Characterization And Functional Analysis Of Pyrabactin Resistance-Like Abscisic Acid Receptor Family In Rice

Abscisic acid(ABA)plays crucial roles in regulating plant growth and development,including seed dormancy,germination,and seedling growth.More importantly,ABA is stress-induced hormone,and involved in response to various biological and abiotic stresses,such as drought,salt,low temperature chilling and so on.Rice,as an important food crop,is subject to drought,low temperature and other adversary environment,which seriously threaten rice production and food security.ABA receptors functioned critical roles in ABA-dependent stress-responsive signaling pathway,and always be the hotspots of the abiotic stress research field.Since the discovery of PYR/PYL/RCARs family member of ABA receptor,ABA signal transduction pathway and resistance mechanism had been elucidated and unanimously recognized.However,it is little reported in monocotyledonous rice.The sequence homology analysis showed that there were 13 Os PYLs homologous genes in rice,and three of them(Os PYL11~13)contain a large frangment deletion in the N-terminal or C-terminal,and were considered to be nonfunctional.Therefore,we cloned the rest 10 Os PYLs genes(Os PYL1~10),and studied their expression pattern and biological function.The main results are as follows:1.The expression of the Os PYLs was tissue-specific.Os PYL7/8 were highly expressed in embryo,Os PYL3 and Os PYL5 were highly expressed in leave,Os PYL1 was highly expressed in root,and Os PYL2/9 were highly expressed in all tissues.2.The response of the Os PYLs to ABA is diverse and complex.Some genes were down-regulated by ABA,such as Os PYL1,Os PYL2/9 and Os PYL3; some genes were upregulated by ABA,such as Os PYL4;in addition,some genes were not regulated by ABA,such as Os PYL5,Os PYL7/8,and Os PYL10.3.Os PYLs were localized in both cytosol and nucleus.4.The interaction between the 10 Os PYLs and the 5 Os PP2 Cs were studied in yeast and tobacco,it was found that the interaction between Os PYLs and Os PP2 Cs were diverse and selectively.Some interactions were ABA-dependent,and some were ABA-independent.5.Os PP2 Cs determines the subcellular localization of the Os PYLs-Os PP2 Cs complex in an ABA-independent manner.6.In order to study the biological function of Os PYLs gene,we obtained Os PYL3 and Os PYL9 overexpressing transgenic rice respectively.Germination experiments showed that Os PYL3 and Os PYL9 overexpressing transgenic rice were hypersensitive to ABA at germination stage,and Os PYL9 overexpressing transgenic rice were more sensitive to ABA than Os PYL3 overexpressing transgenic rice.Drought stress experiments showed that Os PYL3 and Os PYL9 overexpressing transgenic rice had higher stomatal closure rate,lower water loss rate,and improved resistance to drought resistance.Cold tolerance experiments showed that the cell membrane stability of Os PYL3 and Os PYL9 overexpressed transgenic rice were increased,and improve the resistance of rice to cold stress.In summary,we comprehensively uncovered the properties of Os PYLs,which may be good candidates for the improvement of abiotic stress tolerance in rice.