Abstract: The present invention cloned melanin biosynthesis genes encoding polyketide synthase (PKS), scytalone dehydratase (SCD) and 1.3.8-trihydroxynaphthalene reductase (THN) from the dematiaceous Alternasia alternate into plasmid pCAMBIA1300, followed by transformation of the plasmid into Matarhizium anisopliae via Agrobacterium tumefaciens-mediated transformation. The transformant was able to express the abovementioned genes and synthesize melanin, which then showed enhanced UV tolerance. The transcription and expression of these melanin genes were confirmed in several pathways. The tolerances toward UV radiation, drought and high temperature were increased significantly in these transformants. In addition, the host insects were more susceptible to these transformants under UV radiation.