| The Mlo gene(Mildew resistance locus o),originally discovered in barley,differs from the R gene in that the mutated recessive allele Mlo confers broad-spectrum resistance to almost all powdery mildew isolates.In addition,Mlo gene also participates in many plant life activities,and affects plant growth and development through differential expression in different tissues.Beet leaf spot disease caused by Mycosphaerella Cercospora beticola Sacc.is a fungal disease that seriously threatens Sugar beet yield.At present,the research on resistance to leaf spot disease is not enough,and its control method is still mainly chemical control,there are serious ecological problems.The research on the relationship between Mlo gene and plant resistance has been applied to a large number of crops,and it is speculated that it may also be a resistance-related gene of Sugar beet.Since there is no report on the relationship between Mlo gene and Sugar beet,the study of Mlo gene in Sugar beet may provide a new theoretical reference and resistance molecular breeding direction for cultivating high-quality varieties.The main findings are as follows:1.In this study,10 member sequences of the Bv Mlo gene family of Sugar beet were finally obtained through the identification of protein sequences,protein structures and conserved domains.The coding region of the Sugar beet Bv Mlo gene family is between 1257 bp?1719 bp,and is scattered on chromosomes 1,3,4,5 and 6,forming two natural gene clusters.It encodes 418?572 amino acids,mostly basic amino acids.Bv Mlo proteins are mostly unstable proteins and mainly amphiphilic proteins,which are mainly hydrophobic.Its amino acid sequence is highly consistent and highly conserved,containing 7?10 conserved motifs and 4?7 transmembrane domains.The ?-helix structure accounts for the largest proportion in the protein secondary structure and contains a large number of phosphorylation sites.Multiple hormone response and abiotic stress elements were found in the promoter region of the Bv Mlo gene family,but only Bv Mlo10 contains a signal peptide.The phylogenetic results showed that most of the Bv Mlo gene family clustered in group VI,which was in the same group as the reported powdery mildew-related genes and tissue expression-related genes.It was speculated that it may also be involved in the interaction between plants and fungal diseases and abiotic stresses.2.In this study,the complete CDS sequence of Bv Mlo2 of 1374 bp and the Bv Mlo7 gene of 870 bp were cloned.The sequence alignment results are correct and have a complete open reading frame.3.The expression levels of Bv Mlo2 and Bv Mlo7 genes were significantly upregulated after induction by Cercospora,among which Bv Mlo2 changed earlier and the expression level was higher.The up-regulated expression of the gene is the key to the successful infection of Cercospora on Sugar beet.It is speculated that both Bv Mlo2 and Bv Mlo7 may play a negative regulatory role in brown spot resistance and are related genes of brown spot susceptibility.The sensitivity of the response is closely related.4.Bv Mlo2 gene was down-regulated under the treatment of SA and Me JA,and its expression was inhibited and almost not expressed in Sugar beet,while Bv Mlo7 was the opposite.Under the treatment of Na Cl and mannitol,Bv Mlo2 gene expression was significantly up-regulated,and Bv Mlo7 was up-regulated more slowly.This indicates that Bv Mlo2 and Bv Mlo7 genes may be involved in various stress responses to varying degrees.It is speculated that the expression and regulation of Bv Mlo2 and Bv Mlo7 genes may enable plants to resist the effects of external stresses,but their functions still need to be further verified. |
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