Abstract
Sclerotial development is a vital stage in the life cycles of many fungal plant pathogens. In this study, the protein Ss-CAD, which contains three conserved domains of cinnamyl alcohol dehydrogenase (CAD), was found to be required for sclerotial development in Sclerotinia sclerotiorum. Ss-CAD was significantly upregulated during early stage of sclerotial development. In Ss-CAD-silenced strains, sclerotial development was abnormal. In these silenced strains, formation of sclerotia was delayed or sclerotia yield was reduced, whereas hyphal growth and virulence were normal. Nox1, Nox2, and NoxR, which encode reactive oxygen species (ROS)-generating NADPH oxidases, were downregulated in Ss-CAD-silenced strains. NoxR-silenced strains displayed similar defects during sclerotial formation as Ss-CAD-silenced strains. Treatment of Ss-CAD-silenced strains with exogenous oxidants or NADPH restored normal sclerotial development. Sclerogenesis in Ss-CAD-silenced strains could also be recovered through Nox1 overexpression. The results suggest that Ss-CAD is linked to the NADPH oxidase pathways to affect sclerotial development in S. sclerotiorum.
Highlights
Sclerotinia sclerotiorum (Lib.) de Bary is a globally distributed necrotrophic fungal pathogen
Ss-cinnamyl alcohol dehydrogenase (CAD) is highly expressed at the initiation stage of sclerotial development and its downregulation impairs this process Quantitative real-time reverse-transcription PCR was performed to identify Ss-CAD transcript profiles at various stages of mycelial growth on potato dextrose agar (PDA)
Ss-CAD expression peaked on the third day after inoculation, at which point sclerotial development began
Summary
Sclerotinia sclerotiorum (Lib.) de Bary is a globally distributed necrotrophic fungal pathogen. It infects more than 450 plant species across 75 families and causes significant yield losses in oilseeds such as rape, sunflower, and soybean (Boland and Hall 1994; Hegedus and Rimmer 2005; Bolton et al 2006). The sclerotia of S. sclerotiorum can survive in the soil for more than 8 years and protect this fungus against low temperatures, low moisture, high UV, and microbial activity (Bolton et al 2006). An earlier study demonstrated that several environmental factors, such as nutrition, light, pH, temperature, and oxidative stress, are associated with sclerotial development (Chet and Henis 1975). Numerous recent studies focusing on the molecular mechanisms underlying sclerotial development have revealed that several genes regulate the process
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