Recently, the research entitled “GhGRF4/GhARF2-GhGASA24 module regulates fiber cell wall thickness by modulating cellulose biosynthesis in upland cotton (Gossypium hirsutum)” has been published by  The Plant Journal (IF = 7.1). The researchers identified a major gene that controls the elongation of upland cotton fibers, and analyzed the relevant regulatory mechanisms, which provides theoretical support for improving the quality of cotton fibers, especially textile-related indicators.

Cotton fiber ( Gossypium hirsutum ) serves as an ideal model for investigating the molecular mechanisms of plant cell elongation at the single-cell level. Brassinosteroids (BRs) play a crucial role in regulating plant growth and development. However, the mechanism by which BR influences cotton fiber elongation remains incompletely understood. In this study, we identified  EXORDIUM-like  ( GhEXL3 ) through transcriptome analysis of fibers from BR-deficient cotton mutant  pagoda 1  ( pag1 ) and  BRI1-EMS-SUPPRESSOR 1  ( GhBES1.4 , encoding a central transcription factor of BR signaling) overexpression cotton lines. Knockout of  GhEXL3  using CRISPR/Cas9 was found to impede cotton fiber elongation, while its overexpression promoted fiber elongation, suggesting a positive regulatory function for  GhEXL3  in fiber elongation. Furthermore,  in vitro  ovule culture experiments revealed that the overexpression of  GhEXL3  partially counteracted the inhibitory effects of brassinazole (BRZ) on cotton fiber elongation, providing additional evidence of  GhEXL3  involvement in BR signaling pathways. Moreover, our findings demonstrate that GhBES1.4 directly binds to the E-box (CACGTG) motif in the  GhEXL3  promoter region and enhances its transcription. RNA-seq analysis revealed that overexpression of  GhEXL3  upregulated the expression of  EXPs ,  XTHs , and other genes associated with fiber cell elongation. Overall, our study contributes to understanding the mechanism by which BR regulates the elongation of cotton fibers through the direct modulation of  GhEXL3  expression by GhBES1.4.

This study was supported by the National Natural Science Foundation of China (Grants 32360509, 32301888, and 32350410409), Tianshan Talent Training Program (Grant 2022TSYCCX0087), Key Research and Development Program of Xinjiang (Grant 2022B02052), and the Natural Science Foundation of Henan Province (Grant 232300421253).

http://doi.org/10.1111/tpj.17083