Abstract
Fusarium wilt (FW) of cucumber (Cucumis sativus L.) caused by Fusarium oxysporum f. sp. cucumerinum (Foc) is a destructive soil-borne disease that severely decreases cucumber yield and quality worldwide. MicroRNAs (miRNAs) are small non-coding RNAs (sRNAs) that are important for regulating host immunity because they affect target gene expression. However, the specific miRNAs and the miRNA/target gene crosstalk involved in cucumber resistance to FW remain unknown. In this study, we compared sRNA-seq and RNA-seq data for cucumber cultivar ‘Rijiecheng’, which is resistant to FW. The integrated analysis identified FW-responsive miRNAs and their target genes. On the basis of verified expression levels, we detected two highly expressed miRNAs with down-regulated expression in response to Foc. Moreover, an analysis of 21 target genes in cucumber inoculated with Foc indicated that JRL3 (Csa2G362470), which is targeted by miR319a, and BEE1 (Csa1G024150), DAHP1 (Csa2G369040), and PERK2 (Csa4G642480), which are targeted by miR6300, are expressed at high levels, but their expression is further up-regulated after Foc inoculation. These results imply that miR319a-JRL3, miR6300-BEE1, miR6300-DAHP1 and miR6300-PERK2 regulate cucumber defenses against FW, and provide the gene resources that may be useful for breeding programs focused on developing new cucumber varieties with enhanced resistance to FW.
Highlights
IntroductionFusarium wilt (FW) of cucumber, which is a typical and destructive soil-borne disease caused by Fusarium oxysporum f
Cucumber (Cucumis sativus L.) is an important vegetable crop cultivated worldwide [1].Fusarium wilt (FW) of cucumber, which is a typical and destructive soil-borne disease caused by Fusarium oxysporum f. sp. cucumerinum (Foc), is one of the major factors restricting global cucumber yield and quality [2,3,4,5].During an infection, Foc penetrates cucumber plants and quickly spreads to the vascular tissues, where it occludes xylem vessels and produces a toxin that kills host cells, leading to FW
Based on the expression verification, we determined that JRL3 (Csa2G362470), which is putatively targeted by miR319a, and BEE1 (Csa1G024150), DAHP1 (Csa2G369040), and PERK2 (Csa4G642480), which are putatively targeted by miR6300, were abundantly expressed, with expression levels that were higher than those in the controls
Summary
Fusarium wilt (FW) of cucumber, which is a typical and destructive soil-borne disease caused by Fusarium oxysporum f. Foc penetrates cucumber plants and quickly spreads to the vascular tissues, where it occludes xylem vessels and produces a toxin that kills host cells, leading to FW. The disease results in the wilting of leaves or even the entire plant, with plant death occurring several days or weeks after infection [6,7]. Fusarium wilt is extremely difficult to control because it can occur during all cucumber growth stages [2]. Foc can survive in the soil, straw or seeds for many years or even decades, leading to long-term disease cycles [8,9].
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