| Cotton is China's main cash crop,Due to the large scale outbreak of Verticillium wilt caused by continuous cropping for many years,the growth and development of cotton has been seriously affected,resulting in a decrease in fiber yield and quality.How to improve the resistance of cotton verticillium is an urgent problem to be solved in the process of cotton breeding.Studies have found that polyamines in plants are closely related to stress resistance,while S-adenosylmethionine decarboxylase(SAMDC)is a key enzyme in the synthesis of polyamines.SAMDC is not only related to the growth and development of plants,but also plays an important role in plant resistance to biotic and abiotic stresses.The latest research found that the island cotton SAMDC gene was transformed into Arabidopsis thaliana,and the resistance of transgenic Arabidopsis to Verticillium wilt was improved,but the mechanism of the disease resistance in cotton is still unclear and needs further study.In this study,the SAMDC family genes in upland cotton were identified,and the function of one of the genes induced by Verticillium dahliae(GhSAMDC7)was analyzed.The results are as follows:1.A total of 14 GhSAMDC genes were obtained from the heterogenous tetraploid Gossypium hirsutum genome database using the reported SAMDC sequence as the probe sequence.The alignment of amino acid multiple sequences of the GhSAMDC genes revealed that the members had a sequence similarity of about 50%.All the family members have the conserved domains unique to the GhSAMDC family: zymosomal cleavage site domain(LSESSLF)and PEST(TIHVTPEDGFSYAS)domain.Chromosome localization analysis revealed that 14 genes were evenly distributed in the A and D genomes.There were 7 GhSAMDC members on each of A and D genome.There was no gene clusters.The results of transcriptome sequencing showed that GhSAMDC1,GhSAMDC7 and GhSAMDC8 had obvious responses to the stress of Verticillium dahliae,suggesting that they play a certain role in the resistance to Verticillium dahliae.2.The pTRV2-GhSAMDC7 vector was constructed and injected into cotton cotyledons mediated by Agrobacterium tumefaciens GV3101,and qPCR was used to verify its silencing effect.After comparing the silenced plants and the control plants infected with Verticillium dahliae,it was found that the plants after gene silencing had reduced disease resistance to Verticillium dahliae and the disease index increased.The stalks browning of the silenced plants was significantly higher than that of control plants.The results indicated that the GhSAMDC7 gene may play a certain role in the process of cotton resistance to Verticillium wilt.3.Plant overexpression vector pCAMBIA2300-GhSAMDC7 of GhSAMDC7 gene was constructed,transformed into Agrobacterium tumefaciens GV3101,and Arabidopsis thaliana was inoculated by silk flower method.Arabidopsis-positive plants were screened by kanamycin and further identified by PCR,and 6 positive plants were obtained.This study laid a foundation for further study of the function of GhSAMDC family genes and analysis of the molecular mechanism of cotton against Verticillium wilt. |
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