RESUMO
In cotton plant, Xanthomonas-induced hypersensitive response (HR) is accompanied by a lipid peroxidation process involving a 9-lipoxygenase (LOX), GhLox1. Initiation of this oxidative metabolism implies the release of the LOX substrates, or polyunsaturated fatty acids. Since patatin-like proteins (PLPs) are likely candidates for mediating the latter step, we searched for genes encoding such enzymes, identified and cloned one of them that we named GhPat1. Biochemical and molecular studies showed that GhPat1 expression was up-regulated during the incompatible interaction, prior to the onset of the corresponding galactolipase activity and cell death symptoms in tissues. Protein sequence analysis and modelling also revealed that GhPat1 catalytic amino acids and fold were conserved across plant PLPs. Based on these results and our previous work (Jalloul et al. in Plant J 32:1-12, 2002), a role for GhPat1, in synergy with GhLox1, during HR-specific lipid peroxidation is discussed.
Assuntos
Hidrolases de Éster Carboxílico/metabolismo , Morte Celular , Gossypium/genética , Proteínas de Plantas/metabolismo , Xanthomonas campestris/patogenicidade , Sequência de Aminoácidos , Sequência de Bases , Hidrolases de Éster Carboxílico/genética , Clonagem Molecular , DNA Complementar/genética , Etiquetas de Sequências Expressas , Perfilação da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Gossypium/metabolismo , Gossypium/microbiologia , Dados de Sequência Molecular , Proteínas de Plantas/genética , Estrutura Terciária de Proteína , RNA de Plantas/genética , Alinhamento de Sequência , Análise de Sequência de ProteínaRESUMO
Hypersensitive reaction (HR) cell death of cotton to the incompatible race 18 from Xanthomonas campestris pathovar malvacearum (Xcm) is associated with 9S-lipoxygenase activity (LOX) responsible for lipid peroxidation. Here, we report the cloning of cotton (Gossypium hirsutum L.) LOX gene (GhLOX1) and the sequencing of its promoter. GhLOX1 was found to be highly expressed during Xcm induced HR. Sequence analysis showed that GhLOX1 is a putative 9-LOX, and GhLOX1 promoter contains SA and JA responsive elements. Investigation on LOX signalisation on cotyledons infiltrated with salicylic acid (SA), or incubated with methyl-jasmonate (MeJA) revealed that both treatments induced LOX activity and GhLOX1 gene expression. HR-like symptoms were observed when LOX substrates were then injected in treated (MeJA and SA) cotyledons or when Xcm compatible race 20 was inoculated on MeJA treated cotyledons. Together these results support the fact that GhLOX1 encodes a 9 LOX whose activity would be involved in cell death during cotton HR.
Assuntos
Gossypium/genética , Lipoxigenase/genética , Lipoxigenase/fisiologia , Xanthomonas/metabolismo , Acetatos/metabolismo , Sequência de Aminoácidos , Sequência de Bases , Cotilédone/metabolismo , Ciclopentanos/metabolismo , Regulação da Expressão Gênica de Plantas , Gossypium/metabolismo , Peróxido de Hidrogênio/química , Lipoxigenase/metabolismo , Dados de Sequência Molecular , Oxilipinas/metabolismo , Filogenia , Folhas de Planta/metabolismo , Regiões Promotoras Genéticas , Ácido Salicílico/farmacologia , Homologia de Sequência de AminoácidosRESUMO
It is by now well established that plants use various strategies to defend themselves against herbivores. Besides conventional weapons such as spines and stinging hairs and sophisticated chemical defenses, plants can also involve the enemies of the herbivores in their defense. It has been suggested that plants could even use entomopathogens as part of their defense strategies. In this paper, we show that Brassica oleraceae plants that are attacked by Myzus persicae aphids infected with an entomopathogenic parvovirus (M. persicae densovirus) transport the virus through the phloem locally and systematically. Moreover, healthy aphids that fed on the same leaf, but separated from infected aphids were infected via the plant. Hence, this is proof of the principle that plants can be vectors of an insect virus and can possibly use this virus as a defense against herbivores.
