Abstract

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 defense-related, 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 Xocin 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

Abbreviation

HR, Hypersensitive response; DRGs, differentially regulated genes; Xoc,Xanthomonas oryzae pv. Oryzicola; BLS, bacterial leaf streak; R gene, resistance gene; POD, peroxidase; dpi, days post-inoculation; hpi, hours post-inoculation;BAK1, BRASSINOSTEROID INSENSITIVE 1-associated receptor kinase    1  precursor;   PPR,   pentatricopeptide   repeat;;  TFs, transcription factors; TPS, terpene synthase; WAK, wall-associated kinases; cDNA, complementary deoxyribonucleic acid; cRNA, complemenraey ribonucleic acid; GCOS, GeneChip operating software; MAS, molecule annotation system; RT-PCR, real time-polymerase chain reaction; qRT-PCR, quantitative real time-polymerase chain reaction; PR, pathogenesis-related proteins; SAR, systemic acquired resistance;NBS- LRR, nucleotide binding site- leucine rich repeat; dNTP, deoxyribonucleoside triphosphates; NADH, nicotinamide adenine dinucleotide hydride; ABA, abscisic acid; GA, gibberellic acid; SAPK, stress-activated protein kinase; CBS, cystathionine beta-synthase; NAC, nascent polypeptide-associated complex; NAM, no apical meristem; MAPK, mitogen-activated protein kinase.