Abstract
Cucumber (Cucumis sativus L.) is an important vegetable crop worldwide, and Fusarium wilt (FW), caused by Fusarium oxysporum f. sp. cucumerinum (Foc), severely restricts cucumber growth and yield. Accumulating lines of evidence indicate that chitinases play important roles in attacking the invading fungal pathogens through catalyzing their cell wall degradation. Here, we identified the chitinase (Chi) genes in cucumber and further screened the FW-responsive genes via a comparative transcriptome analysis and found that six common genes were predominantly expressed in roots but also significantly upregulated after Foc infection. Expression verification further conformed that Chi2 and Chi14 were obviously induced by Foc as well as by hormone treatments, compared with the controls. The purified Chi2 and Chi14 proteins significantly affected the growth of Foc in vitro, compared with the controls. Knockdown of Chi2 in cucumber by virus-induced gene silencing (VIGS) increased susceptibility to FW, compared with the Chi14-silenced and control plants, and silencing of Chi2 drastically impaired gene activation in the jasmonic acid pathway, suggesting that the Chi2 gene might play positive roles in cucumber FW defense and, therefore, can provide a gene resource for developing cucumber-FW-resistance breeding programs.
Highlights
Cucumber (Cucumis sativus L.) is an economically vegetable crop and cultivated worldwide [1]
We identified 27 chitinase genes (Chis) with verified domains, and these genes were matched to 6 scaffolds in cucumber, except in chromosome 7, and preferentially named from
10 Chis were predominantly expressed in root tissue of cucumber, which is the first tissue that soil-borne pathogens contact and invade [29,30]
Summary
Cucumber (Cucumis sativus L.) is an economically vegetable crop and cultivated worldwide [1]. Cucumber FW is usually considered one of the most significant biotic factors limiting global cucumber output and quality, resulting in the wilting of leaves, or even the entire plant, and plant death within several days or weeks after pathogen infection [7]. This disease can hazard the entire growth and development stages of cucumber [3]. Using resistant cultivars to mine more disease resistance genes and investigate disease resistance mechanisms is recognized as the most sustainable way to control FW disease
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