Abstract
BackgroundCucumber (Cucumis sativus L.) is a widely planted vegetable crop that suffers from various pathogen infections. Powdery mildew (PM) is typical disease caused by Sphaerotheca fuliginea infection and destroys the production of cucumber. However, the metabolic responses to S. fuliginea infection are largely unknown.ResultsIn our study, a PM resistant variety ‘BK2’ and a susceptible variety ‘H136’ were used to screen differentially accumulated metabolites (DAMs) and differentially expressed genes (DEGs) under S. fuliginea infection. Most of DEGs and DAMs were enriched in several primary and secondary metabolic pathways, including flavonoid, hormone, fatty acid and diterpenoid metabolisms. Our data showed that many flavonoid-related metabolites were significantly accumulated in BK2 rather than H136, suggesting an essential role of flavonoids in formation of resistant quality. Changes in expression of CYP73A, CYP81E1, CHS, F3H, HCT and F3’M genes provided a probable explanation for the differential accumulation of flavonoid-related metabolites. Interestingly, more hormone-related DEGs were detected in BK2 compared to H136, suggesting a violent response of hormone signaling pathways in the PM-resistant variety. The number of fatty acid metabolism-related DAMs in H136 was larger than that in BK2, indicating an active fatty acid metabolism in the PM-susceptible variety.ConclusionsMany differentially expressed transcription factor genes were identified under S. fuliginea infection, providing some potential regulators for the improvement of PM resistance. PM resistance of cucumber was controlled by a complex network consisting of various hormonal and metabolic pathways.
Highlights
Cucumber (Cucumis sativus L.) is a widely planted vegetable crop that suffers from various pathogen infections
Cluster I included the genes that were induced by S. fuliginea infection in both BK2 and H136; Clusters VII and X included the genes that were reduced by S. fuliginea infection in both BK2 and H136; Cluster VI included the genes that were down-regulated in BK2 and up-regulated in H136; and Cluster III included the genes that were up-regulated in BK2 and down-regulated in H136 (Fig. 1b)
According to the criation of |log2foldchange| > 1 and P < 0.05, a large number of Differentially expressed gene (DEG) were identified in different comparisons, including 416 up- and 449 down-regulated genes in the H136T vs H136 treated with control solution (H136C) comparison, 1706 up- and 1973 down-regulated genes in the BK2T vs H136C comparsion, 2394 up- and 3438 down-regulated in the H136T vs BK2T comparison, and 1174 up- and 1855 downregulated in the H136C vs BK2 treated with control solution (BK2C) comparison (Fig. 1c)
Summary
Cucumber (Cucumis sativus L.) is a widely planted vegetable crop that suffers from various pathogen infections. Powdery mildew (PM) is typical disease caused by Sphaerotheca fuliginea infection and destroys the production of cucumber. The metabolic responses to S. fuliginea infection are largely unknown. Cucumber (Cucumis sativus L.) is an economically significant vegetable crop widely planted in many countries (http://faostats.fao.org). Its production is largely limited by various infective agents, including bacterial, viral, fungal and oomycete [1, 2]. Powdery mildew (PW) is typical disease that was caused by Sphaerotheca fuliginea infection and destroys the production of cucumber in many regions [3]. After breaking through the cell wall barrier, S. fuliginea develops a haustorium and absorbs nutrients from the host plants [6, 7]
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