Actin Depolymerization Factor ADF1 Regulated by MYB30 Plays an Important Role in Plant Thermal Adaptation.

Actin filaments are essential for plant adaptation to high temperatures. However, the molecular mechanisms of actin filaments in plant thermal adaptation remain unclear. Here, we found that the expression of Arabidopsis actin depolymerization factor 1 () was repressed by high temperatures. Compared with wild-type seedlings (WT), the mutation of and the overexpression of led to promoted and inhibited plant growth under high temperature conditions, respectively. Further, high temperatures induced the stability of actin filaments in plants. Compared with WT, mutant seedlings showed more stability of actin filaments under normal and high temperature conditions, while the overexpression seedlings showed the opposite results. Additionally, AtMYB30 directly bound to the promoter of at a known AtMYB30 binding site, AACAAAC, and promoted the transcription of under high temperature treatments. Genetic analysis further indicated that AtMYB30 regulated under high temperature treatments. Chinese cabbage ADF1 (BrADF1) was highly homologous with AtADF1. The expression of was inhibited by high temperatures. overexpression inhibited plant growth and reduced the percentage of actin cable and the average length of actin filaments in , which were similar to those of overexpression seedlings. AtADF1 and BrADF1 also affected the expression of some key heat response genes. In conclusion, our results indicate that ADF1 plays an important role in plant thermal adaptation by blocking the high-temperature-induced stability of actin filaments and is directly regulated by MYB30.