Analysis Of Differentially Expressed Genes For Salt Tolerance Between Males And Females Plants Of Salix Linearistipularis Based On RNA-seq

Soil salinization is the main factor affecting plant growth and development.Salt stress mainly causes damage to plants through osmotic stress,ionic stress and high p H stress.Salix linearistipularis is a perennial woody plant naturally distributed in the saline-alkali land of Songnen Plain in Northeast China.Salix linearistipularis is a typical dioecious plant,and male and female plants have great differences in salt tolerance.Therefore,it is important to explore the molecular mechanism of the difference in salt tolerance between male and female plants for improving soil salinization.Based on the previous research on the effect of nitrogen metabolism on the seed germination of Salix linearistipularis,wild Salix linearistipularis seeds and male and female perennial wild Salix linearistipularis plants grown on saline-alkali land were used as experimental materials to preliminarily explore the nitrogen response differences between male and female plants of Salix linearistipularis to salt stress.The molecular mechanism of hormone metabolism was established,which laid a theoretical foundation for the molecular improvement and seedling cultivation of Salix linearistipularis under saline-alkali stress.The specific research results are as follows:1.The inhibitory effect of salt stress on male plants of Salix linearistipularis was significantly higher than that of female plants.The urea content in male and female plants of Salix linearistipularis was significantly increased after salt stress treatment,and the urea content in male plants was significantly higher than that in female plants.The accumulation of urea significantly enhanced the inhibitory effect of salt stress on the growth of Salix linearistipularis,and there was a certain correlation between nitrogen metabolism and the difference in salt tolerance between male and female plants of Salix linearistipularis.2.Analyzing the root transcriptome data of male and female plants of Salix linearistipularis under salt stress,27 up-regulated differentially expressed genes（up-regulated in female plants and down-regulated in male plants after salt treatment）and 39 down-regulated differentially expressed genes（salt treatment）were obtained.After treatment,the expression was down-regulated in female plants and up-regulated in male plants).The results of enrichment analysis showed that the differentially expressed genes were annotated into 28 GO functional classes,which were mainly involved in the"redox","transmembrane transport"and"metabolic pathways"of plants.3.The results of q RT-PCR and semi-quantitative RT-PCR showed that the expression results of six differentially expressed genes in male and female plants were consistent with the transcriptome data.Among them,the expression level of DHDPS,a key gene of lysine synthesis pathway,changed significantly after salt treatment,which was up-regulated by 4.5times in female plants and down-regulated by 2 times in male plants.4.By adding different concentrations of Lysine to the medium treated with salt stress,with the increase of Lysine concentration,the inhibitory effect of salt stress on the seed germination and seedling growth of Salix linearistipularis decreased continuously.The contents of urea and Lysine in Salix linearistipularis seedlings decreased significantly.The expression levels of the key genes AK,DHDPS,LKR,SDH in the lysine synthesis and decomposition pathway and the key genes NHX1,SOS1,P5CS1 and WRKY1 in response to salt stress were significantly increased.At the same time,the addition of exogenous lysine also significantly alleviated the inhibitory effect of salt stress on the growth of male and female plants of Salix linearistipularis.Tolerance of Salix linearistipularis to salt stress.5.DHDPS,the key gene of lysine synthesis pathway,is expressed in the roots,stems and leaves of male and female plants of Salix linearistipularis,responds to Na Cl,NH₄Cl,urea,Lysine,GA₃,and ABA,and is differentially expressed in male and female plants,DHDPS was also differentially expressed in the roots of male and female plants in the presence of salt and nitrogen.In conclusion,urea can significantly enhance the inhibitory effect of salt stress on the growth of Salix linearistipularis,and exogenous lysine may enhance the tolerance of Salix linearistipularis to salt stress by promoting the decomposition and utilization of urea and lysine.