Botany and Plant Pathology Seminar Series
Speaker: Mr. Bemnet Mengesha - Department of Botany & Plant Pathology - Purdue University
Topic: Mechanisms of tomato basal resistance to fungal infection
When: Wednesday, November 06, 2013 at 3:30 pm in WSLR 116

We study plant resistance to the fungal pathogens Botrytis cinerea and Alternaria solani. To identify new sources of resistance, a collection of tomato related wild Solanum species were evaluated for responses to A. solani and B. cinerea. Among eight wild Solanum species, Solanum lycopersicoides (Slo) was highly resistant to both pathogens with very limited disease symptoms. With the goal of identifying genes that regulate Slo resistance to these pathogens, basal and pathogen induced gene expression profile of Slo was studied through analysis of RNA-seq data. Functionally diverse genes including pathogenesis related proteins, protein kinases, and genes involved in the synthesis of secondary metabolites were induced in response to B. cinerea. Among genes significantly up-regulated early during infection, Slo cytoplasmic receptors like kinases (RLCKs) were selected for further studies due to their potential role in pathogen response signaling. Virus induced gene silencing (VIGS) based reverse genetic screen was initiated to identify RLCKs that impact plant resistance. A previously uncharacterized tomato RLCK was identified based on its impact on B. cinerea resistance in the VIGS screen.  This new RLCK was designated TPK1b related kinase 1 (TRK1) due to its functional and structural similarity to TPK1b, a previously studied RLCK known to contribute to pathogen and insect resistance. Slo TRK1 and the orthologous tomato gene are both induced by B. cinerea and A. solani and share >98% identity. Thus, the follow up studies were performed in tomato due to its better amenability to VIGS than Slo plants. Recombinant TRK1 has autophosporylation and transphosporylation activities in vitro. In addition, TRK1 localizes to the plasma membrane suggesting its contribution early in the plant response pathway. Suppression of TRK1 through VIGS as well as through RNA interference (RNAi) in tomato transgenic plants resulted in increased susceptibility to B. cinerea infection confirming the contribution of TRK1 to resistance. In sum, this study identified genes involved in resistance to necrotrophic fungal pathogens which will be used to further dissect molecular mechanisms of resistance.


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