Abstract
AbstractPrecise regulation of flowering time is critical for cereal crops to synchronize reproductive development with optimum environmental conditions, thereby maximizing grain yield. The plant specific geneGIGANTEA(GI) plays an important role in the control of flowering time, with additional functions on the circadian clock and plant stress responses. In this study, we show thatGIloss-of-function mutants in a photoperiod sensitive tetraploid wheat background exhibit significant delays in heading time under both long-day (LD) and short-day (SD) photoperiods, with stronger effects under LD. However, this interaction between GI and photoperiod is no longer observed in isogenic lines carrying either a photoperiod insensitive allele in thePHOTOPERIOD1(PPD1) gene or a loss-of-function allele inEARLY FLOWERING 3(ELF3), a known repressor ofPPD1.These results suggest that the normal circadian regulation ofPPD1is required for the differential effect ofGIon heading time in different photoperiods. Using crosses between mutants or transgenic ofGIand those of critical genes in the flowering regulation pathway, we show thatGIaccelerates wheat heading time by promotingFLOWERING LOCUS T1(FT1) expression via interactions withELF3, VERNALIZATION 2(VRN2),CONSTANS(CO), and the age-dependent microRNA172-APETALA2(AP2) pathway, at both transcriptional and protein levels. Our study reveals conservedGImechanisms between wheat and Arabidopsis, but also identifies specific interactions of GI with the distinctive photoperiod and vernalization pathways of the temperate grasses. These results provide valuable knowledge for modulating wheat heading time and engineering new varieties better adapted to a changing environment.
Publisher
Cold Spring Harbor Laboratory