Molecular Mechanism Study Of ThNAC12 In Response To Salt Stress In Tamarix Hispida

During the growth and development of plants,they often suffer from various abiotic stresses affected by the external environment,such as salt stress,drought stress,cold stress or other abiotic stress.A variety of physiological changes and molecular regulation mechanisms in plants will be evolved to varying degrees in response to the stress,when plants are subjected to abiotic stress.An overwhelming majority of different genes play an important role in this defense mechanism to against abiotic stress.The NAC family of transcription factors are important regulatory factors in plants,which involved in the regulation of a variety of growth and development processes,for instance,differentiations,influence on flowering,and response to abiotic stress.Previous investigations have revealed that NAC transcription factors are involved in plant response to adversity stress.In this study,we will explore the gene function and stress resistance mechanism of ThNAC12 gene in Tamarix hispida.In previous studies,it was determined that the aquaporin ThPIP2;5 in T.hispida can enhance the salt tolerance of transgenic plants under salt stress.The cis-acting element NACRS associated with stress was found in the promoter of ThPIP2;5 gene,it screened out the ThNAC12 gene in the cDNA library of T.hispida,which is a member of the NAC transcription factor in T.hispida.We speculate that ThNAC12 may be the upstream regulatory factor of ThPIP2;5 protein.In order to verity weather the ThNAC12 transcripation factor can regulate ThPIP2;5 protein,YIH,ChIP-PCR and Dual luciferase reporter assay were used,respectively.The investigation shown that the ThNAC12 gene can specially bind to the promoter of ThPIP2;5,and directly regulate the functional expression of ThPIP2;5 protein.The result was confirmed that ThPIP2;5 is the downstream target protein of ThNAC12.It is demonstrated that the ThNAC12 is a typical NACs,is a nuclear localization protein,and has transcriptional activator activity by analyzing the biological function of the ThNAC12 transcription factor.Since ThPIP2;5 protein exhibited the strong stress resistance under salt stress,and the ThNAC12 as its upstream regulate factor,we suspected the ThNAC12 also has the salt tolerance.In order to prove the guess,the expression pattern of ThNAC12 gene in the T.hispida and 84K poplar(P.alba× P.glandulose)was further analyzed.Transient transformation of T.hispida histochemical staining and measuring physiological indexes under salt stress,the results show that ThNAC12 gene overexpression of T.hispida MDA,H2O2 and O2·-content significantly decreased,CAT,SOD and POD activity increased significantly.However,the means that ThNAC12 gene can obviously improve the salt resistance of T.hispida by mediate Reactive oxygen species scavenging capability,reduce the damage of cell membrane,enhance the antioxidant capacity,and significantly increase the salt tolerance of transgenic T.hispida.The overexpression poplar were obtained,histochemical staining and measuring physiological indexes under salt stress,the results showed the same trend as the result of T.hispida stress.The phenotypes were further observed and the grown parameters were measured,the conclusion reveal that fresh weight/dry weight ratio and chlorophyll content of transgenic poplar increased dramatically,and the plant height is slightly higher than that of 84K poplar;it is demonstrated that the ThNAC12 gene can reduce water loss and increase net photosynthetic rate of transgenic poplars under salt stress.The above results determined an important molecular regulation mechanism of ThNAC12-ThPIP2;5 mediated stress resistance in T.hispida.The ThNAC12 gene activates the function of ThPIP2;5 protein by binding to the NACRs element on the promoter of the ThPIP2;5 gene,and enhance the salt tolerance of transgenic plants.