Gene Cloning, Purification And Inducing Multiple Defense Responses In Plants Of A Novel Protein Elicitor-SsCut From Sclerotinia Sclerotiorum

Stem rot caused by Sclerotinia sclerotiorum is an important disease on oilseed rape. At present, we can grow resistant varieties, strengthen the management of cultivation, and use chemical fungicide treatment for the prevention and control of the disease. But now, biological control can contribute to the sustainable development of agriculture, and has attracted more and more attention in recent years. Elicitors can rigger the plant immune system by receptor molecules on the surface of cells, not by sterilization. Theses receptor molecules can trigger signal transduction, as well as expression of defense genes. The elicitors have many advantages over chemical pesticide and can be used as a new type of microbe protein pesticide to solve agricultural pest and disease problems.In this study, we report the cloning of the SsCut gene （GenBank Accession No. XM₀01590986.1） encoding cutinase from Sclerotinia sclerotiorum. We isolated a 609-bp cDNA encoding a polypeptide of 202 amino acids with a molecular weight of 20.4 kDa. Heterologous expression of SsCut in Escherichia coli （His-SsCut） caused the formation of lesions in tobacco that closely resembled hypersensitive response lesions. His-SsCut was caused cell death in Arabidopsis, soybean （Glycine max）, oilseed rape （Brassica napus）, rice （Oryza sativa）, maize （Zea mays）, and wheat （Triticum aestivum）, indicating that both dicot and monocot species are responsive to the elicitor. Furthermore, compounds related to disease resistance including hydrogen peroxide, phenylalanine ammonia-lyase, peroxides, and polyphenol oxidase increased markedly after His-SsCut treatment. His-SsCut-treated plants exhibited enhanced resistance as indicated by a significant reduction in the number and size of S. sclerotiorum, Phytophthora sojae, and P. nicotianae lesions on leaves relative to controls. Real-time PCR results indicated that the expression of defense-related genes and genes involved in signal transduction were induced by His-SsCut.Our results demonstrate that His-SsCut is an elicitor that triggers defense responses in plants and will help to clarify its relationship to downstream signaling pathways that induce defense responses.