| Soil salinization is an important factor that limits land use and agricultural and forestry crop production,seriously constraining the sustainable development of agriculture and forestry and the stability of ecosystems.Mulberry trees are important material foundation for the sericulture industry and have significant economic values.In recent years,with the development of animal husbandry,the reduction of grassland resources,and the intensification of food crisis,mulberry trees as livestock and poultry feed have shown broad prospects for development and utilization.With the implementation of the Western Development Strategy and the Yellow River Basin ecological protection and high-quality development strategy,the sericulture industry is gradually shifting to inland arid and saline areas.Therefore,exploring salt tolerant genes of mulberry trees and cultivating new varieties of salt tolerant mulberry trees is of great significance for improving the efficiency of salt alkali land resource development and utilization,promoting sustainable development of agriculture and forestry,and enhancing national ecological security.In this study,the salt hypersensitivity(SOS)pathway genes of Husang 32(MulSOSs)were cloned,and the structure and evolutionary relationship of mulberry SOS proteins were analyzed.Furthermore,the tissue expression and induced expression characteristics of MulSOS genes were explored,and the promoter of MulSOS2 gene(p MulSOS2)was cloned and its expression characteristics were analyzed.Meanwhile,the binding ability of MulASIL transcription factors with p MulSOS2 and the regulation of it on the activity of p MulSOS2 were discussed.In addition,the salt tolerance function of MulASIL and MulSOS2 were clarified.The main results of this study were summarized as follows:(1)Cloning and analysis of MulSOS gene in mulberry Six MulSOS genes(Named as MulSOS1-6)were obtained and their coding proteins have different conservative motifs,subcellular localizations,3D structures and protein interaction networks;The amino acid sequence conservation between different MulSOS proteins is poor,but the conserved domain homology of the same SOS protein in different plants is high.(2)Expression patterns of the MulSOS genes Except for the MulSOS5 gene,the expressions of other MulSOS genes are induced by Na Cl stress,but different MulSOS genes have different expression patterns.In addition,different MulSOS genes also have different induced expression patterns of response to ABA,gibberellin(GA)and methyl jasmonic acid(Me JA);The MulSOS genes are expressed in various tissues of mulberry trees,without tissue specificity.Among them,MulSOS1,MulSOS2,MulSOS5,and MulSOS6 genes are highly expressed in leaves,while MulSOS3 and MulSOS4 genes are highly expressed in roots.(3)Cloning and analysis of the promoter of MulSOS gene The promoter of MulSOS gene(p MulSOS2)was cloned and the nucleotide sequence of p MulSOS2 was analyzed It was showed that the p MulSOS2 contains various plant hormone responsive elements such as ABA and Me JA,as well as binding sites for transcription factors such as Trihelix and MYB.It has light,SA,ABA,and Me JA induced expression activities.(4)Salt tolerance analysis of MulSOS2 gene Our results showed that over-expression of MulSOS2 gene in Arabidopsis can increase the accumulation of proline in transgenic plants under salt stress,reduce the synthesis of malondialdehyde,and enhance the salt tolerance of transgenic Arabidopsis plants.Meanwhile,it was showed that instantaneous expression of MulSOS2 gene in mulberry leaves and stable expression of the gene in hairy roots can enhance the salt tolerance ability of the transgenic leaves or the transgenic hairy roots mulberry plants.(5)Regulation of MulASIL on the expression of MulSOS2 gene Our results showed that the MulASIL transcription factor can bind to the promoter of MulSOS2 gene,and enhance the transcriptional activity of the promoter.Furthermore,it was showed that overexpression of the MulASIL gene in the hairy roots of mulberry trees can significantly promote the expression of the MulSOS2 gene and improve the salt tolerance of transgenic mulberry trees. |
