The Role Of Actin Depolymerization Protein AtADF8 In Root Hair Growth In Arabidopsis Thaliana

Root hairs can increase the surface area of plant roots and play a vital role in the process of absorbing external water and nutrients.The actin skeleton is a main component of the cytoskeleton and is a key factor in the regulation of root hairs growth.However,the molecular mechanism of root hair growth regulation by the actin skeleton remains unclear.AtADF8 is an actin depolymeriaing protein of Arabidopsis thaliana,which was specifically expressed in root hairs.In this experiment,we observed the role of AtADF8 in regulating root hair growth.We obtained the following results:1.Homozygous mutants of Atadf8 were identified by the triple priming method.AtADF8::GFP/Atadf8 homozygous plants were obtained by vector construction and the complement mutant plants of AtADF8::GFP/Atadf8(AtADF8 comp)were verified by q RT-PCR.2.The growth process of root hairs was observed by stereoscopic microscope.Compared with Col-0,the root hair length,the growth rate and growth time of Atadf8 mutant decreased significantly,while AtADF8 comp was similar to Col-0.It was indicated that AtADF8 positively regulates root hairs growth.3.Observ the actin filament morphology in root hairs using laser confocal microscopy.During the fast-growing period the actin filament dynamic of the Atadf8 in the apical region of root hairs were similar to that of Col-0,but the actin filament in the subapical region were more stable.Compared with Col-0,the actin filament dynamic of the Atadf8 were more stable in both apica and subapical regions during the slow-growing and fully-grown period,but the difference between the two was more obvious during the slow-growing period.The above shows that AtADF8 promotes the depolymerization of actin filaments during root hair growth.4.By qRT-PCR and Western-blot assay,it was found that the transcription and protein expression levels of AtADF8 were significantly increased after ethephon treatment,while its expression was significantly decreased after 1-MCP treatment.In addition,after ethephon treatment,the root hair length of Col-0 was significantly increased and the growth rate was accelerated and the growth time was prolonged.The results were opposite after 1-MCP treatment.The root hair growth of Atadf8 was not change signifisently under 2 kinds of ethylene special drug treatments.The depolyerization of actin filament in apical and subapical region of Col-0 root hairs were increased under ethephon treatment.Under 1-MCP treatment,the stabiloty of actin filaments increased.The action filament dynamic in root hairs of Atadf8 were not sensitive to ethylene special drug.These results indicate that ethylene signaling regulates the rule of AtADF8 in the regulation of root hair growth.In conclusion,this experiment demonstrated that AtADF8 is activated by ethylene signaling during root hairs growth and promotes the depolymerization of actin filaments resulting in the promotion of root hair growth.