Transcriptional profiling of rice gene expression changes upon co-infection with insect Orseola oryza and pathogen Xanthomonas oryzae pv. oryzae that causes gall midge and bacterial blight respectively.

Yield loss in crop plants due to biotic stresses is a major problem and pyramiding of R genes is often suggested for sustained and durable resistance against target pests. Information is available for single R gene interaction in rice and other crop plants, but not much data is available for multiple R gene interaction against multiple pathogens/pests. In this study we carried out transcriptional analysis of two rice lines introgressed with either R gene against bacterial blight and gall midge or, against bacterial blight and fungal blast. The gene expression changes were investigated through microarray and the expression pattern upon co-infection with multiple pathogens was analyzed to study the synergistic effect of R gene mediated defense responses as well as to explore the possibility of any antagonism between the R genes as defense pathway employed due to R gene mediated resistance variesaccording to the attacking pathogen/pest. Keywords: Expression profiling by array For the experiment, 25 day old rice plants (Rice line RPNF05 carrying bacterial blight resistance gene Xa21, xa13, xa5 and gall midge resistance genes Gm1, Gm4, Gm8, gm3) were infected with the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo) and the insect pest Orseolia oryzae that cause bacterial blight and gall midge respectively. Thereafter, total RNA was isolated from tissue samples that were collected from control (uninfected) and treated plants (infected with pathogen and pest) at 24 and 72 hours post inoculation. The RNA sample from the two time points were pooled and used for expression analysis using Affymetrix GeneChip System. Three biological replicates were used for the experiment.