Gene Expression profiling of rice leaves undergoing an innate immune response induced by XOO secreted cell wall degrading enzyme LipA (Lipase/Esterase A). Oryza sativa

The plant cell wall degrading enzyme LipA (Lipase/Esterase A) is a Type II secretion system secreted protein of Xanthomonas oryzae pv. oryzae (Xoo; the casual of bacterial leaf blight of rice). LipA is an Xoo virulence factor. However, LipA is a double edged sword for Xoo as it induces rice defense responses such as programmed cell death/hypersensitive response like reaction (HR) and callose deposition. Prior treatment with LipA enhances resistance against subseqent Xoo infection. In order to understand the molecular events associated with Esterase (LipA) induced innate immune responsein rice , whole genome transcriptional profiling was performed using Affymetrix Rice GeneChips Overall design: Leaves of two weeks old green house grown susceptible rice cultivar (Taichung Native-1; TN-1) were infiltrated with either 30-40μl of purified Xoo Lipase/Esterase A (LipA) (500μg/ml) or with buffer (10mM potassium phosphate buffer pH 6.6) alone (as described in Jha et al. 2007; MPMI vol 20, pp 31-40). The plants were shifted to a growth chamber (28oC; 80% relative humidity; 12/12h light/dark cycle) 48 hours before the treatment. 20-30 leaf pieces covering the infiltrated zone from each of the treatments were harvested 12 h after infiltration. Total RNA isolated from the pooled samples was subjected for expression analysis using Affymetrix GeneChip System. The experiment was repeated with three different biological replicates using RNA isolated from three batches of rice leaves treated with the freshly purified Xoo LipA and the buffer.