RESUMO
In previous reports we have reported that theobroxide induces characteristic accumulation of allene oxide cyclase (AOC; EC 5.3.99.6) protein and jasmonic acid (JA) in Pharbitis nil. In the present study, PnAOC, an AOC gene from Pharbitis nil was cloned. Immunofluorescence assays indicated that the AOC protein is located in the chloroplast of vascular bundles in Pharbitis nil leaves. The PnAOC cDNA sequence lacking the chloroplast signal peptide was successfully expressed in Escherichia coli, and a gas chromatography-mass spectrum assay suggested the relative AOC activity of the recombinant PnAOC protein in comparison with Arabidopsis AOC2. Interestingly, a biphasic expression of PnAOC was induced by theobroxide, which is consistent with the accumulation patterns of AOC protein and JA. All these results indicate that AOC is the primary target of theobroxide regulation and suggest that feedback regulation of PnAOC by JA occurs upon theobroxide treatment in Pharbitis nil.
Assuntos
Cicloexanos/farmacologia , Compostos de Epóxi/farmacologia , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Oxirredutases Intramoleculares/genética , Ipomoea nil/enzimologia , Sequência de Aminoácidos , Cloroplastos/metabolismo , Clonagem Molecular , Escherichia coli/genética , Oxirredutases Intramoleculares/química , Oxirredutases Intramoleculares/metabolismo , Ipomoea nil/citologia , Dados de Sequência Molecular , Filogenia , Folhas de Planta/citologia , Folhas de Planta/enzimologia , Transporte Proteico , RNA Mensageiro/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Petal senescence is a type of programmed cell death (PCD) that is tightly regulated by multiple genes. We recently reported that a putative membrane protein, InPSR26, regulates progression of PCD during petal senescence in Japanese morning glory (Ipomoea nil). Reduced InPSR26 expression in transgenic plants (PSR26r lines) resulted in accelerated petal senescence with hastened development of PCD symptoms, and transcript levels of autophagy-related genes were reduced in the petals. Autophagy visualized by monodansylcadaverine staining indicated reduced autophagic activity in the PSR26r plants. The results from our recent studies suggest that InPSR26 acts to delay the progression of PCD during petal senescence, possibly through regulation of the autophagic process. In this addendum, we discuss the role of autophagy in petal senescence as it relates to these findings.
Assuntos
Apoptose , Autofagia , Senescência Celular , Flores/citologia , Flores/crescimento & desenvolvimento , Ipomoea nil/citologia , Regulação da Expressão Gênica de Plantas , Ipomoea nil/genética , Modelos BiológicosRESUMO
The onset and progression of petal senescence, which is a type of programmed cell death (PCD), are highly regulated. Genes showing changes in expression during petal senescence in Japanese morning glory (Ipomoea nil) were isolated and examined to elucidate their function in PCD. We show here that a putative membrane protein, InPSR26, regulates progression of PCD during petal senescence in Japanese morning glory. InPSR26 is dominantly expressed in petal limbs and its transcript level increases prior to visible senescence symptoms. Transgenic plants with reduced InPSR26 expression (PSR26r lines) showed accelerated petal wilting, with PCD symptoms including cell collapse, ion and anthocyanin leakage, and DNA degradation accelerated in petals compared to wild-type plants. Transcript levels of autophagy- and PCD-related genes (InATG4, InATG8, InVPE, and InBI-1) were reduced in the petals of PSR26r plants. Autophagy visualized by monodansylcadaverine staining confirmed that autophagy is induced in senescing petal cells of wild-type plants and that the percentage of cells containing monodansylcadaverine-stained structures, most likely autophagosomes, was significantly lower in the petals of PSR26r plants, indicating reduced autophagic activity in the PSR26r plants. These results suggest that InPSR26 acts to delay the progression of PCD during petal senescence, possibly through regulation of the autophagic process. Our data also suggest that autophagy delays PCD in petal senescence.
Assuntos
Apoptose/fisiologia , Senescência Celular/fisiologia , Flores/crescimento & desenvolvimento , Ipomoea nil/crescimento & desenvolvimento , Ipomoea nil/genética , Proteínas de Membrana/genética , Proteínas de Plantas/genética , Antocianinas/metabolismo , Flores/genética , Ipomoea nil/citologia , Plantas Geneticamente Modificadas/genética , RNA Mensageiro/genética , RNA de Plantas/genética , Regulação para CimaRESUMO
Circumnutation and winding in plants are universal growth movements that allow plants to survive despite their sessile nature. However, the detailed molecular mechanisms controlling these phenomena remain unclear. We previously found that a gravitropic mutant of Japanese morning glory (Pharbitis nil or Ipomoea nil), Shidare-asagao (weeping), is defective not only in circumnutation but also in the winding response. This phenotype is similar to that of the Arabidopsis SCARECROW (SCR) mutant. We therefore investigated whether morning glory SCR (PnSCR) is involved in the weeping phenotype. We found that one amino acid was inserted into the highly conserved VHIID motif in weeping-type PnSCR; this mutation caused abnormal endodermal differentiation. We introduced either the mutant or WT PnSCR into Arabidopsis scr mutants for complementation tests. PnSCR of the WT, but not of weeping, rescued the shoot gravitropism and circumnutation of scr. These results show that both the abnormal gravitropism and the circumnutation defect in weeping are attributable to a loss of PnSCR function. Thus, our data show that gravisensing endodermal cells are indispensable for shoot circumnutation and the winding response and that PnSCR is responsible for the abnormal phenotypes of weeping.
