The Soybean-Specific Maturity Gene E1 Family of Floral Repressors Controls Night-Break Responses through Down-Regulation of FLOWERING LOCUS T Orthologs  

Abstract

Photoperiodism is a rhythmic change of sensitivity to light, which helps plants to adjust flowering time according to seasonal changes in daylength and to adapt to growing conditions at various latitudes. To reveal the molecular basis of photoperiodism in soybean (Glycine max), a facultative short-day plant, we analyzed the transcriptional profiles of the maturity gene E1 family and two FLOWERING LOCUS T (FT) orthologs (FT2a and FT5a). E1, a repressor for FT2a and FT5a, and its two homologs, E1-like-a (E1La) and E1Lb, exhibited two peaks of expression in long days. Using two different approaches (experiments with transition between light and dark phases and night-break experiments), we revealed that the E1 family genes were expressed only during light periods and that their induction after dawn in long days required a period of light before dusk the previous day. In the cultivar Toyomusume, which lacks the E1 gene, virus-induced silencing of E1La and E1Lb up-regulated the expression of FT2a and FT5a and led to early flowering. Therefore, E1, E1La, and E1Lb function similarly in flowering. Regulation of E1 and E1L expression by light was under the control of E3 and E4, which encode phytochrome A proteins. Our data suggest that phytochrome A-mediated transcriptional induction of E1 and its homologs by light plays a critical role in photoperiodic induction of flowering in soybean.

The loss of vernalization requirement in narrow‐leafed lupin is associated with a deletion in the promoter and de‐repressed expression of a Flowering Locus T (FT) homologue

“…However, genes in the FTb clade are clearly lacking in L. angustifolius , suggesting that these genes do not play an essential evolutionary role in legume photoperiod responses, and raising the question of which FT genes may mediate the photoperiod response in this species. In soybean, two genes in the FTa3 and FTc clades ( FT2a and FT5a ) (Kong et al ., ; Xu et al ., ) have prominent roles in induction of flowering by photoperiod, and our analysis of the lupin genome suggests that a minimum complement of FTa3 and FTc genes may be sufficient for both vernalization and photoperiod responsiveness. It will be interesting in future to examine which lupin FT gene(s) may be regulated by photoperiod.…”

QTL Mapping for Drought-Responsive Agronomic Traits Associated with Physiology, Phenology, and Yield in an Andean Intra-Gene Pool Common Bean Population

“…Stable QTL for days to flowering and putative QTL for days to pod-setting were overlapped and co-localized on linkage group Pv01 (closest markers ATA3 and BMb1024), suggesting pleiotropy for genes controlling these highly correlated traits. In soybean, such a gene involved in both maturation and induction of flowering (E1 and its homologues) has been reported [54]. The overall numbers of detected QTLs for phenological traits were higher in the season of 2014, which might be associated with observed difference in timing of flowering and maturation with regard to watering conditions.…”

Assessment of Soybean Flowering and Seed Maturation Time in Different Latitude Regions of Kazakhstan

“…The E series of genes were shown to be important factors for plant adaptation in soybean growing regions [12], [14]. It was recently hypothesized that three of those E genes ( E1 , E3 , and E4 ) play larger roles in pre- and post-flowering photoperiod responses [11].…”

“…It was shown that E1-E4 genes are involved in regulation of both pre-flowering and post-flowering growth of plants under different photoperiod length [11]. E1 is a flowering repressor and encodes a transcription factor that contains a putative nuclear localization signal and region related to the B3 DNA-binding domain [7], [12]. E2 is an orthologue of the Arabidopsis flowering gene GIGANTEA [2], [13].…”