African Journal of Biotechnology

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Different patterns of gene expression in rice varieties undergoing a resistant or susceptible interaction with the bacterial leaf streak pathogen

MR Xu, CMV Cruz, BY Fu, LH Zhu, YL Zhou, ZK Li


The rice line carrying the nonhost gene Rxo1, which was cloned from maize, exhibits a rapid hypersensitive response (HR) to Xanthomonas oryzae pv. oryzicola (Xoc). In this study, a microarray experiment was carried out to analyze the genome-wide gene expression responses to Xoc at the early stage in the rice transgenic line and its wild type. 175 and 379 differentially regulated genes (DRGs) were detected in 9804-Rxo1 and 9804 at 36 h post-inoculation (hpi), respectively. The patterns of DRGs induced by Xoc in the transgenic rice line and its wild type were distinctly different: 92.00% of the DRGs were up-regulated in inoculated 9804-Rxo1 and 48.22% of the DRGs were sorted as defense-related genes. In contrast, 40.69% of the DRGs were up-regulated in inoculated 9804 and 40.00% were sorted as injury-induced genes. Some genes specifically up-regulated in infected 9804-Rxo1 were defenserelated, including the genes encoding pathogenesis-related protein, terpene synthase family, transcription factors (TFs) AP2 domain containing protein, myb-like deoxyribonucleic acid (DNA)- binding domain containing protein, and C2H2-type zinc-finger transcription factors. Six peroxidase (POD) genes were significantly up-regulated and POD activity consistently rose in the inoculated 9804- Rxo1, whereas seven POD genes were down-regulated in its wild type, indicating that POD may also play a role in the complex process of resistant response to Xoc in the transgenic line. Instead of focusing only on the R-gene-mediated defense, this study also discusses the susceptible response in the wild types to virulent pathogen infection in transcription level.

Key words: Rice bacterial leaf streak, nonhost resistance, expression profile, Rxo1.
AJOL African Journals Online