The Mechanism Of StPP2A-c Gene Regulating The Pathogenicity In Setosphaeria Turcica

Setosphaeria turcica, an important fungal pathogen, gives rise to a serious threat to cornproduction. At present, lots of researches found that signal transduction pathway could regulate thegrowth, development and pathogenesis of pathogenic fungi. Type2A phosphoprotein phosphatase(PP2A) which locates in the downstream signal transduction pathways is a major Ser/Thr phosphatase.In the signal transduction, the enzyme cascade interacts with other phosphorylases and kinases toregulate the activity of target proteinsIn our previous research, we have used the2A type protein phosphatase gene from S. turcica toconstruct knock-out vector of catalytic subunit of the protein phosphatase gene (StPP2A-c), aiming toidentify its regulatory role in the pathogenicity of S. turcica. The specific inhibitor, construction ofStPP2A-c gene-deletion mutants were used to identify the function of StPP2A-c and the expirementalresults were as follows:1. Cantharidin could significantly inhibit colony growth, conidial germination, appressorialproduction of S. turcica and promote conidiation and the biosynthesis of intracellular melanin.2. With the PEG mediated transformation method, StPP2A-c gene knock-out vector and the RNAivector were respectively transfered into the protoplast of S. turcica. We finally acquired two strains ofgene-deletion mutants and five strains of RNAi transformants by screening with hygromycin resistance,detecting of PCR, Southern bolt and RT-PCR.3. Compared with the wild-type strains, the transformants displayed slower radial growth. Moreover,the colonial color of the gene-deletion mutants was darker than that of the wild-type strain. The mutantshad less aerial mycelia, and the colonial border was not normal. The amount of condia and the contentof the intracellular melanin in mutants were higher than that in the wild-type strain. The results wereconsistent with expirement results of the specific inhibitor test. Among all the data, it was concludedthat the StPP2A-c gene negatively regulated condial development and the DHN melanin biosynthesis inS. turcica. In the penetration assay, mutants could form appressoria on the surface of artificialcellophane. Compared with the wild-type strain, mutants displayed a delay when forming appressoriaand producing invasive hyphae that could penetrate the artificial cellophane. The typicaldiamond-shaped lesions caused by transformants were more serious than those caused by wild-typestrain. Furthermore, the histopathologic observation showed that mutants and wild-type strain all could intrude into the host. Compared to the wild-type strain, the activity of HT-toxin of mutants was notobviously changed. At the same time, the pathogenicity of mutants was stronger than that of wild-typestrain, while the activities of cell wall degredation enzymes of all strains were similar. It was supposedthat the effect of StPP2A-c on sporulation was stronger than that on appressorium formation andinvasived, as well as other virulence factors. As a result, StPP2A-c mainly impacted the pathogenicityby negatively regulating the sporulation of S. turcica.