AUTHOR=Chen Liting , Yan Yuanyuan , Ke Huifeng , Zhang Zihao , Meng Chengsheng , Ma Limei , Sun Zhengwen , Chen Bin , Liu Zhengwen , Wang Guoning , Yang Jun , Wu Jinhua , Li Zhikun , Wu Liqiang , Zhang Guiyin , Zhang Yan , Wang Xingfen , Ma Zhiying 

TITLE=SEP-like genes of Gossypium hirsutum promote flowering via targeting different loci in a concentration-dependent manner

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.990221

DOI=10.3389/fpls.2022.990221

ISSN=1664-462X

ABSTRACT=<p><italic>SEP</italic> genes are famous for their function in the morphological novelty of bisexual flowers. Although the diverse functions of <italic>SEP</italic> genes were reported, only the regulatory mechanisms underlying floral organ development have been addressed. In this study, we identified <italic>SEP</italic>-like genes in <italic>Gossypium</italic> and found that <italic>SEP3</italic> genes were duplicated in diploid cotton varieties. <italic>GhSEP4.1</italic> and <italic>GhSEP4.2</italic> were abundantly transcribed in the shoot apical meristem (SAM), but only <italic>GhSEP4.2</italic> was expressed in the leaf vasculature. The expression pattern of <italic>GhSEP</italic>s in floral organs was conserved with that of homologs in <italic>Arabidopsis</italic>, except for <italic>GhSEP2</italic> that was preponderantly expressed in ovules and fibers. The overexpression and silencing of each single <italic>GhSEP</italic> gene suggested their distinct role in promoting flowering <italic>via</italic> direct binding to <italic>GhAP1</italic> and <italic>GhLFY</italic> genomic regions. The curly leaf and floral defects in overexpression lines with a higher expression of <italic>GhSEP</italic> genes revealed the concentration-dependent target gene regulation of GhSEP proteins. Moreover, GhSEP proteins were able to dimerize and interact with flowering time regulators. Together, our results suggest the dominant role of <italic>GhSEP4.2</italic> in leaves to promote flowering <italic>via GhAP1-A04</italic>, and differently accumulated GhSEP proteins in the SAM alternately participate in forming the dynamic tetramer complexes to target at the different loci of <italic>GhAP1</italic> and <italic>GhLFY</italic> to maintain reproductive growth. The regulatory roles of cotton <italic>SEP</italic> genes reveal their conserved and diversified functions.</p>