Cho Yangrae, Kim Kwang-Hyung, La Rota Mauricio, Scott Derrick, Santopietro Graciela, Callihan Meagan, Mitchell Thomas K, Lawrence Christopher B
Virginia Bioinformatics Institute and Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
Mol Microbiol. 2009 Jun;72(6):1316-33. doi: 10.1111/j.1365-2958.2009.06689.x. Epub 2009 May 13.
Alternaria brassicicola is an important, necrotrophic fungal pathogen that causes black spot disease on Brassicas. In order to study pathogenicity mechanisms, gene deletion mutants were generated for 21 putative regulatory genes including kinases and transcription factors subjectively selected from the annotated A. brassicicola genome. Except for Ste12, the deletion of the SNF1 kinase, XlnR, and CreA homologues that control cell wall-degrading enzyme production did not significantly affect virulence in contrast to other pathogenic fungi. Only deletion of XlnR but not CreA, Ste12 or SNF1 impaired the fungus' ability to utilize sole carbon sources suggesting Alternaria regulates expression of cell wall-degrading enzymes in a novel manner. In addition, two novel virulence factors encoding a transcription factor (AbPro1) and a two-component histidine kinase gene (AbNIK1) were discovered. Deletion of AbPro1 resulted in a 70% reduction in virulence and a 25% reduction in vegetative growth rates in vitro. Deletion of AbNIK1 resulted in a near complete loss of virulence, increased sensitivity to osmotic stress, and no changes in vegetative growth rates in vitro. Interestingly, addition of long polypeptides to spores of both Deltaabste12 and Deltaabnik1 during inoculations resulted in a complete restoration of pathogenicity through a yet to be defined mechanism.
芸苔链格孢是一种重要的坏死性真菌病原体，可引起十字花科植物的黑斑病。为了研究致病机制，针对21个假定的调控基因构建了基因缺失突变体，这些基因包括从已注释的芸苔链格孢基因组中主观选择的激酶和转录因子。除了Ste12外，与其他致病真菌不同，控制细胞壁降解酶产生的SNF1激酶、XlnR和CreA同源物的缺失对毒力没有显著影响。只有XlnR的缺失而非CreA、Ste12或SNF1的缺失损害了真菌利用单一碳源的能力，这表明链格孢以一种新的方式调节细胞壁降解酶的表达。此外，还发现了两个新的毒力因子，一个编码转录因子（AbPro1），另一个编码双组分组氨酸激酶基因（AbNIK1）。AbPro1的缺失导致毒力降低70%，体外营养生长速率降低25%。AbNIK1的缺失导致毒力几乎完全丧失，对渗透胁迫的敏感性增加，体外营养生长速率没有变化。有趣的是，在接种过程中向Deltaabste12和Deltaabnik1的孢子中添加长多肽，通过一种尚未明确的机制导致致病性完全恢复。
