RESUMO
Enzyme 12-oxophytodienoate (OPDA) reductase (EC1.3.1.42), which is involved in the biosynthesis of jasmonic acid (JA), catalyses the reduction of 10, 11-double bonds of OPDA to yield 3-oxo-2-(2'-pentenyl)-cyclopentane-1-octanoic acid (OPC-8:0). The rice OsOPR1 gene encodes OPDA reductase (OPR) converting (-)-cis-OPDA preferentially, rather than (+)-cis-OPDA, a natural precursor of JA. Here, we provide evidence that an OPR family gene in rice chromosome 8, designated OsOPR7, encodes the enzyme involved in the JA biosynthesis. Recombinant OsOPR7-His protein efficiently catalysed the reduction of both enantiomers of cis-OPDA, similar to the OPR3 protein in Arabidopsis thaliana (L.) Heynh. The expression of OsOPR7 mRNA was induced and reached maximum levels within 0.5 h of mechanical wounding and drought stress, and the endogenous JA level started to increase in accordance with the increase in OsOPR7 expression. The GFP-OsOPR7 fusion protein was detected exclusively in peroxisomes in onion epidermal cells. Furthermore, complementation analysis using an Arabidopsis opr3 mutant indicated that the OsOPR7 gene, but not OsOPR1, was able to complement the phenotypes of male sterility in the mutant caused by JA deficiency, and that JA production in the opr3 mutant was also restored by the expression of the OsOPR7 gene. We conclude that the OsOPR7 gene encodes the enzyme catalysing the reduction of natural (+)-cis-OPDA for the JA biosynthesis in rice.
Assuntos
Adaptação Fisiológica , Ciclopentanos/metabolismo , Oryza/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/genética , Oxilipinas/metabolismo , Peroxissomos/metabolismo , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Expressão Gênica , Teste de Complementação Genética , Oryza/metabolismo , Oryza/fisiologia , Oxirredutases/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Infertilidade das Plantas/fisiologia , Folhas de Planta/metabolismo , Estereoisomerismo , Água/fisiologiaRESUMO
The rice 12-oxophytodienoic acid reductase 1 gene (OsOPR1), isolated as a jasmonic acid (JA)-responsive gene, has been suggested to be involved in defense responses in rice. We identified a 19-base pair region that is essential to the JA-responsiveness of OsOPR1 by deletion and mutation analysis of the promoter by dual luciferase assay. This region contains possible recognition sites for basic leucine zipper transcription factors.
Assuntos
Ciclopentanos/farmacologia , Oryza/fisiologia , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/metabolismo , Oxilipinas/farmacologia , Oryza/efeitos dos fármacos , Oryza/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/genética , Regiões Promotoras Genéticas , Elementos de RespostaRESUMO
In suspension-cultured rice ( Oryza sativaL.) cells, jasmonic acid (JA) functions as a signal transducer in elicitor N-acetylchitoheptaose-induced phytoalexin production. Differential screening of a cDNA library constructed using poly(A)(+) RNA from suspension-cultured rice cells treated with JA (10(-4) M) for 2 h yielded a cDNA for a gene that responded to exogenous JA by an increase in mRNA level. Nucleotide sequence analysis indicated that the cDNA encodes an homologue of the yeast Old Yellow Enzyme. The deduced amino acid sequence was very similar to the sequences of 12-oxophytodienoic acid reductases (OPR) 1 and 2 from Arabidopsis thaliana(AtOPR1 and AtOPR2) and OPR1 from tomato ( Lycopersicon esculentum) (LeOPR1). The cDNA-encoded protein purified from recombinant Escherichia coli cells as a hexahistidine-tagged fusion protein exhibited OPR activity similar to that of AtOPR1, AtOPR2, and LeOPR1, which catalyze reduction of (-)- cis-12-oxophytodienoic acid (OPDA) preferentially over (+)- cis-OPDA, a natural precursor of JA. Thus the rice enzyme was termed OsOPR1. The physiological roles of OsOPR1 are discussed. This is the first report of the cloning of an OPR gene from a monocot plant.
Assuntos
Ciclopentanos/farmacologia , Oryza/genética , Oxirredutases atuantes sobre Doadores de Grupo CH-CH , Oxirredutases/genética , Reguladores de Crescimento de Plantas/farmacologia , Células Cultivadas , Clonagem Molecular , Cicloeximida/farmacologia , DNA Complementar/química , DNA Complementar/genética , Ácidos Graxos Insaturados/farmacologia , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Dados de Sequência Molecular , Oryza/citologia , Oryza/efeitos dos fármacos , Oxirredutases/metabolismo , Oxilipinas , Filogenia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , RNA Mensageiro/efeitos dos fármacos , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Análise de Sequência de DNARESUMO
Two cDNA clones for jasmonic acid (JA)-responsive genes, RRJ1 and RRJ2, were isolated by differential screening from suspension-cultured rice cells treated with JA for 2 h. The putative RRJ1 protein is completely identical to that of a putative rice cystathionine gamma-lyase, while the putative RRJ2 protein is highly similar in sequence to a rice pyruvate decarboxylase, PDC1.
