Abstract
BackgroundCucumber downy mildew is among the most important diseases that can disrupt cucumber production. Propamocarb, also known as propyl-[3-(dimethylamino)propyl]carbamate (PM), is a systemic carbamate fungicide pesticide that is widely applied in agricultural production because of its high efficiency of pathogens control, especially cucumber downy mildew. However, residual PM can remain in cucumbers after the disease has been controlled. To explore the molecular mechanisms of PM retention, cucumber cultivars ‘D9320’ (with the highest residual PM content) and ‘D0351’ (lowest residual PM content) were studied. High-throughput tag-sequencing (Tag-Seq) results showed that the CsDIR16 gene was related to PM residue, which was verified using transgenic technology.ResultsWe investigated the activity of a dirigent cucumber protein encoded by the CsDIR16 in gene response to stress induced by PM treatment. Gene-expression levels of CsDIR16 were up-regulated in the fruits, leaves, and stems of ‘D0351’ plants in response to PM treatment. However, in cultivar ‘D9320’, CsDIR16 levels were down-regulated in the leaves and stems after PM treatment, with no statistically significant differences observed in the fruits. Induction by jasmonic acid, abscisic acid, polyethylene glycol 4000, NaCl, and Corynespora cassiicola Wei (Cor) resulted in CsDIR16 up-regulation in ‘D0351’ and ‘D9320’. Expression after salicylic acid treatment was up-regulated in ‘D0351’, but was down-regulated in ‘D9320’. CsDIR16 overexpression lowered PM residues, and these were more rapidly reduced in CsDIR16(+) transgenic ‘D9320’ plants than in wild-type ‘D9320’ and CsDIR16(−) transgenic plants.ConclusionsAnalyses of the CsDIR16-expression patterns in the cucumber cultivars with the highest and lowest levels of PM residue, and transgenic validation indicated that CsDIR16 plays a positive role in reducing PM residues. The findings of this study help understand the regulatory mechanisms occurring in response to PM stress in cucumbers and in establishing the genetic basis for developing low-pesticide residue cucumber cultivars.
Highlights
Cucumber downy mildew is among the most important diseases that can disrupt cucumber production
Cloning and bioinformatics analysis of CsDIR16 In this study, we investigated a cucumber PM-responsive gene (Csa4M280630.1), designated here as CsDIR16
The full-length complementrary DNA (cDNA) sequences of CsDIR16 were cloned from cucumber fruits of ‘D0351’ and ‘D9320’ by reverse transcription-polymerase chain reaction (PCR) (RT-PCR) (Fig. 1a)
Summary
Cucumber downy mildew is among the most important diseases that can disrupt cucumber production. Propamocarb, known as propyl-[3-(dimethylamino)propyl]carbamate (PM), is a systemic carbamate fungicide pesticide that is widely applied in agricultural production because of its high efficiency of pathogens control, especially cucumber downy mildew. Residual PM can remain in cucumbers after the disease has been controlled. Pesticides are among the most widely used chemicals in the world. With their application in modern agriculture, up to 80% of crop yield were protected from pest and weeds [1]. Pesticide residues represent a major food safety issue. Downy mildew is a devastating disease affecting cucurbits that is caused by infection by zoospores. The associated lesions can induce chlorosis or yellowing, and further
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