Abstract:

【Objective】 The objective of this study is to reveal the bacterial gene expression profiling of Xanthomonas oryzae pv. oryzae (Xoo) in rice leaves at early infection stages via DNA expression microarray analysis. 【Method】 A computer-based algorithm for prediction of the minimal number of primers to specifically anneal to all genes in the genome (genome-directed primers, GDPs) of KACC10331, a genome sequenced strain of Xoo was used. Seventy-four oligonucleotides (8 mer in length each) priming all genes in the genome were predicted and used. A set of microarray of 371 pathogenicity-related genes was hybridized with the GDPs-primed and fluorescent Cy3/Cy5-labeled cDNAs, which were reverse-transcribed from RNAs isolated from rice leaves 1d, 3d and 7d post-inoculation of Xoo. 【Result】 The differential expression profiling of pathogenicity-related genes of Xoo at different early infection stages was found. Forty-two, fifty-one and thirty-three genes of Xoo were differentially expressed in the rice leaf tissues at 1 d, 3 d and 7 d after bacterial inoculation relative to the nutrition rich media NBY, respectively. Among them, 5 up-regulated genes and 5 down-regulated genes were observed in Xoo at all early infection stages. The expression of Xoo genes might be related to bacterial invasion, adaptation, proliferation and appearance of symptom. 【Conclusion】 The approach of selective transcript labeling with GDPs for in planta gene expression profiling of Xoo is reported for the first time. The differentially-expressed genes of Xoo might be the candidate targets for the further functional analysis.

Key words: Xanthomonas oryzae pv. oryzae, GDPs, early infection stages, gene expression profiling, differentially-expressed genes