Arabidopsis MYB21 Negatively Regulates KTN1 to Fine-Tune the Filament Elongation

The growth process of the stamen filament is crucial for plant reproduction. However, the molecular mechanisms underlying the regulation of filament growth remain largely unclear. Our study has identified that MYB21 is involved in the regulation of filament growth in Arabidopsis. In comparison to the wild type, the cell length of the filaments is notably reduced in the myb21 mutant. Moreover, we found that KTN1, which encodes a microtubule-severing enzyme, is significantly upregulated in the myb21 mutant. Additionally, yeast one-hybrid assays demonstrated that MYB21 can bind to the promoter region of KTN1, suggesting that MYB21 might directly regulate the expression of KTN1. Finally, transcriptional activity experiments showed that MYB21 is capable of suppressing the driving activity of the KTN1 promoter. This study indicates that the MYB21-KTN1 module may play a precise regulatory role in the growth of Arabidopsis filament cells.