Effects of Carbon, Nitrogen, Ambient pH and Light on Mycelial Growth, Sporulation, Sorbicillinoid Biosynthesis and Related Gene Expression in Ustilaginoidea virens

Abstract

Sorbicillinoids are a class of hexaketide metabolites produced by Ustilaginoidea virens (teleomorph: Villosiclava virens), an important fungal pathogen that causes a devastating rice disease. In this study, we investigated the effects of environmental factors, including carbon and nitrogen sources, ambient pH and light exposure, on mycelial growth, sporulation, as well as the accumulation of sorbicillinoids, and the expression of related genes involved in sorbicillinoid biosynthesis. It was found that the environmental factors had great influences on mycelial growth and sporulation of U. virens. Fructose and glucose, complex nitrogen sources, acidic conditions and light exposure were favorable for sorbicillinoid production. The relative transcript levels of sorbicillinoid biosynthesis genes were up-regulated when U. virens was separately treated with those environmental factors that favored sorbicillinoid production, indicating that sorbicillinoid biosynthesis was mainly regulated at the transcriptional level by different environmental factors. Two pathway-specific transcription factor genes, UvSorR1 and UvSorR2, were found to participate in the regulation of sorbicillinoid biosynthesis. These results will provide useful information to better understand the regulation mechanisms of sorbicillinoid biosynthesis, and be conducive to develop effective means for controlling sorbicillinoid production in U. virens.

A Genome-Wide Comparison of Rice False Smut Fungus Villosiclava virens Albino Strain LN02 Reveals the Genetic Diversity of Secondary Metabolites and the Cause of Albinism

“…Some secondary metabolite BGCs might be in the silent state. In order to unlock these cryptic gene clusters, a variety of strategies could be used, such as one strain many compounds (OSMAC) method, by changing cultivation parameters (i.e., carbon source, nitrogen source, light intensity, ambient pH, shaking, aeration, incubation temperature, redox status, and metal ions) [41,42], global regulation [43,44], epigenetic manipulation [45,46], and gene cluster heterologous expression [47,48].…”

“…A gradient elution program eluting from 10% to 100% MeOH over 45 min was used, and the flow rate was 1.0 mL/min. The column temperature was set at 30 • C. The wavelength was either set at 290 nm for detection of ustilaginoidins [25] or set at 370 nm for detection of sorbicillinoids [42].…”