Natural Variations Of FT Family Genes In Soybean Varieties Covering A Wide Range Of Maturity Groups

Maturity is one of the most important adaptive traits in soybean(Glycine max(L.) Merill), controlled by multiple genes. Molecular biology research suggested maturity diversity in soybean was attributed to variation of relevant genes responding to photoperiod and temperature and their variation combination. FT is a key flowering integrating gene encoding florigen in plants. 10 FT genes have been identified in soybean. Among them, Gm FT2 a and Gm FT5 a have been regarded as the candidate genes of florigen, which exert a vital role in inducing and maintaining flowering. However, now it is not clear about natural variations of FT family genes and the relation between the former and flowering date and maturity in soybean. In this study, we selected 127 soybean varieties covering 14 maturity groups from MG0000 to MGX, with a continuous distribution in maturity group. These varieties were planted in pots under natural day and we investigated their emergence(Ve), their beginning of bloom(R1), their beginning of maturity(R7) and their fully maturity(R8). The 10 FT family genes across the entire gene region were then cloned and sequenced, including Gm FT1 a, Gm FT1 b, Gm FT2 a, Gm FT2 b, Gm FT3 a, Gm FT3 b, Gm FT4, Gm FT5 a, Gm FT5 b and Gm FT6, analysing their sequence polymorphisms and haplotypes. Main results were as follows:1. These varieties varied greatly in flowering date and maturity date and had high diversity.2. Sequence polymorphism of 10 soybean FT family genes along the entire gene region showed obvious difference, of which Gm FT1 a and Gm FT1 b had high polymorphism, in contrast to conserved sequence about Gm FT3 a and Gm FT4. In coding region, Gm FT4 was highly conserved, Gm FT3 a, Gm FT5 a and Gm FT5 b were relatively conserved. Gm FT3 b and Gm FT5b’s Tajima’s D values were all positive, being far away from zero significantly, and their polymorphic sites had high proportion of strong LD. These indicated they might have experienced relevant selection in the process of natural selection and domestication. Protein sequecnes had comparatively consistent coservation which of FT family genes had closer phylogenetic relationships.3. Some haplotypes of Gm FT1 a, Gm FT1 b, Gm FT2 a, Gm FT2 b, Gm FT3 b, Gm FT5 a and Gm FT5 b showed correlative relationships with flowering date and maturity, but Gm FT3 a, Gm FT4 and Gm FT6 didn’t have any apparent connections.4. There existed some associations between soybean FT family genes’ haplotypes, that was, Gm FT1a-Hap4 always appeared in these varieties which were Gm FT1b-Hap1, with their maturity groups blonging to these varieties including MGI and after MGI, being Gm FT1a-P2, Gm FT1a-P3 and Gm FT1b-P1; Gm FT2a-Hap1 and Gm FT2a-Hap3 appeared in these varieties of Gm FT2b-Hap6 and Gm FT2b-Hap7, with their maturity groups belonging to these varieties including MG0 and after MG0, being Gm FT2a-P1 of Gm FT2a-Hap3 and Gm FT2b-P1 of Gm FT2b-Hap6 and Gm FT2b-Hap7; Gm FT3b-Hap3 appeared in these varieties which were Gm FT5b-Hap1, with their maturity groups blonging to these varieties including MGVI and before MGVI, being Gm FT5a-P0 of Gm FT5b-Hap1.FT family genes exist some natural variations, which may involve soybean to adapt to different environment and have an influence on diverse flowering date and maturity.