authors.initials: T
authors.lastname: Izawa
mesh_terms: D002940:Circadian Rhythm; D035264:Flowers / Q000235:genetics* / Q000254:growth & development; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D015151:Immunoblotting; D012275:Oryza / Q000235:genetics* / Q000254:growth & development; D017440:Photoperiod; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger