Clock-Controlled and FLOWERING LOCUS T (FT)-Dependent Photoperiodic Pathway in Lotus japonicus I: Verification of the Flowering-Associated Function of an FT Homolog

Abstract

During the last decade, significant research progress in the study of Arabidopsis thaliana has been made in defining the molecular mechanism by which the plant circadian clock regulates flowering time in response to changes in photoperiod. It is generally accepted that the clock-controlled CONSTANS (CO)-FLOWERING LOCUS T (FT)-mediated external coincidence mechanism underlying the photoperiodic control of flowering time is conserved in higher plants, including A. thaliana and Oryza sativa. However, it is also assumed that the mechanism differs considerably in detail among species. Here we characterized the clock-controlled CO-FT pathway in Lotus japonicus (a model legume) in comparison with that of A. thaliana. L. japonicus has at least one FT orthologous gene (named LjFTa), which is induced specifically in long-days and complements the mutational lesion of the A. thaliana FT gene. However, it was speculated that this legume might lack the upstream positive regulator CO. By employing L. japonicus phyB mutant plants, we showed that the photoreceptor mutant displays a phenotype of early flowering due to enhanced expression of LjFTa, suggesting that LjFTa is invovled in the promotion of flowering in L. japonicus. These results are discussed in the context of current knowledge of the flowering in crop legumes such as soybean and garden pea.

Isolation and functional analysis of CONSTANS-LIKE genes suggests that a central role for CONSTANS in flowering time control is not evolutionarily conserved in Medicago truncatula

“…This may also be more generally true across the temperate legumes, at least for COLa , as COLa orthologs in pea and Lotus japonicus also do not show characteristic regulatory features of Arabidopsis CO (Hecht et al, 2007; Yamashino et al, 2013). Instead, CO -independent pathways may have a more prominent role in this plant group.…”

The Micro-RNA172c-APETALA2-1 Node as a Key Regulator of the Common Bean-Rhizobium etli Nitrogen Fixation Symbiosis

“…Besides conserved roles, specialized/particular species-specific functions of miR172, such as the induction of tuberization in potato (Solanum tuberosum), have been reported (Martin et al, 2009). In legumes, conserved roles of the miR172 node have been documented for L. japonicus (control of flowering time; Yamashino et al, 2013) and soybean (control of juvenile-to-adult phase transition; Yoshikawa et al, 2013). In addition, the control of nodulation during the rhizobia symbiosis has been proposed as a family-specific acquired function of miR172 in different legumes and has been demonstrated for soybean (Yan et al, 2013;Wang et al, 2014).…”

The Chickpea Early Flowering 1 (Efl1) Locus Is an Ortholog of Arabidopsis ELF3

“…This gene family has been studied in several legume species (Kong et al, 2010;Hecht et al, 2011;Laurie et al, 2011;Yamashino et al, 2013;Zhai et al, 2014), where most species have at least five FT-like genes that may be divided into three distinct clades: FTa, FTb, and FTc . We identified five members of this family in chickpea and observed clear differences in their expression between ICCV 96029 and CDC Frontier.…”