RESUMO
Alpha-dioxygenases (α-DOX) catalyzing the primary oxygenation of fatty acids to oxylipins were recently found in plants. Here, the biological roles of the pepper α-DOX (Ca-DOX) gene, which is strongly induced during non-host pathogen infection in chili pepper, were examined. Virus-induced gene silencing demonstrated that down-regulation of Ca-DOX enhanced susceptibility to bacterial pathogens and suppressed the hypersensitive response via the suppression of pathogenesis-related genes such as PR4, proteinase inhibitor II and lipid transfer protein (PR14). Ca-DOX-silenced pepper plants also exhibited more retarded growth with lower epidermal cell numbers and reduced cell wall thickness than control plants. To better understand regulation of Ca-DOX, transgenic Arabidopsis plants harboring the ß-glucuronidase (GUS) reporter gene driven from a putative Ca-DOX promoter were generated. GUS expression was significantly induced upon avirulent pathogen infection in transgenic Arabidopsis leaves, whereas GUS induction was relatively weak upon virulent pathogen treatment. After treatment with plant hormones, early and strong GUS expression was seen after treatment of salicylic acid, whereas ethylene and methyl jasmonate treatments produced relatively weak and late GUS signals. These results will enable us to further understand the role of α-DOX, which is important in lipid metabolism, defense responses, and growth development in plants.
Assuntos
Capsicum/genética , Dioxigenases/genética , Resistência à Doença/genética , Inativação Gênica , Proteínas de Plantas/genética , Sequência de Aminoácidos , Capsicum/microbiologia , Dioxigenases/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Interações Hospedeiro-Patógeno , Microscopia Eletrônica de Transmissão , Doenças das Plantas/genética , Doenças das Plantas/microbiologia , Reguladores de Crescimento de Plantas/farmacologia , Folhas de Planta/genética , Folhas de Planta/microbiologia , Folhas de Planta/ultraestrutura , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Pseudomonas syringae/fisiologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Homologia de Sequência de Aminoácidos , Xanthomonas/fisiologiaRESUMO
Ginseng ESTs allowed us to identify an unknown transcript which is highly abundant in rhizomes and seeds. We called the cDNA ginseng-specific abundant protein (GSAP), and identified three homologues, GSAP1, GSAP2, and GSAP3. GSAP cDNAs encode a small polypeptide consisting of 121 or 117 amino acids, and GSAP3 shows 87.6% amino acid sequence homology with GSAP1. GSAP transcripts were detected in most plant tissues, but GSAP3 is highly expressed in seeds, and is up-regulated under stressed conditions, water deficit. GSAP3-GFP fusion protein is located in the cell wall when expressed in onion epidermis cells. The transgenic Arabidopsis seedlings which over-expressed GSAP3 grew faster than those of the wild-type plant on the medium containing 300 mM mannitol and 100 mM NaCl. GSAP3 may play a role in altering the characteristics of the cell wall to allow for more tolerance of water deficit stress under abiotic stress conditions.
Assuntos
Adaptação Fisiológica , Parede Celular/fisiologia , Estresse Oxidativo/fisiologia , Panax/fisiologia , Proteínas de Plantas/fisiologia , Adaptação Fisiológica/genética , Sequência de Aminoácidos , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/fisiologia , Parede Celular/química , Parede Celular/genética , Desidratação/metabolismo , Dados de Sequência Molecular , Panax/química , Panax/genética , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Isoformas de Proteínas/biossíntese , Isoformas de Proteínas/genética , Isoformas de Proteínas/fisiologiaRESUMO
Methyl jasmonate (MeJA) treatment increases the levels of plant secondary metabolites, including ginsenosides, which are considered to be the main active compounds in ginseng (Panax ginseng C.A. Meyer). To create a ginseng gene resource that contains the genes involved in the biosynthesis of secondary metabolites, including ginsenosides, we generated 3,134 expression sequence tags (ESTs) from MeJA-treated ginseng hairy roots. These ESTs assembled into 370 clusters and 1,680 singletons. Genes yielding highly abundant transcripts were those encoding proteins involved in fatty acid desaturation, the defense response, and the biosynthesis of secondary metabolites. Analysis of the latter group revealed a number of genes that may be involved in the biosynthesis of ginsenosides, namely, oxidosqualene cyclase (OSC), cytochrome P450, and glycosyltransferase. A novel OSC gene was also identified by this analysis. RNA gel blot analysis confirmed that transcription of this OSC gene, along with squalene synthase (SS) and squalene epoxidase (SE) gene transcription, is increased by MeJA treatment. This ginseng EST data set will also provide important information on the genes that are involved in the biosynthesis of other secondary metabolites and the genes that are responsive to MeJA treatment.