Functional Analysis Of Cotton ABA Receptor GhPYL9-5D,GhPYL6-2A And GhPYR1-3A

Abscisic acid(ABA)is an important hormone in plants.It regulates seed maturation and dormancy,seedling growth,leaf senescence and stomatal movement,and so on.ABA also participates in the regulation of various abiotic stresses,such as drought,high salt and cold.When it works,ABA must bind to ABA receptor pyrabactin resistance1/PYR1-like/regulatory components of ABA receptor pyrabactin resistance1/PYR1-like/regulatory components of ABA receptor(PYR1/PYL/RCAR).At present,much advance has been achieved in studying the function of PYLs in Arabidopsis thaliana.However,knowledge about PYLs in cotton is largely unknown.In this study,three homologus genes of Arabidopsis AtPYL9,AtPYL6 and AtPYLRl from cotton TM-1 were cloned,and were named GhPYL9-5D,GhPYL6-2A and GhPYR1-3A respectively.The functions of these three genes were analyzed and the results are as follows:GhPYL9-5D was expressed in cotton root,stem,leaf,flower and fiber.It was highly expressed in flowers.The expression level of GhPYL9-5D increased under drought stress but decreased under ABA treatment.GhPYL9-5D can interact with GhPP2CAs in the absence or presence of ABA.The GUS staining result showed that GhPYL9-5D was expressed in roots,stems,leaves,flowers and siliques of Arabidopsis thaliana,and its encoded protein was localized in plasmal membrane.Overexpression of GhPYL9-5D in Arabidopsis clearly enhanced the sensitivity of seed germination to ABA.Moreover,the expression levels of AtABI3 and AtABI5 were significantly higher in transgenic lines than in WT plants during seed germination in the presence of ABA.The GhPYLP-5D-overexpression Arabidopsis lines exhibited reduced sensitivity of seed germination to mannitol or NaCl stress Furthermore,the relative expression of AtABAl was significantly decreased in the transgenic plant seeds compared with WT during germination under mannitol stress.Additionally,the growth of primary root of GhPYL9-5D transgenics plants was more sensitive to ABA but insensitive to mannitol treatment.Under ABA treatment,the length of meristem and cell number in the meristem were reduced in the GhPYL9-5D overexpression lines Overexpression of GhPYL9-5D accelerated ABA-induced leaf senescence of Arabidopsis thaliana.Overexpression of GhPYL9-5D enhanced plants drought resistance in Arabidopsis.GhPYL6-2A was expressed in cotton roots,stems and flowers,and dominantly expressed in roots.The expression level of GhPYL6-2A was up regulated under drought stress but down regulated under ABA treatment.GhPYL6-2A can interact with GhPP2CAs,Overexpression of GhPYL6-2A enhanced plant sensitivity to ABA treatment,mannitol and NaC1 stress during seed germination and early seedling growth.GhPYR1-3A was expressed in cotton roots,stems,leaves,flowers and fibers,and preferentially expressed in stems.GhPYRl-SA was down regulated under ABA treatment or drought stress.GhPYR1-3A can interact with GhPP2CAs.Overexpression of GhPYRl-3A enhanced the sensitivity of seed germination to ABA treatment,mannitol and NaCl stress.In addition,the transgenic plants displayed enhanced the sensitivity of seedling growth to ABA treatment and mannitol stress.From the above results,the following conclusions are drawn:GhPYL9-5D,GhPYL6-2A and GhPYRl-3A have basic characteristics of ABA receptors.They played crucial roles in response to ABA,salt and osmotic stress.Overexpression of GhPYL9-5D enhanced Arabidopsis drought resistance.