RESUMO
JASMONATE ZIM-domain (JAZ) proteins act as transcriptional repressors of jasmonic acid (JA) responses and play a crucial role in the regulation of host immunity in plants. Here, we report that OsMYC2, a JAZ-interacting transcription factor in rice (Oryza sativa L.), plays an important role in the resistance response against rice bacterial blight, which is one of the most serious diseases in rice, caused by Xanthomonas oryzae pv. oryzae (Xoo). The results showed that OsMYC2 interacted with some OsJAZ proteins in a JAZ-interacting domain (JID)-dependent manner. The up-regulation of OsMYC2 in response to JA was regulated by OsJAZ8. Transgenic rice plants overexpressing OsMYC2 exhibited a JA-hypersensitive phenotype and were more resistant to Xoo. A large-scale microarray analysis revealed that OsMYC2 up-regulated OsJAZ10 as well as many other defense-related genes. OsMYC2 selectively bound to the G-box-like motif of the OsJAZ10 promoter in vivo and regulated the expression of early JA-responsive genes, but not of late JA-responsive genes. The nuclear localization of OsMYC2 depended on a nuclear localization signal within JID. Overall, we conclude that OsMYC2 acts as a positive regulator of early JA signals in the JA-induced resistance against Xoo in rice.
Assuntos
Oryza/genética , Oryza/microbiologia , Doenças das Plantas/microbiologia , Proteínas de Plantas/genética , Xanthomonas/patogenicidade , Núcleo Celular/metabolismo , Ciclopentanos/metabolismo , Resistência à Doença/genética , Regulação da Expressão Gênica de Plantas , Oxilipinas/metabolismo , Doenças das Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Regulação para CimaRESUMO
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.
Assuntos
Ciclopentanos/farmacologia , Oryza/genética , Oxilipinas/farmacologia , Doenças das Plantas/imunologia , Reguladores de Crescimento de Plantas/farmacologia , Proteínas de Plantas/genética , Xanthomonas/fisiologia , Dimerização , Resistência à Doença , Expressão Gênica , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Análise de Sequência com Séries de Oligonucleotídeos , Oryza/efeitos dos fármacos , Oryza/imunologia , Oryza/microbiologia , Doenças das Plantas/microbiologia , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo , Complexo de Endopeptidases do Proteassoma , Estabilidade Proteica/efeitos dos fármacos , Estrutura Terciária de Proteína , Proteólise/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Técnicas do Sistema de Duplo-Híbrido , Regulação para Cima/efeitos dos fármacosRESUMO
Volatile terpenoids such as monoterpenes and sesquiterpenes play multiple roles in plant responses and are synthesized by terpene synthases (TPSs). We have previously isolated a partial TPS gene, RlemTPS4, that responds to microbial attack in rough lemon. In this study, we isolated a full length RlemTPS4 cDNA from rough lemon. RlemTPS4 localized in the cytosol. The recombinant RlemTPS4 protein was obtained using a prokaryotic expression system and GC-MS analysis of the terpenes produced by the RlemTPS4 enzymatic reaction determined that RlemTPS4 produces some sesquiterpenes such as δ-elemene. The RlemTPS4 gene was specifically expressed in specialized epithelial cells surrounding the oil secretory cavities in rough lemon leaf tissue.
Assuntos
Alquil e Aril Transferases/isolamento & purificação , Citrus/enzimologia , Células Epiteliais/enzimologia , Proteínas de Plantas/isolamento & purificação , Alquil e Aril Transferases/química , Alquil e Aril Transferases/genética , Alquil e Aril Transferases/metabolismo , Sequência de Aminoácidos , Citrus/genética , Regulação da Expressão Gênica de Plantas , Dados de Sequência Molecular , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Análise de Sequência de ProteínaRESUMO
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
Host-selective toxins (HSTs) produced by some strains of Alternaria alternata are selectively toxic to certain cultivars of plants. However, the role of HSTs in toxin-insensitive plants is currently unknown. Here, we studied the role of ACT-toxin using an ACT-toxin producing A. alternata strain SH20 and the ACT-toxin-insensitive plant rough lemon. Induction of some defense related genes in response to SH20 were faster or stronger than in response to the ACT-toxin deficient SH20 mutant. By sequencing subtractive PCR clones obtained from mRNA of rough lemon leaves inoculated with SH20 after subtraction with that of the ACT-toxin deficient SH20 mutant, we isolated the SH20-responsive genes in rough lemon. Among the SH20-responsive genes analyzed in this study, we isolated a terpene synthase (TPS) gene, RlemTPS3. We also determined that RlemTPS3 localizes to the chloroplast and produces the monoterpene geraniol.