RESUMO
In the barley (Hordeum vulgare) Hooded (Kap) mutant, the duplication of a 305-bp intron sequence leads to the overexpression of the Barley knox3 (Bkn3) gene, resulting in the development of an extra flower in the spikelet. We used a one-hybrid screen to identify four proteins that bind the intron-located regulatory element (Kap intron-binding proteins). Three of these, Barley Ethylene Response Factor1 (BERF1), Barley Ethylene Insensitive Like1 (BEIL1), and Barley Growth Regulating Factor1 (BGRF1), were characterized and their in vitro DNA-binding capacities verified. Given the homology of BERF1 and BEIL1 to ethylene signaling proteins, we investigated if these factors might play a dual role in intron-mediated regulation and ethylene response. In transgenic rice (Oryza sativa), constitutive expression of the corresponding genes produced phenotypic alterations consistent with perturbations in ethylene levels and variations in the expression of a key gene of ethylene biosynthesis. In barley, ethylene treatment results in partial suppression of the Kap phenotype, accompanied by up-regulation of BERF1 and BEIL1 expression, followed by down-regulation of Bkn3 mRNA levels. In rice protoplasts, BEIL1 activates the expression of a reporter gene driven by the 305-bp intron element, while BERF1 can counteract this activation. Thus, BEIL1 and BERF1, likely in association with other Kap intron-binding proteins, should mediate the fine-tuning of Bkn3 expression by ethylene. We propose a hypothesis for the cross talk between the KNOX and ethylene pathways.
Assuntos
Etilenos/metabolismo , Proteínas de Homeodomínio/metabolismo , Hordeum/metabolismo , Íntrons , Proteínas de Plantas/metabolismo , Fatores de Transcrição/metabolismo , Proteínas de Homeodomínio/genética , Hordeum/genética , Dados de Sequência Molecular , Oryza/genética , Filogenia , Proteínas de Plantas/genética , Plantas Geneticamente ModificadasRESUMO
α-Hederin, a natural triterpene saponin and its derivative kalopanaxsaponin I (ksI) exhibit cytotoxicity against various cancer cell lines and IN VIVO tumors. We studied the genetic variants contributing to the activity of these two anticancer compounds. Cell lines derived from 30 trios of European descent (Centre d'Etude du Polymorphisme Human, CEPH; CEU) and 30 trios of African descent (Yoruban, YRI) were used. Cytotoxicity was determined as inhibition of cell growth at increasing concentrations of α-hederin or ksI for 24 h. In comparison to the European, the Yoruban populations revealed a higher sensitivity to α-hederin and to ksI that can be attributed to several unique SNPs. These SNPs are located near 111 and 130 genes in the European and the Yoruban populations, respectively, raising the possibility that some of these genes contribute to the differential sensitivity to these compounds.
Assuntos
População Negra/genética , Neoplasias/genética , Ácido Oleanólico/análogos & derivados , Fitoterapia , Polimorfismo de Nucleotídeo Único , Saponinas/uso terapêutico , População Branca/genética , Animais , Antineoplásicos Fitogênicos/farmacologia , Antineoplásicos Fitogênicos/uso terapêutico , Linhagem Celular Tumoral , Inibidores do Crescimento/farmacologia , Inibidores do Crescimento/uso terapêutico , Humanos , Ativação Linfocitária/genética , Camundongos , Neoplasias/tratamento farmacológico , Nigella/química , Ácido Oleanólico/farmacologia , Ácido Oleanólico/uso terapêutico , Farmacogenética , Extratos Vegetais/farmacologia , Extratos Vegetais/uso terapêutico , Saponinas/farmacologia , SementesRESUMO
Hydroponically cultivated Nigella sativa L. plants treated with methyl jasmonate (MeJA) showed a twelve-fold increase in levels of the monodesmosidic triterpene saponins alpha-hederin and kalopanaxsaponin I (KsI) in the leaves. We will demonstrate that these two saponins accounted for approximately 10% of the dry plant matter, of which 93% was KsI and 7% alpha-hederin. To address the molecular basis of saponin induction by MeJA, we cloned and characterized the beta-amyrin synthase gene (NsbetaAS1) encoding one of the key enzymes in triterpene saponin biosynthesis. As expected, NsbetaAS1 transcription was induced by MeJA and led to the production of beta-amyrin when over-expressed in yeast.
