AUTHOR=Lee Su Hyeon , Choi Cheol Woo , Park Kyoung Mi , Jung Wook-Hun , Chun Hyun Jin , Baek Dongwon , Cho Hyun Min , Jin Byung Jun , Park Mi Suk , No Dong Hyeon , Lim Lack Hyeon , Shim Sang In , Chung Jong Il , Kim Min Chul 

TITLE=Diversification in Functions and Expressions of Soybean FLOWERING LOCUS T Genes Fine-Tunes Seasonal Flowering

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.613675

DOI=10.3389/fpls.2021.613675

ISSN=1664-462X

ABSTRACT=<p>The proper timing of flowering in response to environmental changes is critical for ensuring crop yields. <italic>FLOWERING LOCUS T</italic> (<italic>FT</italic>) 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 <italic>FT</italic> homologs. Overexpression of <italic>GmFT</italic> homologs in <italic>Arabidopsis</italic> revealed that a set of <italic>GmFT</italic> homologs, including <italic>GmFT2a/2b</italic>, <italic>GmFT3a/3b</italic>, and <italic>GmFT5a/5b</italic>, promoted flowering similar to <italic>FT</italic>; in contrast, <italic>GmFT1a/1b</italic>, <italic>GmFT4</italic>, and <italic>GmFT6</italic> delayed flowering. Consistently, expressions of <italic>GmFT2a</italic>, <italic>GmFT2b</italic>, and <italic>GmFT5a</italic> were induced in soybean leaves in response to floral inductive short days, whereas expressions of <italic>GmFT1a</italic> and <italic>GmFT4</italic> were induced in response to long days. Exon swapping analysis between floral activator <italic>GmFT2a</italic> and floral repressor <italic>GmFT4</italic> revealed that the segment B region in the fourth exon is critical for their antagonistic functions. Finally, expression analysis of <italic>GmFT2a</italic>, <italic>GmFT5a</italic>, and <italic>GmFT4</italic> in soybean accessions exhibiting various flowering times indicated that the mRNA levels of <italic>GmFT2a</italic> and <italic>GmFT5a</italic> were higher in early flowering accessions than in late-flowering accessions, while <italic>GmFT4</italic> showed the opposite pattern. Moreover, the relative mRNA levels between <italic>GmFT2a</italic>/<italic>GmFT5a</italic> and <italic>GmFT4</italic> was important in determining day length-dependent flowering in soybean accessions. Taken together, our results suggest that the functions of <italic>GmFT</italic> 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 <italic>GmFT</italic> homologs.</p>