Bacillus thuringiensis subsp.yosoo 4CA1 can not produce melanin at 28℃,while it may possess high yield of melanin when induced at 42℃.In order to study the mechanism of melanin production induced by high temperature,a random insertional mutant library of B.thuringiensis subsp.yosoo 4CA1 was constructed with plasmid pIC333 containing the mini-Tn10 transposon.Compared with the wild-type strain 4CA1,a mutant of producing melanintion weakly at 42℃ was obtained.Then the flanking sequence of mini-Tn10 was cloned and sequenced.The results showed that the gene interrupted by mini-Tn10 was sodA2.