The Molecular Mechanisms Of AtZFP5,AtZFP6,AtGIS3 And OsRHL41-like Genes In Regulation Of Root Hair Growth And Development

Root is an important nutritional organ of plants.Root hairs are specialized root epidermis cells and an important part of plant root.They can increase the contact areas between soil,and more efficiently uptake water and nutrients.Therefore,they have great academic and economic significance to study the mechanism of cell differentiation and patterning in plant development.In this study,the experiments were conducted to study the functions of C2H2 zinc finger proteins,including ZFP5,ZFP6 and GIS3 on root epiedermal cell development in Arabidopsis.More importantly,we also study the functions of OsRHL41-like,OsRHD1-like,OsRHD2-likel and OsRHD2-like2 on root hair development in rice.The main results are as follows:1.In order to study ZFP5 responds to nutrient signaling to regulate root hair development.Our results showed that Pi and potassium deficiency significantly induced the expression of ZFP5,but could not restore the shorter root hair phenotype of zfp5 mutant and ZFP5 RNAi lines to wild type level.Molecular and genetic studies show that ethylene is involved in Pi and potassium deficiency-induced root hair elongation.Moreover,ZFP5 responds to Pi and potassium deficiency-induced root hair elongation through ethylene signaling by mainly regulating transcription of EIN2.2.In order to study the molecular mechanism of GIS3 regulating root hair development,phenotypic experiments demonstrated that that gis3 mutant and GIS3 RNAi transgenic line showed significant reductions in root hairs,which suggests that GIS3 positively regulates root hair development in Arabidopsis.The applications of exogenous ACC and a synthetic cytokinin,BA,significantly induced the expression of GIS3,but it could not restore root hair length in gis3 mutant.More importantly,molecular and genetic studies reveal that GIS3 acts upstream of RHD2 and RHD4 by directly binding to their promoters.Taken together,we can conclude that GIS3 regulates root hair growth and development by directly targeting RHD2 and RHD4 expression through ethylene and cytokinin signals in Arabidopsis.3.In order to expore the function of ZFP6 in regulating root hair development,the phenotypic analysis of the phenotypes of zfp6 mutant and ZFP6 RNAi transgenic line showed that ZFP6 positively regulated root hair development.The applications of ACC and BA significantly induced the expression of ZFP6 in wild-type,while treatments of ACC and BA significantly could not restore root hair length in zfp6 mutant.The results demonstrate that ZFP6 regulates root hair elongation in response to ethylene and cytokinin.Analysis of RNA-Seq screens 13 hormone-related genes,and yeast two-hybrid analysis shows that ZFP6 might interact with AT4G36110,MYB51,ERF6,ATMYBL2.4.In order to investigate the relationship of auxin,ethylene,and cytokinin,we found only ethylene induces ectopic root hair cells in wild-type plants,which indicates a special role of ethylene in the hair initiation stage.In the subsequent elongation stage,auxin,ethylene,and cytokinin could enhance root hair tip growth equally.Our results data showed that the effect of cytokinin is independent from auxin and ethylene in this process.Exogenous cytokinin restores root hair elongation when the auxin and ethylene signal is defective.Notably,transcriptional analyses demonstrate that auxin,ethylene,and cytokinin regulate the expression of RSL4 and then regulate a similar set of root hair-specific genes in regulating root hair development in Arabidopsis.5.In order to investigate the functions of rice genes regulating root hair development,we cloned four genes in rice,and then transferred to Arabidopsis and rice.They are OsRHL41-like?OsRHD1-like?OsRHD2-likel andOsRHD2-like2.Over-expression of OsRHL41-like significantly increased root hair length of Arabidopsis and rice in comparison to wild-type,while the root hair length of OsRHL41-like interfering line showed the oppsite phenotype.These results indicate that OsRHL41-like positively regulates root hair length.OsRHD2-likel and OsRHD2-like2 transgenic lines have the similar phenotype of OsRHL41-like,which suggests that OsRHD2-likel and OsRHD2-like2 positively regulate root hair length.In contrast,there is opposite phenotype of OsRHD1-like transgenic lines,suggests that OsRHD1-like negatively regulates root hair length in rice.