| Sclerotinia sclerotiorum is a nectotrophic phytopathogenic fungus that can cause plant diseases such as oil crops,economic crops,and vegetables.Sclerotia as a dormant structure formed on plant surface or inner stem in the late stage of sclerotia disease,which is of great significance in disease cycles and fungal life cycles.During the development of sclerotia,droplet exudate is formed on surface of sclerotia,and its formation mechanism and function are unknown.In addition,carbon sources as a nutrient source have not been systematically reported about the growth and development in S.sclerotiorum.Therefore,the biological characteristics,protein composition and induced necrosis of sclerotial exudate are of great significance for the biology and sclerotial development in S.sclerotiorum,which may be provide a theoretical basis for disease prevention and control of S.sclerotiorum.The results of this research are as follows:(1)The biological characterization of sclerotial exudate was studied.The results showed that pH of sclerotium exudate was higher than that of mycelial secretion,and the total protein in sclerotium exudate was also more than mycelial secretion.Both of them showed the maximum absorption peaks at wavelengths from 340-350 nm.The sclerotial droplet contains rich amino acids,but amino acid concentrations is significantly different.(2)Proteomic analysis of sclerotial exudate,total of 644 proteins were detected(unique peptide > 0),which 258 proteins could be repeatedly expressed.And their protein functions included biological processes involved in substance metabolism and primary metabolic proteins about 42.9%,in terms of molecular function,38.4% of the proteins related to hydrolase activity were present,and the cellular components accounted for 44.6% include the intracellular,intracellular part,cell periphery and intracellular organelles.(3)The results showed that the proteins associated with cell wall degradation(Amy,Cel,and Glu)were highly expressed in sclerotia and Man was increasely expressed in sclerotia at mature stage.The carbon metabolism related protein Gal is elevated expression in the initial and mature stages of sclerotia.The expression level of Pho is higher in hyphae at same time.In addition,pathogenic proteins Abf and Abf precursors are regulared in the hyphae during development.Qualitative and quantitative analysis of the enzyme activity of related proteins revealed that the activity of cellulase and mannanase in sclerotial exudate was significantly higher than that of hyphae,and amylase is no significant difference among exudate and scretion,while acid phosphatase and galactosidase is least in both.Furthermore,sclerotia exudate and mycelia were inoculated on oilseed rape leaves.The results showed that the sclerotial exudate could induced necrosis of leaves tissue,causing lesions similar to mycelial infection.In the early stage after inoculation,the ability of exudate to induce necrosis was stronger than hyphae,but the ability of necrosis induced by the exudate was significantly weakened as mycelial growth.(4)The effects of different carbon sources on mycelial growth and sclerotium development in S.sclerotiorum showed that mycelial growth was inhibited,as increased carbon source concentration,and the inhibitory effect of glucose and galactose was significantly better than lactose.The effect of carbon sources on the accumulation of sclerotia and its biomass was generally inhibited,but 150g/L glucose and 200g/L galactose could promote sclerotial formation.In addition,the proportion of glucose and lactose did not affect the mycelial growth,but a high proportion of lactose inhibits the formation of sclerotia;while glucose and galactose in the ratio of 4:6 produces more sclerotia,but a high proportion of galactosidase inhibits mycelial growth and sclerotia formation.S.sclerotiorum caused a variety of plant diseases and serious economic losses.The formation of sclerotia have an important role in the disease cycles and life cycles.The study about biology and protein composition of sclerotinia exudates and the effects of carbon sources may provide a theoretical basis for the life cycle and sclerotia biology in S.sclerotiorum,and also provide reference for the prevention and control of sclerotinia disease. |
