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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Crop Bioprotection Research » Research » Publications at this Location » Publication #387483
Research Project: Development of New Production Methodologies for Biocontrol Agents and Fastidious Microbes to Improve Plant Disease Management

Location: Crop Bioprotection Research

Title: Dual transcriptional analysis of Peronospora belbahrii and Ocimum basilicum in susceptible interactions

Author
item Johnson, Eric
item Kim, Hye-Seon
item TIAN, MIAOYING - University Of Hawaii
item DUDAI, NATIV - Agricultural Research Organization Of Israel
item TAL, OFIR - Agricultural Research Organization Of Israel
item GONDA, ITAY - Agricultural Research Organization Of Israel

Submitted to: bioRxiv
Publication Type: Pre-print Publication
Publication Acceptance Date: 9/7/2021
Publication Date: 9/7/2021
Citation: Johnson, E.T., Kim, H., Tian, M., Dudai, N., Tal, O., Gonda, I. 2021. Dual transcriptional analysis of Peronospora belbahrii and Ocimum basilicum in susceptible interactions. bioRxiv. 2021. Article 457810. https://doi.org/10.1101/2021.09.07.457810.
DOI: https://doi.org/10.1101/2021.09.07.457810

Interpretive Summary: Downy mildew damages susceptible basil cultivars every year in the United States. The pathogen responsible for downy mildew disease on basil has not been well studied at the molecular level, primarily because the pathogen will not grow on artificial growth medium, but only on living plants. This report is the first to identify a large set of basil genes that are expressed in susceptible leaves in response to basil downy mildew three and six days after inoculation. Surprisingly, a number of potential plant defense genes were upregulated at these time points in response to the pathogen. Many genes contributing to efficient photosynthesis were downregulated at these time points. The downy mildew pathogen infecting the leaves expressed high levels of genes coding for enzymes that likely degrade plant cell walls, which provides energy for the pathogen. These results improve our knowledge of the infection process of basil downy mildew and could aid the development of more effective measures for reducing the severity of the disease.

Technical Abstract: 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.