Sun Yaru, Jin Shuangxia, Song Guoli
National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, Hubei, China.
State Key Laboratory of Cotton Bio-Breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, 455000, China.
Plant Cell Rep. 2025 Jan 10;44(2):26. doi: 10.1007/s00299-024-03422-5.
Cotton GhMAX2 positively regulates fiber elongation by mediating the degradation of GhS1FA, which transcriptionally represses GhKCS9 expression. Strigolactones (SLs) are known to promote cotton fiber development. However, the precise molecular relationship between SL signaling and fiber cell elongation remains unclear. In this study, we investigate the role of F-box E3 ligase MORE AXILLARY GROWTH2 (MAX2) in upland cotton in relation to the regulation of fiber development. GhMAX2b and GhMAX2f act as key components for SL signal transduction, with their loss-of-function leading to a notable reduction in fiber length. Biochemical analysis showed that GhMAX2b/f trigger the ubiquitination and subsequent degradation of the transcription repressor strigolactone-1-factor-At (GhS1FA), which function as a substrate for these E3 ligases. Furthermore, GhS1FA inhibits fatty acids biosynthesis by directly binding to the W-box element within the promoter of 3-ketoacyl-CoA synthases 9 (GhKCS9) and repressing its expression. In summary, we propose that GhMAX2b/f promote fiber elongation, potentially operating partially independently of GhD53 degradation.
棉花GhMAX2通过介导GhS1FA的降解来正向调控纤维伸长，而GhS1FA可转录抑制GhKCS9的表达。已知独脚金内酯（SLs）可促进棉花纤维发育。然而，SL信号传导与纤维细胞伸长之间精确的分子关系仍不清楚。在本研究中，我们研究了F-box E3连接酶多腋芽生长2（MAX2）在陆地棉纤维发育调控中的作用。GhMAX2b和GhMAX2f作为SL信号转导的关键组分，其功能丧失导致纤维长度显著降低。生化分析表明，GhMAX2b/f触发转录抑制因子独脚金内酯-1-因子-At（GhS1FA）的泛素化及随后的降解，GhS1FA作为这些E3连接酶的底物发挥作用。此外，GhSFA1通过直接结合3-酮脂酰-CoA合酶9（GhKCS9）启动子内的W-box元件并抑制其表达，从而抑制脂肪酸生物合成。总之，我们提出GhMAX2b/f促进纤维伸长，可能部分独立于GhD53的降解发挥作用。
