Apprehending the mechanisms of plant defense subsequent to Bactericera cockerelli feeding and ‘Candidatus Liberibacter solanacearum’ infection

Plants have evolved sophisticated defense mechanisms in response to insect herbivory and pathogen infection. When under attack, plants may respond by eliciting specific responses through different signal transduction pathways. These pathways are regulated by the genes responsible for the production of phytohormones that signal the induction of defensive chemicals and enzymes. Thus, studying plant defense pathways and plant induced response to insect herbivory and pathogen infection may shed a new light on integrated pest management and pathogen control. In this study, we investigated plant induced response to Bactericera cockerelli (potato psyllid) feeding and ‘Candidatus Liberibacter solanacearum’ (CLs) infection. Potato psyllid is an important pest that vectors CLs, a bacterium infecting solanaceous plants and causing the emerging Zebra Chip disease in potatoes. By imposing psyllid herbivory and CLs infection on tomato plants (Solanum lycopersicum cv. Money Maker), we were able to (1) determine specific genes that were elicited by plant as immune response and (2) examine the induction of genes that regulate the expression of anti-nutritive enzymes. Here, we looked for specific gene expression in plants that had no psyllid (control), in plants fed by psyllids not harboring CLs, and in plants fed by psyllids harboring and transmitting CLs. After 3 days of feeding period, all 20 psyllid nymphs on each plant were removed. The plants and psyllids were tested and confirmed for infection prior to collecting plant tissues to test for gene expression by qRT-PCR. The result indicated that CLs infection and psyllid feeding induced plant immunity and caused specific effects on subsequent plant responses.