Identification Of Cucumber Powdery Mildew Resistance Protein(Cucumis Sativus L.)

Powdery mildew caused by Podosphaera xanthii is one of the major diseases in cucumber(Cucumis sativus L.),resulting substantial yield losses.The selection and breeding of cucumber cultivars with high resistance to powdery mildew is one of the effective approach to overcome the hazard of powdery mildew.Several researches indicated that some resistance genes were involved in powdery mildew resistance for different cucumber cultivars,however,the mechanisms of how the resistance protein mediate powdery mildew resistance in cucumber is unkown.In present study,the substituted segment line 'SSL508-28' with high resistance to powdery mildew and the powdery mildew receptor parent 'D8' were applied to investigate the differential expressed proteins caused by the powdery mildew inoculation by iTRAQ(isobaric tags for relative and absolute quantitation).qRT-PCR(quantificational real-time polymerase chain reaction)was used to analyze the gene expression levels of some resistance-associated proteins in the 'SSL508-28' under 48 h inoculation of powdery mildew.The major results are shown as follows:1.Totally,3629 proteins with quantitative information were identified by using iTRAQ technology,of which 151 were differentially expressed(FDR ? 0.05,Fold changes ? 2)in'SSL508-28' and 'D8'.38 common proteins were detected in both 'SSL508-28' and 'D8',which included glutathione S-transferases,oxygenation-enhancing proteins,peroxidase 73.79 proteins were detected in the resistant line 'SSL508-28',which included polygalacturonase-inhibiting protein,ribosome-recycling factor,malate dehydrogenase,remorin protein,DNA damage repair/resistance protein DRT100.34 proteins were detected only in the susceptible line'D8',which inculded including glyceraldehyde-3-phosphate dehydrogenase and 50S ribosomal protein.7 candidate proteins were selected based on bioinformatic analysis and functional annotation analysis.2.qRT-PCR was used to detect the expression level of the corresponding genes of the 7 candidate proteins in the 'SSL508-28' under 48h inoculation of powdery mildew.The results indicated that the expression level of Csa4M290740.1(DNA damage repair/tolerance protein DRT100,belonging to the LRR resistance(R)protein)was significantly up-regulated in'SSL508-28'.3.The gene expression levels of Csa4M290740.1 in cucumber lines with different powdery mildew resistance were analyzed by qRT-PCR.It was indicated that the expression level of Csa4M290740.1 was higher in resistant lines than that in susceptible lines.The highest expression level was found in donor parents 'Jin5-508',and the lowest was in 'D8'.In this study,the proteins associated with powdery mildew resistance in cucumber were isolated,and one candidate protein that might control the resistance was analyzed.The outcome of this study will help us to accelerate the cucumber genetic resources innovation of powdery mildew,and provide new insights of molecular mechanism involved in powdery mildew resistance of cucumber.