Abstract
Sulfur (S) fumigation is a commonly used sterilization method in horticultural facilities against fungal diseases. S fumigation damaged cucumber leaves, although the response mechanism is unclear. This study analyzes the growth, transcriptome, and metabolomic profiles of young and mature leaves, ovaries, and commercial cucumber fruits to decipher the mechanism of cucumber stress response under S fumigation. S fumigation significantly changed the photosynthetic efficiency and reactive oxygen species (ROS) in leaves, but not fruit development, fruit mass, and peel color. Transcriptome analysis indicated that S fumigation strongly regulated stress defense genes. The weighted gene co-expression network analysis revealed that S fumigation regulated ASPG1, AMC1 defense genes, LECRK3, and PERK1 protein kinase. The abscisic acid (ABA)-mediated model of regulation under S fumigation was constructed. Metabolome analysis showed that S fumigation significantly upregulated or downregulated the contents of amino acids, organic acids, sugars, glycosides, and lipids (VIP > 1 and P-value < 0.05). The opposite Pearson’s correlations of these differential metabolites implied that cucumber had different metabolic patterns in short-term and long-term S fumigation. Besides, the elevated levels of proline and triglyceride indicated that stress-responsive mechanisms existed in S-fumigated cucumber. Moreover, the comprehensive analysis indicated that S fumigation elevated secondary S-containing metabolites but decreased sulfate absorption and transportation in cucumber. Overall, our results provided a comprehensive assessment of S fumigation on cucumber, which laid the theoretical foundation for S fumigation in protected cultivation.
Highlights
Cucumber (Cucumis sativus L.) is a widely cultivated and popular vegetable worldwide (Li et al, 2019)
Our results provided a comprehensive assessment of S fumigation on cucumber, which laid the theoretical foundation for S fumigation in protected cultivation
S fumigation slightly but insignificantly decreased the Fv/Fm value (Figure 1C). These results indicated that the effects of S fumigation on the photosynthetic system are greater in L12, compared with L0
Summary
Cucumber (Cucumis sativus L.) is a widely cultivated and popular vegetable worldwide (Li et al, 2019). Cucumbers are generally cultivated in protective environments with low light, high humidity, and low temperatures (Singh et al, 2017), conducive for breeding and spreading various fungal diseases. S fumigation with temperature-controlled fumigators is a commonly used sterilization method in horticultural facilities (West and Menzies, 2002). Previous studies demonstrated that S fumigation effectively prevents breeding and spreading powdery mildew, angular spot, and downy mildew in horticultural production (Koller, 2011; Gardner-Gee, 2013; Wright et al, 2015). The current hypothesis suggests that fine particles formed by heating S at high temperatures (190◦C) perform Brownian motion in the air, penetrate the fungus, and inhibit mitochondrial respiration (Cooper and Williams, 2004; Raymond and Brown, 2015). There is multisite contact activity in S action to make the lower risk of pathogen resistance (Raymond and Gillian, 2014; Branham et al, 2020)
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