Abstract
The proper timing of flowering in response to environmental changes is critical for ensuring crop yields. FLOWERING LOCUS T (FT) homologs of the phosphatidylethanolamine-binding protein family play important roles as floral integrators in many crops. In soybean, we identified 17 genes of this family, and characterized biological functions in flowering for ten FT homologs. Overexpression of GmFT homologs in Arabidopsis revealed that a set of GmFT homologs, including GmFT2a/2b, GmFT3a/3b, and GmFT5a/5b, promoted flowering similar to FT; in contrast, GmFT1a/1b, GmFT4, and GmFT6 delayed flowering. Consistently, expressions of GmFT2a, GmFT2b, and GmFT5a were induced in soybean leaves in response to floral inductive short days, whereas expressions of GmFT1a and GmFT4 were induced in response to long days. Exon swapping analysis between floral activator GmFT2a and floral repressor GmFT4 revealed that the segment B region in the fourth exon is critical for their antagonistic functions. Finally, expression analysis of GmFT2a, GmFT5a, and GmFT4 in soybean accessions exhibiting various flowering times indicated that the mRNA levels of GmFT2a and GmFT5a were higher in early flowering accessions than in late-flowering accessions, while GmFT4 showed the opposite pattern. Moreover, the relative mRNA levels between GmFT2a/GmFT5a and GmFT4 was important in determining day length-dependent flowering in soybean accessions. Taken together, our results suggest that the functions of GmFT homologs have diversified into floral activators and floral repressors during soybean evolution, and the timing of flowering in response to changing day length is determined by modulating the activities of antagonistic GmFT homologs.
Highlights
Plants can sense seasonal changes, such as photoperiod and ambient temperature, and modulate their growth and development
RNA was extracted from soybean plants grown in green house conditions, and these gene-specific primers were used to amplify the full-length cDNAs obtained by reversetranscription (RT)-PCR
Phylogenetic analysis and alignment of amino acid sequences of Arabidopsis and soybean phosphatidylethanolamine-binding proteins (PEBPs) family members indicated that these 17 soybean orthologs fall into four different clades: the FLOWERING LOCUS T (FT), BFT, TERMINAL FLOWER 1 (TFL1), and MFT clades (Figure 1B and Supplementary Figure 1)
Summary
Plants can sense seasonal changes, such as photoperiod and ambient temperature, and modulate their growth and development . This is especially important in crops, where the decision of the proper time for transition from vegetative to reproductive phases in response to changing environments is crucial to their adaptability to agricultural habitats and productivity. 11 major genes, E1 through E10 and J, have been identified as being involved in the control of flowering and maturity in soybean (Watanabe et al, 2012; Kong et al, 2014; Samanfar et al, 2017). E6, E9, and J promote flowering and maturity, whereas the other genes delay flowering
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