Cloning And Functional Analysis For Quantitative Trait Locus Of Photoperiod Regulated Flowering In Soybean [Glycine Max(L.) Merr.]

Soybean [Glycine Max(L.) Merr.] is an important economic crop providing oil and protein for food source. Flowering time and maturity greatly affect soybean yield and its production. Understanding the molecular mechnisms underlying flowering time and maturity will facilitate the molecular breeding towards high yield. In this research, we identified QTLs(Quantative trait locus) associated with flowering time, cloned the candidate genes and characterized their functions. The findings in this study will provide theoretical molecular basis and valuble tools for molecular breeding in soybean.On the basis of the recombinant inbred lines(RILs) derived from the cross of TK780 and H4, we cloned the candidate genes FL1 and FL2 for q FT-B1 and q FT-H, respectively, by the whole genome resequencing and bioinformatics analysis under the background of E1 allele. Compared with H4, TK780 showed one base deletion for FL1 and one base substitution for FL2, which resulted in the TK780 had no CCT motif. By genetic transformation, we verified both of them controled late flowering trait. In addition, we also demonstrated both of them located in nucles and E1, E2, E3 and E4 regulated FL1 and FL2 on transcriptional level and both of them were regulated by circadian clock.On the basis of F2 populations derived from the cross between Harosory and BR121, we detected one QTL, q FT-C1, associated with flowering time. By blasting with genes of Arabidopisis thaliana, we found one candidate gene Gm ELF3 and cloned it from in parent lines. Compared with Harosory, BR121 had 10 bp deltetion, which resulted BR121 lost three conserved regions. We also demonstrated that Gm ELF3 was J gene by cloned the different cultivars associated with long-junveile trait and genetic transformation. J could form complex with Gm ELF4 and Gm LUX. Finally, E1, E2, E3 and E4 through different mechanisms to control J under long-day and short-day photoperiod.In addition, a population of 91 recombinant inbred lines(RILs) derived from a cross between AGS292 and K3 was used for map construction and QTL analysis. The map covered 2546.7 c M and included 52 new promoter-specific indel(PSI) and 9 new exon-specific indel(ESI) markers. For four SD environments, seven QTLs were detected. Five of them were associated with the long juvenile trait. Under the five LD environments, as expected, q FT-O for the E2 locus and q FT-L for the E3 locus were identified, suggesting that E2 and E3 loci are very important for soybean adaptation in LD photoperiod. Conjoint analysis of multiple environments identified nine additive QTLs and nine pairs of epistatic QTLs, among which most were involved in interactions with the environments. In total, five QTLs(q FT-B2-1, q FT-C1-1, q FT-K, q FT-D2 and q FT-F) were identified that may represent novel flowering time genes. The QTLs detected in our research is helpful to enrich the genetic mechanism of flowering time for soybean.In conclusion, the innovation was that, based on the QTL, we not only first cloned the J gene, which was the first one that promoted the flowering time under SD environment in soybean, but also the FL1 and FL2, which were the homologous genes of PRR37 for circadian clock. The results also showed that they parted in the genetic network including E1, E2, E3 and E4 for flowering time. The genetic transformation results demonstrated they influenced flowering tim in soybean. The results are helpful to further understand the molecular mechanism and will provide a fundamental foundation for future studies of flowering time in soybean.