The Role Of Actin Binding Protein AtADF11 And AtVLN4 In Root Hair Growth Under Drought Stress In Arabidopsis Thaliana

The growth and development of root hairs increase the surface area of roots and the ability of roots to absorb water and nutrients from the external environment,which also plays an extremely important role in plant adaptation to drought stress.The actin filament cytoskeleton is the main cytoskeleton and plays an essential regulatory role in root hair growth.However,the dynamics of actin filaments and their regulatory mechanisms in drought-induced root hair growth remain unclear.Arabidopsis actin binding protein AtVLN4 positively regulates root hair growth.Our laboratory previously found that the actin filament depolymerization factor AtADF11 negatively regulates root hair growth,and drought inhibits its expression.This experiment revealed the role of AtADF11 and AtVLN4 in regulating root hair growth under drought stress by affecting the morphology of actin filaments.The specific research results are as follows:(1)By observing and counting the root hair length and growth rate of wild type(Col-0)under mannitol treatment,the results showed that mannitol treatment promoted Col-0 root hair growth and increased its growth rate,indicating that drought induced rapid root hair growth.By observing and counting the morphological changes of actin filaments and the dynamic changes of single actin filaments in Col-0 root hairs under mannitol treatment,the results showed that under mannitol treatment,the actin filaments in Col-0 root hairs became longer,the frequency of cutting and depolymerization of single actin filaments became smaller,and the frequency of polymerization and binding became larger.(2)By observing and counting the root hair length and growth rate of Atadf11 homozygous mutants under mannitol treatment,the results showed that under mannitol treatment,compared with Col-0,Atadf11 had longer root hairs and a faster growth rate,indicating that AtADF11 was negatively involved in root hair growth under drought.(3)By observing and counting the morphological changes of Atadf11 root hair actin filaments and the dynamic changes of single actin filaments under mannitol treatment,the results showed that under mannitol treatment,Atadf11 actin filaments became longer compared with Col-0,with smaller cleavage and depolymerization rates,suggesting that AtADF11 regulates actin filament cleavage and depolymerization in drought-induced root hair growth.(4)By observing and counting the root hair length and growth rate of Atvln4 homozygous mutants under mannitol treatment,the results showed that under mannitol treatment,compared with Col-0,Atvln4 had shorter root hair length and slower growth rate,indicating that AtVLN4 was positively involved in root hair growth under drought.(5)By observing and counting the morphological changes of Atvln4 root hair actin filaments and the dynamic changes of a single actin filament under mannitol treatment,the results showed that under mannitol treatment,Atvln4 actin filaments became shorter,the rate of polymerization became smaller and the frequency of bundling became larger compared with Col-0,suggesting that AtVLN4 regulates actin filament aggregation and bundling processes in drought-induced root hair growth.In conclusion,the results of this study confirmed that the actin filaments of Arabidopsis root hair cells became longer,with slower frequency of cleavage and depolymerization and faster frequency of aggregation and bundling of a single actin filament became under drought stress.And then,AtADF11 regulates drought-suppressed actin filament cleavage and depolymerization,and AtVLN4 regulates drought-induced actin filament aggregation and bundling.Therefore,AtADF11 and AtVLN4 play an important role in root hair growth by affecting the dynamics of actin filaments under drought stress.