Genetic control of flowering time in legumes

Abstract

The timing of flowering, and in particular the degree to which it is responsive to the environment, is a key factor in the adaptation of a given species to various ecogeographic locations and agricultural practices. Flowering time variation has been documented in many crop legumes, and selection for specific variants has permitted significant expansion and improvement in cultivation, from prehistoric times to the present day. Recent advances in legume genomics have accelerated the process of gene identification and functional analysis, and opened up new prospects for a molecular understanding of flowering time adaptation in this important crop group. Within the legumes, two species have been prominent in flowering time studies; the vernalization-responsive long-day species pea (Pisum sativum) and the warm-season short-day plant soybean (Glycine max). Analysis of flowering in these species is now being complemented by reverse genetics capabilities in the model legumes Medicago truncatula and Lotus japonicus, and the emergence of genome-scale resources in a range of other legumes. This review will outline the insights gained from detailed forward genetic analysis of flowering time in pea and soybean, highlighting the importance of light perception, the circadian clock and the FT family of flowering integrators. It discusses the current state of knowledge on genetic mechanisms for photoperiod and vernalization response, and concludes with a broader discussion of flowering time adaptation across legumes generally.

Rapid establishment of a flowering cline in Medicago polymorpha after invasion of North America

“…Flowering time is a model trait for understanding the genetics of clinal adaptation (Mouradov, Cremer, & Coupland, 2002;Pineiro & Coupland, 1998;Weller & Ortega, 2015), and the evolution of clines Caicedo, Stinchcombe, Olsen, Schmitt, & Purugganan, 2004;Samis, Heath, & Stinchcombe, 2008;Stinchcombe et al, 2004) and invaded range (Samis et al, 2012). In the model legume, Medicago truncatula, a dozen genes from several pathways involved in floral development are associated with clinal variation in flowering time (Burgarella et al, 2016).…”

Gene networks underlying faster flowering induction in response to far-red light

“…In our experiment, at the first time-point (TP1) under FR-enriched light, we found a gene-coding protein (TSub_g12538) homologous of a pea FTb2 whose relative expression was also higher under FR compared to B-enriched lights. This protein is expressed specifically in pea and Medicago leaves under long days and meets the characteristics of the classical ‘florigen’ (Weller & Ortega 2015). The differential expression of this homologous gene may suggest its role as a floral promoter in subterranean clover.…”

“…The floral promoter CO protein is up-regulated by long-day growing conditions and its expression is stabilised by FR light through PHYTOCHROME A activity (Kim et al 2008; Pin & Nilsson 2012; Song et al 2013). In Medicago, a temperate legume as subterranean clover, it has been suggested that the integration of responses to day length and light quality may not be regulated by CO -like ( COL ) genes (Wong et al 2014; Weller & Ortega 2015). In contrast, in subterranean clover, we identified the expression of a CCT motif ( TSub_g7401 ) at an early developmental stage (TP1) under FR-enriched light.…”

“…Merr. ), Medicago and Lotus japonicus , no legume species has yet emerged as a predominant model in the study of flowering time (Weller & Ortega 2015). Recently, we established subterranean clover ( Trifolium subterraneum L.) as a reference species for genetic and genomic studies within the genus Trifolium .…”

“…In legumes, the basic genes and gene families central to pathways controlling flowering time in arabidopsis appear to be largely conserved. However, there are numerous examples of gene duplication and loss (Weller & Ortega 2015). In pea, the conserved role of the arabidopsis genes GI, EARLY FLOWERING 3 and EARLY FLOWERING 4 in the regulation of FT genes has been demonstrated (Hecht et al 2007; Liew et al 2009; Weller et al 2012).…”