CgSCD1 Is Essential for Melanin Biosynthesis and Pathogenicity of Colletotrichum gloeosporioides

Abstract

<i>Colletotrichum gloeosporioides</i>, an important phytopathogenic fungus, mainly infects tropical fruits and results in serious anthracnose. Previous studies have shown that melanin biosynthesis inhibitor can inhibit the melanization of the appressoria of <i>Magnaporthe grisea</i> and <i>Colletotrichum</i> <i>orbiculare</i>, resulting in limited infection of the hosts. In this study, we identified and characterized a scytalone dehydratase gene (<i>CgSCD1</i>) from <i>C. gloeosporioides</i> which is involved in melanin synthesis. The <i>CgSCD1</i> gene deletion mutant <i>ΔCgscd1</i> was obtained using homologous recombination. The <i>ΔCgscd1</i> mutant showed no melanin accumulation on appressoria formation and vegetative hyphae. Furthermore, the virulence of <i>ΔCgscd1</i> was significantly reduced in comparison with the wild-type (WT) strain. Further investigations showed that the growth rate as well as germination and appressorium formation of <i>ΔCgscd1</i> displayed no difference compared to the wild-type and complemented transformant Cgscd1^com strains. Furthermore, we found that the appressorial turgor pressure in the <i>ΔCgscd1</i> mutant showed no difference compared to that in the WT and Cgscd1^com strains in the incipient cytorrhysis experiment. However, fewer infectious hyphae of <i>ΔCgscd1</i> were observed in the penetration experiments, suggesting that the penetration ability of nonpigmented appressoria was partially impaired. In conclusion, we identified the <i>CgSCD1</i> gene, which is involved in melanin synthesis and pathogenicity, and found that the melanization defect did not affect appressorial turgor pressure in <i>C. gloeosporioides</i>.