The Function Analysis Of StLAC2Gene On Melanin Biosynthesis And Pathogenicity In Setosphaeria Turcica

The deletion of key enzyme genes in DHN melanin synthesis pathway leads toSetosphaeria turcica loses pathogenicity. A laccase gene of S.turcica, named StLAC2, wascloned in our laboratory at the earlier research. In order to confirm the function of StLAC2in DHN melanin biosynthesis and pathogenicity, gene knock-out technique was used toconstruct StLAC2gene deleted mutants. The StLAC2gene was identified playing a key roleon melanin biosynthesis and pathogenicity by analyzing the mutants. Main results in thispaper were as follows:1. The pBC-StLAC2gene-disruption vector was constructed using pUCATPH andpBS based on the gene double-cross homologous combination theory.2. The two mutants of StLAC2gene-disruption, named as△StLAC2-1and△StLAC2-2, were obtained by PEG-mediated gene transformation system.3. The mutants△StLAC2-2and△StLAC2-1displayed gray-white colony on PDAmedium, had less melanization and cannot produce conidia. The oxidase activity of laccasein mutants was reduced.4. The hyphae suspension of wild-type isolate and mutants were incubated on thecellophane. The results displayed that the mycelium of wild type produced appressoria,was abled to penetrate cellophane membranes and second hypha could grow undercellophane. The hyphae of mutants could not develop appressorium and penetrated thecellophane membranes. The mutant hyphae only growed on the surface of cellophanemembrane.5. The results of pathogenicity showed that the mutants could not invade the intactmaize leaves, but could infected stabbed corn leaf.Those results showed that laccase gene StLAC2played an important role inconidium formation, melanin synthesis, appressorium development and penetrate thehost epidermis cells.