Abstract
In rice, plant activator such as benzothiadiazole (BTH) acts on the salicylic acid signaling pathway and thereby transcriptionally upregulates a transcription factor WRKY45 leading to defense induction. Overexpression of WRKY45 (WRKY45-ox) conferred rice with strong resistance against fungal blast (M. grisea) and bacterial leaf-blight (X. oryzae) diseases. To investigate the mechanism underlying the disease resistance conferred by WRKY45, we performed microscopic and microarray analysis in M. grisea-inoculated WRKY45-ox and BTH-treated rice plants.
Upon inoculation of M. grisea to WRKY45-ox rice, strong inhibition of the invasion of fungal penetration peg was observed. Hypersensitive-response-like cell death was also observed where rice cells permitted hyphal invasion. Microarray revealed that the genes for biosynthesis of diterpenoid phytoalexin, momilactone A, upregulated after M. grisea infection in WRKY45-ox rice. The genes were not upregulated in BTH-treated rice plants, but upregulated after M. grisea infection to them. The upregulation was not observed in WRKY45-knockdown rice plants. These results indicate that WRKY45 primes defense genes in BTH-treated rice.
