Institute of Biotechnology, Zhejiang University, Hangzhou 310058, China.
Boyce Thompson Institute, Cornell University, Ithaca 14850, USA.
Sci Rep. 2016 Sep 1;6:32437. doi: 10.1038/srep32437.
The tangerine pathotype of Alternaria alternata produces the A. citri toxin (ACT) and is the causal agent of citrus brown spot that results in significant yield losses worldwide. Both the production of ACT and the ability to detoxify reactive oxygen species (ROS) are required for A. alternata pathogenicity in citrus. In this study, we report the 34.41 Mb genome sequence of strain Z7 of the tangerine pathotype of A. alternata. The host selective ACT gene cluster in strain Z7 was identified, which included 25 genes with 19 of them not reported previously. Of these, 10 genes were present only in the tangerine pathotype, representing the most likely candidate genes for this pathotype specialization. A transcriptome analysis of the global effects of H2O2 on gene expression revealed 1108 up-regulated and 498 down-regulated genes. Expressions of those genes encoding catalase, peroxiredoxin, thioredoxin and glutathione were highly induced. Genes encoding several protein families including kinases, transcription factors, transporters, cytochrome P450, ubiquitin and heat shock proteins were found associated with adaptation to oxidative stress. Our data not only revealed the molecular basis of ACT biosynthesis but also provided new insights into the potential pathways that the phytopathogen A. alternata copes with oxidative stress.
橘生炭疽菌产生的柑橘炭疽菌毒素（ACT）是导致柑橘褐斑病的病原菌，该病在全球范围内造成了严重的产量损失。ACT 的产生和对活性氧（ROS）的解毒能力是炭疽菌在柑橘中致病所必需的。在这项研究中，我们报告了橘生炭疽菌的 Z7 菌株的 34.41 Mb 基因组序列。鉴定了 Z7 菌株中宿主特异性的 ACT 基因簇，其中包括 25 个基因，其中 19 个以前没有报道过。其中，10 个基因仅存在于橘生炭疽菌中，这是该生境专化性的最可能候选基因。对 H2O2 对基因表达全局影响的转录组分析显示，有 1108 个上调基因和 498 个下调基因。编码过氧化氢酶、过氧化物酶、硫氧还蛋白和谷胱甘肽的基因表达被高度诱导。与适应氧化应激相关的基因编码了包括激酶、转录因子、转运蛋白、细胞色素 P450、泛素和热休克蛋白在内的几种蛋白家族。我们的数据不仅揭示了 ACT 生物合成的分子基础，还为植物病原菌炭疽菌应对氧化应激的潜在途径提供了新的见解。
