Critical sequence polymorphism across the gene and its flanking regions may reflect the evolutionary process of species adapting to different environments. GmFT2a has a recessive allele for delayed flowering, which contains a Ty1/ copia-like retrotransposon SORE-1 inserted in the first intron that attenuates GmFT2a expression by its allele-specific transcriptional repression. The promoter of GmFT2a in soybean has high polymorphism, and some SNPs in the promoter region are associated with flowering time and photoperiod sensitivity. Different natural variations of FT promoter sequences are confirmed responsible for diverse flowering time in Arabidopsis and also in rice. In plants, multiple regulation pathways regulate FT expression in response to diverse environmental signals, which enable flowering and other developmental responses to be seasonally timed. Currently, a new GmFT2c was recently found inserted in a putative transponson in the third intron, and GmFT2d was determined structurally rearranged with some remnant in the genome, indicating that GmFT2 subclades ( GmFT2a, GmFT2b, GmFT2c and Gm FT2d) have different evolutionary trajectories. In transgenic soybean overexpressing E1, GmFT1a and GmFT4 expression was up regulated, whereas the expression of GmFT2a and GmFT5a was suppressed. Ectopic expression experiments in Arabidopsis also demonstrated that other soybean FT family genes including GmFT2b, GmFT3a, GmFT3b and GmFT5b promoted flowering, whereas GmFT4 delayed flowering. GmFT2a and GmFT5a coordinately control flowering as flowering integrators and can be regulated by E1, E2, E3 and E4. Ten FT-like genes have been identified in soybean among which GmFT2a and GmFT5a are confirmed as flowering promoters whereas GmFT1a is divergent as a floral and maturity inhibitor. įT, which encodes a putative florigen, is a key integrator gene in the regulation of flowering in Arabidopsis, and the function is highly conserved in different species. Among the six loci, E9 has been confirmed as GmFT2a, an orthologue of the Arabidopsis Flowering Locus T ( FT) gene, which plays an important role in flowering. To date, six of these loci, E1, E2, E3, E4, E9 and J, have been cloned. They play different roles in flowering and maturity maintenance under diverse photoperiod patterns. A majority of these loci were reviewed by Xia et al. A total of 10 maturity loci are characterized in soybean, including E1- E10 and J.
Multiple genes control flowering time and maturity in soybean.
Previous research indicates that maturity diversity in soybean is attributed to the variation and combination of genes responding to photoperiod and temperature. MG0000, a new maturity group that matures the earliest to date was identified in some super-early varieties from high-latitude cold regions in China and the Far East of Russia. Gai divided 256 Chinese soybean landraces into 12 maturity groups without MGX. In North America, soybeans are classified into 13 maturity groups: MG000 to MGX in the ascending order of maturity. Soybeans are planted within a wide range of latitudes across the world resulting from the rich diversity of varieties in flowering time and maturity. This study will facilitate the understanding of the roles of FTs in flowering and maturity. Some natural variations exist within the 10 FT family genes, which might be involved in soybean adaptation to different environments and have an influence on diverse flowering time and maturity. Based on the association analysis, 38 polymorphic sites had a significant association with flowering time at the level of p < 0.01. Haplotype analysis showed that a total of 17 haplotypes had correlative relationships with flowering time and maturity among the 10 FT genes, namely, 1a-H3, 1b-H1, 1b-H6, 1b-H7, 2a-H1, 2a-H3, 2a-H4, 2a-H9, 2b-H3, 2b-H4, 2b-H6, 2b-H7, 3b-H4, 5a-H1, 5a-H2, 5a-H4 and 5b-H1. GmFT3b and GmFT5b might have experienced breeding selection in the process of soybean domestication and breeding. They were diversified at the genome sequence polymorphism level. Ten FT family genes, GmFT1a, GmFT1b, GmFT2a, GmFT2b, GmFT3a, GmFT3b, GmFT4, GmFT5a, GmFT5b and GmFT6, were cloned and sequenced in the 127 varieties evenly covering all 14 known maturity groups (MG0000-MGX). Therefore, we conducted this study to discover natural variations in FT family genes in association with flowering time and maturity. However, to date, the relations between natural variations of FT family genes and the diversity of flowering time and maturity in soybean are not clear. Flowering Locus T ( FT) family genes function as key flowering integrators, with flowering-promoting members GmFT2a/GmFT5a and flowering-inhibiting members GmFT4/ GmFT1a antagonistically regulating vegetative and reproductive growth. Flowering time and maturity are among the most important adaptive traits in soybean ( Glycine max (L.) Merill).