Assuntos
Acetatos/farmacologia , Ciclopentanos/farmacologia , Transferases Intramoleculares/genética , Nigella sativa/metabolismo , Ácido Oleanólico/análogos & derivados , Oxilipinas/farmacologia , Reguladores de Crescimento de Plantas/farmacologia , Proteínas de Plantas/genética , Saponinas/biossíntese , Cromatografia Líquida de Alta Pressão , Transferases Intramoleculares/química , Transferases Intramoleculares/fisiologia , Nigella sativa/efeitos dos fármacos , Nigella sativa/enzimologia , Ácido Oleanólico/biossíntese , Ácido Oleanólico/química , Ácido Oleanólico/isolamento & purificação , Proteínas de Plantas/química , Proteínas de Plantas/fisiologia , Saponinas/química , Saponinas/isolamento & purificação , Transcrição Gênica/efeitos dos fármacos , Leveduras/genéticaRESUMO
Seed plants with compound leaves constitute a polyphyletic group, but studies of diverse taxa show that genes of the class 1 KNOTTED-LIKE HOMEOBOX (KNOX1) family are often involved in compound leaf development. This suggests that knox1 genes have been recruited on multiple occasions during angiosperm evolution (Bharathan et al. in Science 296:1858-1860, 2002). In agreement with this, we demonstrate that the simple leaf of dandelion (Taraxacum officinale Web.) can be converted into a compound leaf by the constitutive expression of heterologous knox1 genes. Dandelion is a rosette plant of the family Asteraceae, characterised by simple leaves with deeply lobed margins and endogenous knox1 gene expression. Transgenic dandelion plants constitutively expressing the barley (Hordeum vulgare L.) hooded gene (bkn3, barley knox3) or the related bkn1 gene, developed compound leaves featuring epiphyllous rosettes. We discuss these results in the context of two current models of compound leaf formation.
Assuntos
Proteínas de Homeodomínio/genética , Folhas de Planta/crescimento & desenvolvimento , Proteínas de Plantas/genética , Taraxacum/crescimento & desenvolvimento , Expressão Gênica , Genes de Plantas , Proteínas de Homeodomínio/metabolismo , Folhas de Planta/anatomia & histologia , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas/anatomia & histologia , Plantas Geneticamente Modificadas/crescimento & desenvolvimento , Plantas Geneticamente Modificadas/metabolismo , Taraxacum/anatomia & histologia , Taraxacum/metabolismoRESUMO
Anatomical modifications and developmental patterns of tobacco (Nicotiana tabacum L.) plants transgenic for the barley (Hordeum vulgare L.) homeo box genes bkn-1 or bkn-3 were analysed and the morphogenetic processes interpreted. No appreciable difference between bkn-1 and bkn-3 transgenic tobacco was observed in the examined transgenic plants. They were dwarfed and developed epiphyllous appendages on all leaves except the cotyledons. Two major categories of epiphyllous structure were recognised: (i) vegetative shoots on juvenile heart-shaped leaves and (ii) inflorescences or flowers on adult lanceolate leaves. Both types of epiphyllous structure originated in the subepidermal layers, either directly from individual meristems or from an expanded meristematic "cushion". Structural analysis confirmed that the occurrence of epiphylls in the tobacco transformants represented a switch from determinate to indeterminate leaf growth and reproduced the phenotype of the barley Hooded mutant, which had earlier been shown to be associated with the bkn-3 gene [K.J. Muller et al. (1995) Nature 374:727-730].