Disease Resistance Mechanism Of The Disease-resistance Mutant Jusang 1 Of Husang 32

Mulberry diseases are important factors restricting the development of sericulture and the ecological value of mulberry.The studies on the disease resistance mechanisms and the cultivation of new resistant varieties of mulberry tree are beneficial to the realization of the economic and ecological functions of mulberry.Jusang 1 is the natural bud mutation of Husang 32,and it has obvious resistance to a variety of mulberry diseases,but the disease resistance mechanism of its is still unclear.In this study,the Husang 32 and Jusang 1 were used as materials,and the phenotypes and disease resistances of Jusang 1 were identified.Moreover,the chromosome karyotype was detected and the genetic diversity was analyzed using the selceted SSR markers.At the same time,the differentially expressed genes between Husang 32 and Jusang 1 were identified with high-throughput transcriptomic approach,and the genes related to disease resistance were screened.The biological functions of these differentially expressed genes were disccused,and one pathogenesis-related protein gene(Mul-TLP)was selected and its biological functions were studied using transgenic techniques.The information provided may reveal the disease resistance mechanism of Jusang 1 preliminarily and provide a basis to further study of the complicated gene expression regulatory mechanisms in mulberry responses to biotic stress and to explore the genes which have a great potential application value in mulberry biotechnology in future.The main findings are as follows:1.Disease resistance analysis of Jusang 1Husang 32 and its mutant Jusang 1were inoculated with Pst DC3000,Botrytis cinerea,Septogloeum mori,Colletotrichum morifolium and Pseudomonas syri-ngae pv.mori,respectively.The results showed that Jusang 1 had more resistances to all of these pathogens compared with Husang 32.2.Phenotypic difference analysis of Jusang 1 and Husang 32Compared with Husang 32,the branches of Jusang 1 were straight and the lenticels were slightly larger and less.Besides,the surfaces of the leaves were slightly rough.Scanning electron microscopy observsion results showed that the upper epidermal cells of the leaves of Juang 1 were closely packed and undulated,and there were a large number of granules or scale-like waxy ornamentation and ring-shaped raised ridges around the outer arch of the stomata,and the intercellular boundaries between adaxial plane stomata are prominent.3.Genetic diversity analysis between Jusang 1 and Husang 32 based on karyotype and SSR markersUsing the chromosome karyotype analysis technique,the chromosome numbers of Husang 32 and Juang 1 were identified,and the results showed that both of them have 28 chromosomes.Eight SSR primers were selected for the genetic diversity analysis between Jusang 1 and Husang 32,and the results showed that there some of SSR marked sites were different between Jusang 1 and Husang 32.4.Transcriptome difference analysis of Jusang 1 and Husang 32The transcriptome sequencing library of Jusang 1 and Husang 32 were constructed and analyzed,respectively.There were 269,026 unigenes identified,of which 9674 unigenes were expressed differently.Meanwhile,a total of 3103 resistant genes were identified,of which 195 were found to be expressed differently between Jusang 1 and Husang 32.In addation,a total of 2,517 transcription factors were predicted and 133 transcription factors were found to be expressed differently between Jusang 1 and Husang 32.The differential expression of unigenes were involved in the responses to biotic stress,growth and development,metabolic regulation,signal transduction and other physiological processes.5.Study on the biological functions of the pathogenesis-related protein gene(Mul-TLP)One of the differently expressed genes was selected and desigend as Mul-TLP belonging to pathogenesis-related protein gene family.The cDNA of Mul-TLP was cloned using PCR,and its plant expression vector was constructed.Then the transgenic Arabidopsis plants of Mul-TLP were obtained.When the transgenic plants and wild type plants were inoculated with Pst DC3000 and Botrytis cinerea,respectively,the transgenic plants showed more resistances to Pst DC3000 and B.cinerea infections.This indicated that Mul-TLP gene may had a role in enhancing the resistance of Jusang 1.