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FUNCTIONAL GENOMICS OF PANTOEA STEWARTII SUBSP. STEWARTII AND PARTIAL GENOME SEQUENCE OF THE MAIZE STOLBUR PHYTOPLASMA SOLANI, TWO INSECT-TRANSMITTED BACTERIAL PATHOGENS OF MAIZE

Correa, Valdir Ribeiro, Mr.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1291166530

Abstract Details

2010, Doctor of Philosophy, Ohio State University, Horticulture and Crop Science.
Stewart’s wilt and maize redness (MR), caused by the bacterial pathogens Pantoea stewartii subsp. stewartii (Pnss) and stolbur phytoplasma (Candidatus Phytoplasma solani), are two important diseases of maize. MR, endemic to Eastern Europe, can cause yield losses of 40-90%. Although most U.S. maize hybrids are resistant to Pnss, the disease is important because of strict quarantine restrictions for seed exportation. Moreover, Pnss makes a good model system for bacteria-host interactions due to vast genomic and genetic resources. A better understanding of the biology of these pathogens could provide new avenues for disease management and discovery of key mechanisms of pathogen-host interactions. Gram-negative bacterial pathogens of eukaryotes often secrete effector proteins directly into host cells via a needle-like protein channel called ‘type III secretion system’ (T3SS), and bacteria adapted to either animal or plant hosts use phylogenetically distinct T3SSs for secreting proteins. We found that Pnss carries two type-three secretion systems that enable it to invade both animal and plant hosts. In addition to a Hrp-type T3SS, known to be essential for maize pathogenesis, Pnss has a second T3SS (PSI-2) that is required for persistence in its flea beetle vector, Chaetocnema pulicaria. Mutagenesis of the PSI-2 psaN gene, essential for building the T3SS, greatly reduced Pnss persistence in insect guts, and its transmission to maize. Complementation of the psaN gene reversed these phenotypes. When mechanically inoculated, the Pnss mutant was fully virulent on maize, indicating that PSI-2 is not required for plant pathogenicity. Our findings demonstrate that the two T3SSs in Pnss play different roles in the life cycle of this bacterium as it alternates between insect and plants. Information on stolbur phytoplasma genome sequences regulating host and vector specificity is lacking. It has been shown that the maize-infecting stolbur phytoplasma, transmitted by Reptalus panzeri, causes phenotypically different symptoms on indicator plants, as compared to stolbur normally associated with solanaceous hosts and transmitted by Hyalesthes obsoletus, suggesting genetic differences in its genome. This difference may be linked to a shift in the stolbur population infecting maize and R. panzeri. To address this question and to expand genomic resources for stolbur, we used Illumina® sequencing to obtain sequences of stolbur infected maize plant. About 0.735 Mb of the predicted 0.85 Mb of the stolbur phytoplasma genome was sequenced. The sequence contained 764 predicted open reading frames, with 51% of the protein coding sequences being functionally assigned. Genes known to be present in potential mobile units and genes encoding secreted proteins were identified. Stolbur phytoplasma specific sequences that may be used for diagnostic purposes were also identified. Overall, our findings provide additional information on mechanisms Pnss uses to interact with its insect vector and may prompt the exploration of the life cycle of these and other bacterial pathogens in search of currently unknown alternate host species that in the case of human pathogens is relevant to assess food security. It also provides new genomic resources to better understand stolbur phytoplasma interactions with its plant and insect hosts.
Richard Pratt, PhD (Advisor)
Margaret Redinbaugh, PhD (Committee Co-Chair)
David Mackey, PhD (Committee Member)
Jyan-Chyun Jang, PhD (Committee Member)
154 p.
Plant Pathology
T3SS; effector proteins; Pantoea stewartii; insect vector; colonization; maize stolbur; Illumina; genome sequencing.

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Citations

  • Correa, V. R. (2010). FUNCTIONAL GENOMICS OF PANTOEA STEWARTII SUBSP. STEWARTII AND PARTIAL GENOME SEQUENCE OF THE MAIZE STOLBUR PHYTOPLASMA SOLANI, TWO INSECT-TRANSMITTED BACTERIAL PATHOGENS OF MAIZE [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291166530

    APA Style (7th edition)

  • Correa, Valdir. FUNCTIONAL GENOMICS OF PANTOEA STEWARTII SUBSP. STEWARTII AND PARTIAL GENOME SEQUENCE OF THE MAIZE STOLBUR PHYTOPLASMA SOLANI, TWO INSECT-TRANSMITTED BACTERIAL PATHOGENS OF MAIZE. 2010. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1291166530.

    MLA Style (8th edition)

  • Correa, Valdir. "FUNCTIONAL GENOMICS OF PANTOEA STEWARTII SUBSP. STEWARTII AND PARTIAL GENOME SEQUENCE OF THE MAIZE STOLBUR PHYTOPLASMA SOLANI, TWO INSECT-TRANSMITTED BACTERIAL PATHOGENS OF MAIZE." Doctoral dissertation, Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291166530

    Chicago Manual of Style (17th edition)

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