RESUMO
Rice is one of the most important crops worldwide, and it is a model for molecular studies of monocotyledonous species, particularly for understanding the molecular mechanisms of plant disease resistance. Jasmonic acid (JA) is an important plant hormone involved in rice-pathogen interactions. In addition, JA-induced volatiles are known to be involved in the rice defense system regulated by JA signaling. In this study, we isolated a JA-induced terpene synthase from rice, and found that it produces two sesquiterpenes; ß-elemene and ß-bisabolene. Furthermore, ß-elemene exhibited significant antifungal activity against Magnaporthe oryzae; however it did not exhibited any antibacterial activity against Xanthomonas oryzae pv. oryzae. JA-induced accumulation of ß-elemene was regulated by OsJAZ8, a rice jasmonate ZIM-domain (JAZ) protein that is involved in the JA signaling pathway, suggesting that ß-elemene plays an important role in JA-induced resistance, and that it functions as an antifungal compound in rice.
Assuntos
Magnaporthe/efeitos dos fármacos , Oryza/enzimologia , Oryza/microbiologia , Alquil e Aril Transferases/genética , Alquil e Aril Transferases/metabolismo , Sequência de Aminoácidos , Antifúngicos/farmacologia , Ciclopentanos/metabolismo , Ciclopentanos/farmacologia , Escherichia coli/genética , Cromatografia Gasosa-Espectrometria de Massas , Dados de Sequência Molecular , Oryza/efeitos dos fármacos , Oryza/genética , Oxilipinas/metabolismo , Oxilipinas/farmacologia , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Xanthomonas/efeitos dos fármacosRESUMO
Jasmonic acid (JA) and salicylic acid (SA) play important roles in plant defense systems. JA and SA signaling pathways interact antagonistically in dicotyledonous plants, but, the status of crosstalk between JA and SA signaling is unknown in monocots. Our rice microarray analysis showed that more than half of the genes upregulated by the SA analog BTH are also upregulated by JA, suggesting that a major portion of the SA-upregulated genes are regulated by JA-dependent signaling in rice. A common defense system that is activated by both JA and SA is thus proposed which plays an important role in pathogen defense responses in rice.
Assuntos
Ciclopentanos/metabolismo , Oryza/imunologia , Oxilipinas/metabolismo , Oryza/metabolismo , Ácido Salicílico/metabolismo , Xanthomonas/imunologiaRESUMO
The plant hormone jasmonic acid (JA) has a crucial role in both host immunity and development in plants. Here, we report the importance of JA signaling in the defense system of rice. Exogenous application of JA conferred resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) in rice. Expression of OsJAZ8, a rice jasmonate ZIM-domain protein, was highly up-regulated by JA. OsJAZ8 interacted with a putative OsCOI1, which is a component of the SCF(COI1) E3 ubiquitin ligase complex, in a coronatine-dependent manner. OsJAZ8 also formed heterodimers with other OsJAZ proteins but did not form homodimer. JA treatment caused OsJAZ8 degradation and this degradation was dependent on the 26S proteasome pathway. Furthermore, the JA-dependent OsJAZ8 degradation was mediated by the Jas domain. Transgenic rice plants overexpressing OsJAZ8ΔC, which lacks the Jas domain, exhibited a JA-insensitive phenotype. A large-scale analysis using a rice DNA microarray revealed that overexpression of OsJAZ8ΔC altered the expression of JA-responsive genes, including defense-related genes, in rice. Furthermore, OsJAZ8ΔC negatively regulated the JA-induced resistance to Xoo in rice. On the basis of these data, we conclude that JA plays an important role in resistance to Xoo, and OsJAZ8 acts as a repressor of JA signaling in rice.
