Basil downy mildew, caused by the pathogen Peronospora belbahrii, is a major problem for sweet basil growers worldwide. The genome sequences of both Ocimum basilicum and P. belbahrii were recently completed but extensive transcriptome analysis of this pathosystem has not been completed. RNA sequencing was performed using basil leaf samples collected three and six days after inoculation with sporangia from an Illinois isolate of P. belbahrii and differentially expressed genes were identified. Gene enrichment analysis identified 22 genes that were upregulated at day three, in comparison to mock inoculated leaf samples, that were classified as ‘defense response to oomycetes’; among this group were five orthologues of Arabidopsis thaliana DOWNY MILDEW RESISTANCE 6. During the same time interval, many genes contributing to photosynthesis in the infected leaves were downregulated in comparison to control leaf samples. Many more genes were differentially expressed in the inoculated basil leaves at day six, compared to mock inoculated leaves, as the pathogen began to produce sporangiophores. On days three and six, the pathogen produced high transcript levels of secreted glycoside hydrolases, which likely release sugars from the plant cell walls needed for the growth of the pathogen. These results contribute to a better understanding of the infection process of downy mildew and will aid the development of more effective measures for reducing the severity of the disease.

中文翻译：

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Peronospora belbahrii 和 Ocimum basilicum 在易感相互作用中的双重转录分析

罗勒霜霉病由病原体Peronospora belbahrii引起，是全世界甜罗勒种植者面临的主要问题。Ocimum basilicum和P. belbahrii的基因组序列最近已完成，但尚未完成对该病理系统的广泛转录组分析。使用来自伊利诺伊州P. belbahrii分离株的孢子囊接种后 3 天和 6 天收集的罗勒叶样品进行 RNA 测序，并鉴定出差异表达的基因。基因富集分析确定了 22 个在第 3 天上调的基因，与模拟接种的叶样本相比，这些基因被归类为“对卵菌的防御反应”；这组中有五个直系同源物拟南芥 绒毛霉 抗性 6。在同一时间间隔内，与对照叶片样品相比，受感染叶片中许多有助于光合作用的基因被下调。与模拟接种的叶子相比，在第六天接种的罗勒叶中差异表达更多的基因，因为病原体开始产生孢子囊。在第 3 天和第 6 天，病原体产生高转录水平的分泌型糖苷水解酶，这可能会从病原体生长所需的植物细胞壁释放糖。这些结果有助于更好地了解霜霉病的感染过程，并将有助于制定更有效的措施来降低疾病的严重程度。