1a. Objectives (from AD-416):
1. Cloning and functional determination of virulent genes of Candidatus Liberibacter solanacearum. 2. Construct and evaluate transgenic potato to suppress putative virulent genes of Candidatus Liberibacter solanacearum.
1b. Approach (from AD-416):
1. Establish ZC-infected plants through graft inoculation (or by psyllid transmission) and conduct the pathogenicity evaluation ZC-infected potato plants under greenhouse and field growing conditions (by collaborator). 2. Perform genome wide sequence analysis, identify and clone virulent genes of Candidatus Liberibacter solanacearum (by ARS Scientist). 3. Conduct molecular characterization and functional analyses of target genes using a heterologous gene expression system (by ARS Scientist). 4. Develop and evaluate zebra chip resistant potato through antisense and/or RNAi techniques (by collaborator and ARS scientist).
3. Progress Report:
This research is in support of objective 2 (Elucidate molecular interactions of plant hosts and bacterial pathogens) of the in-house project. Zebra chip (ZC), an economically important disease of potato is caused by ‘Candidatus Liberibacter solanacearum’ (Lso). While the causal agent has been identified, factors associated with severity of ZC are largely unknown. The goal of this project is to develop a novel technique to suppress key virulence genes of the pathogen to mitigate ZC disease. With the availability of genome sequences of the bacterium, virulence genes involved in zinc transport, iron transport accumulation system (ITA) and salicylate hydroxylase were identified. Laboratory expression assays were developed to characterize these virulence determinants. The assays provided insight into function of candidate genes associated with pathogenicity. These approaches will permit evaluation of potato in response to ZC.