| Drought and salinization are one of the major abiotic hazards in plants today.The main mechanism is to cause the inconsistency of the internal and external osmotic pressure of plants to dehydrate the body.Myrothamnus flabellifolia is the only woody resuscitation plant in the world,which exhibits strong drought tolerance.In this study,we cloned a dehydrationinduced MfWRKY17 gene fromMyrothamnus flabellifolia and transferred it into wild-type Arabidopsis,then we investigated its functions under drought and salt stresses.The main results obtained were list below:(1)Sequence analysis and genetic transformation: the MfWRKY17 gene was isolated from the Myrothamnus flabellifolia genome by homologous cloning,and its core coding region was 999 bp,encoding 332 amino acids,belonging to the second type of WRKY transcription factor family.The analysis of evolutionary tree shows that its homology with Elaeis guineensis and Nelumbo nucifera is relatively high,but it is only 34%,indicating that MfWRKY17 gene is more conservative and has fewer homologous species.The overexpression T3 generation of pure line plants was obtained by floral-dip method and resistance screening was conducted with kanamycin.By constructing the 35S:MfWRKY17-p HB-YFP fusion vector,the fluorescence signal was detected in the tobacco leaves,and it was found to be located in the nucleus.(2)Phenotypic results:in seedling treatment,overexpressed and wild-type plants were treated with different concentrations of mannitol(200mM,250 mM)and Na Cl(100mM,150 mM),and we observed that the overexpression plants’(named Line-F and the Line-M)root length were significantly longer than wild type plants;In the adult-plant treatment,the growth and green rate of leaves of overexpression plants was better than that of wild-type plants in natural drought and 300 mM NaCl conditions.(3)Changes in physiological indexes:In the treatment of water loss rate,the water loss rate of over-expressed plant Line-F was always lower than that of wild type plants,and the water loss rate of Line-M was significantly less than that of wild type plants after 3h;in the treatment of proline,the proline content of overexpressed plants in the drought was about 30μg/g,which was significantly higher than that of WT,while the proline content of Line-F and Line-M in the salt stress were about 34μg/g and 40μg/g respectively,and were significantly higher than that of wild type plants;in stomatal treatment,the stomatal opening degree of overexpressed plants in drought was significantly smaller than that of wild-type plants,which showed more drought resistance.in chlorophyll treatment,the chlorophyll content of overexpressed plants in sodium chloride was about 2.2mg/g,significantly higher than that before treatment,and significantly higher than the wild-type plants.(4)The wild-type and overexpression plants were treated with natural drought and 200 mM sodium chloride,and the five genes of NCED3,RD22,P5CS5,RD29A and RAB18 were determined in vivo.Under natural drought conditions,the expression of NCED3,RD22,RD29A and RAB18 genes in the plants of MfWRKY17 was significantly higher than that in the wild-type plants,indicating that MfWRKY17 affected the expression of these four genes,possibly by improving the expression of these four genes to improve the drought resistance.The expression level of P5CS5 gene was significantly lower than that of wild-type plants or no difference most of the time after treatment,and it was speculated that MfWRKY17 promoted the down-regulation expression of P5CS5 gene under drought conditions.Under 200 mM Na Cl treatment,the expression of NCED3,P5CS5 and RAB18 genes in MfWRKY17 plants was significantly higher than that of WT at most time points,and the expression level was significantly up-regulated.It was speculated that the expression of MfWRKY17 gene could affect the expression of these three genes in high salt conditions,possibly by enhancing the expression of these three genes to improve the salt tolerance.However,the expression levels of RD22 and RD29A gene in the overexpression plant Line-F were significantly different from that in the RD29A gene,and the expression level of Line-F was significantly higher than that of WT in most of the time before and after treatment,while the Line-M had almost no difference with WT,and the prediction could be that the difference between the plant lines was caused by the difference in the inserted site of the MfWRKY17 gene in wild-type Arabidopsis thaliana.To sum up,the MfWRKY17-overexpressing plants showed good drought resistance and salt resistance. |
