The single functional blast resistance gene Pi54 activates a complex defence mechanism in rice

The Pi54 gene (Pi-k(h)) confers a high degree of resistance to diverse strains of the fungus Magnaporthe oryzae. In order to understand the genome-wide co-expression of genes in the transgenic rice plant Taipei 309 (TP) containing the Pi54 gene, microarray analysis was performed at 72 h post-inoculation of the M. oryzae strain PLP-1. A total of 1154 differentially expressing genes were identified in TP-Pi54 plants. Of these, 587 were up-regulated, whereas 567 genes were found to be down-regulated. 107 genes were found that were exclusively up-regulated and 58 genes that were down- regulated in the case of TP-Pi54. Various defence response genes, such as callose, laccase, PAL, and peroxidase, and genes related to transcription factors like NAC6, Dof zinc finger, MAD box, bZIP, and WRKY were found to be up-regulated in the transgenic line. The enzymatic activities of six plant defence response enzymes, such as peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, β-glucosidase, β-1,3-glucanase, and chitinase, were found to be significantly high in TP-Pi54 at different stages of inoculation by M. oryzae. The total phenol content also increased significantly in resistant transgenic plants after pathogen inoculation. This study suggests the activation of defence response and transcription factor-related genes and a higher expression of key enzymes involved in the defence response pathway in the rice line TP-Pi54, thus leading to incompatible host-pathogen interaction.