Flowering Date1, a major photoperiod sensitivity gene in adzuki bean, is a soybean floral repressor E1 ortholog.

Yusuke Imoto,Takumi Iida,Masahiko Mori,Shuichi Matsuda,Yuki Horiuchi,Taisei Oka,Shoko Yoshikawa,Yoshihiko Tokuji,Kiyoaki Kato

doi:10.1270/jsbbs.21051

Abstract

Adzuki bean is an important legume crop originating in temperate regions, with photoperiod in sensitivity being a key factor in its latitudinal adaptation. The Flowering Date1 (FD1) gene has a large effect on the photoperiodic response of flowering time, but the molecular basis for the effect of this locus is undetermined. The present study delimited the FD1 locus to a 17.1 kb sequence, containing a single gene, an E1 ortholog (VaE1). A comparison between Vigna angularis ‘Shumari’ (photoperiod insensitive) and ‘Acc2265’ (photoperiod sensitive) identified 29 insertions/deletions and 178 SNPs upstream of VaE1 in the FD1 locus. VaE1 expression in ‘Acc2265’ was greater under long-day than short-day conditions, whereas VaE1 expression in ‘Shumari’ was lower regardless of day length. These findings suggested that responsible gene of FD1 is a VaE1, which acts as a floral repressor by being upregulated in response to long-day conditions. The inability to upregulate VaE1 under long-day conditions was linked to its ability to flower under these conditions. These results provide greater understanding of the molecular control of a flowering date and clues enabling the breeding of adzuki bean at higher latitudes.

Highlights

The adzuki bean, Vigna angularis (Willd.) Ohwi and Ohashi, is a traditional legume grown throughout East Asia and northern South Asia (Lumpkin and McClary 1994, Zong et al 2003)
Late and early flowering individuals fit the 3:1 Mendelian segregation ratio (χ2(3:1) = 2.92, p = 0.09). These results indi‐ cated that the early flowering phenotype is controlled by a recessive Flowering Date1 (FD1) allele
Seventy recombinant F2 individuals were selected and their genotypes at FD1 were evaluated based on the segregation patterns of initial flowering date in the F3 progeny

Summary

Introduction

The adzuki bean, Vigna angularis (Willd.) Ohwi and Ohashi, is a traditional legume grown throughout East Asia and northern South Asia (Lumpkin and McClary 1994, Zong et al 2003). In Japan, adzuki beans are the second most important legume after soybeans, with about 90% of adzuki beans grown in Hokkaido prefecture, the northern‐ most island in Japan (NL45-42°). In Hokkaido, adzuki beans are planted in late May and harvested in midSeptember to early October, avoiding damage at low temperatures. Soybean [Glycine max (L.) Merr.] is an important model short-day legume plant used to assess photoperiodism (Owen 1927). The E1 gene is thought to have the greatest effect on determination of flowering time under field conditions, delaying plant maturity (Xia et al 2012). E1 is a putative transcription factor that negatively controls two florigen genes, GmFT2a and GmFT5a, to delay flowering under a background that includes with functional PHYA

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Conclusion