Rice WRKY45 Plays a Crucial Role in Benzothiadiazole-Inducible Blast Resistance

Abstract

Benzothiadiazole (BTH) is a so-called plant activator and protects plants from diseases by activating the salicylic acid (SA) signaling pathway. By microarray screening, we identified BTH-and SA-inducible WRKY transcription factor (TF) genes that were upregulated within 3 h after BTH treatment. Overexpression of one of them, WRKY45, in rice (Oryza sativa) markedly enhanced resistance to rice blast fungus. RNA interference-mediated knockdown of WRKY45 compromised BTH-inducible resistance to blast disease, indicating that it is essential for BTH-induced defense responses. In a transient expression system, WRKY45 activated reporter gene transcription through W-boxes. Epistasis analysis suggested that WRKY45 acts in the SA signaling pathway independently of NH1, a rice ortholog of Arabidopsis thaliana NPR1, which distinguishes WRKY45 from known Arabidopsis WRKY TFs. Two defense-related genes, encoding a glutathione S-transferase and a cytochrome P450, were found to be regulated downstream of WRKY45 but were not regulated by NH1, consistent with the apparent independence of the WRKY45-and NH1-dependent pathways. Defense gene expression in WRKY45-overexpressed rice plants varied with growth conditions, suggesting that some environmental factor(s) acts downstream of WRKY45 transcription. We propose a role for WRKY45 in BTH-induced and SA-mediated defense signaling in rice and its potential utility in improving disease resistance of rice, an importance food resource worldwide.

Effects of Colonization of a Bacterial Endophyte,Azospirillumsp. B510, on Disease Resistance in Rice

“…The primer pairs previously described were used for other genes in the real-time PCR. 4,20,21) Results Endophytic colonization of Azospirillum sp. B510 To examine the endophytic behavior of Azospirillum sp.…”

“…4,22) To determine the physiological changes in Azospirillum sp. B510-induced disease resistance, we analyzed the expression of pathogenesis-related genes (OsPR-1a, OsPR-1b, OsPR-2, OsPR-4, and PBZ1) and defense-related WRKY45 by quantitative real-time PCR (Fig.…”

“…2) As a form of induced resistance activated by pathogens, systemic acquired resistance induced through the salicylic acid (SA)-mediated signaling pathway has been well characterized in rice as well as in Arabidopsis. 3,4) Recent studies have indicated that nonpathogenic microorganisms such as actinobacterium and rhizobium enhance defense signaling in plants. Wheat-derived Streptomyces sp.…”

Rice RING protein OsBBI1 with E3 ligase activity confers broad-spectrum resistance against Magnaporthe oryzae by modifying the cell wall defence

“…Two R genes, Pi9 and Pi21, confer broad-spectrum resistance against multiple races of M. oryzae [9,10]. Rac GTPasemediated events (e.g., generation of ROS), activation of MAP kinase, and other key components, such as RAR1, SGT1, Hsp90, and WRKY45, play important roles in regulating the immune response against M. oryzae [11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Endogenous SA is involved in defence against M. oryzae [25].…”

Characterization of an Elicitor-Induced Rice WRKY Gene,OsWRKY71

“…7,8) The rice genome is predicted to contain over 100 WRKY (OsWRKY) genes. 9) It has been found that several WRKY genes are expressed in response to the rice blast fungal elicitor 10) and the defense signal molecules salicylic acid and jasmonic acid, 11) and that OsWRKY13 and OsWRKY45 are involved in salicylic acid-mediated defense signaling in rice, 12,13) but the biological functions of most of the WRKY factors in defense signaling in rice remain unknown.…”