RESUMEN
Several MADS box gene lineages involved in flower development have undergone duplications that correlate with the diversification of large groups of flowering plants. In the APETALA1 gene lineage, a major duplication coincides with the origin of the core eudicots, resulting in the euFUL and the euAP1 clades. Arabidopsis FRUITFULL (FUL) and APETALA1 (AP1) function redundantly in specifying floral meristem identity but function independently in sepal and petal identity (AP1) and in proper fruit development and determinacy (FUL). Many of these functions are largely conserved in other core eudicot euAP1 and euFUL genes, but notably, the role of APETALA1 as an "A-function" (sepal and petal identity) gene is thought to be Brassicaceae specific. Understanding how functional divergence of the core eudicot duplicates occurred requires a careful examination of the function of preduplication (FUL-like) genes. Using virus-induced gene silencing, we show that FUL-like genes in opium poppy (Papaver somniferum) and California poppy (Eschscholzia californica) function in axillary meristem growth and in floral meristem and sepal identity and that they also play a key role in fruit development. Interestingly, in opium poppy, these genes also control flowering time and petal identity, suggesting that AP1/FUL homologs might have been independently recruited in petal identity. Because the FUL-like gene functional repertoire encompasses all roles previously described for the core eudicot euAP1 and euFUL genes, we postulate subfunctionalization as the functional outcome after the major AP1/FUL gene lineage duplication event.
Asunto(s)
Flores/anatomía & histología , Flores/crecimiento & desarrollo , Frutas/crecimiento & desarrollo , Papaver/anatomía & histología , Papaver/crecimiento & desarrollo , Proteínas de Plantas/metabolismo , Homología de Secuencia de Aminoácido , California , Flores/genética , Flores/ultraestructura , Frutas/genética , Regulación del Desarrollo de la Expresión Génica , Regulación de la Expresión Génica de las Plantas , Silenciador del Gen , Genes de Plantas/genética , Vectores Genéticos/genética , Datos de Secuencia Molecular , Opio , Papaver/genética , Papaver/ultraestructura , Fenotipo , Filogenia , Hojas de la Planta/genética , Proteínas de Plantas/genética , Virus de Plantas/genética , Unión Proteica , Factores de TiempoRESUMEN
MADS-box genes are crucial regulators of floral development, yet how their functions have evolved to control different aspects of floral patterning is unclear. To understand the extent to which MADS-box gene functions are conserved or have diversified in different angiosperm lineages, we have exploited the capability for functional analyses in a new model system, Papaver somniferum (opium poppy). P. somniferum is a member of the order Ranunculales, and so represents a clade that is evolutionarily distant from those containing traditional model systems such as Arabidopsis, Petunia, maize or rice. We have identified and characterized the roles of several candidate MADS-box genes in petal specification in poppy. In Arabidopsis, the APETALA3 (AP3) MADS-box gene is required for both petal and stamen identity specification. By contrast, we show that the AP3 lineage has undergone gene duplication and subfunctionalization in poppy, with one gene copy required for petal development and the other responsible for stamen development. These differences in gene function are due to differences both in expression patterns and co-factor interactions. Furthermore, the genetic hierarchy controlling petal development in poppy has diverged as compared with that of Arabidopsis. As these are the first functional analyses of AP3 genes in this evolutionarily divergent clade, our results provide new information on the similarities and differences in petal developmental programs across angiosperms. Based on these observations, we discuss a model for how the petal developmental program has evolved.
Asunto(s)
Flores/genética , Regulación de la Expresión Génica de las Plantas , Papaver/genética , Proteínas de Plantas/genética , Secuencia de Aminoácidos , Arabidopsis/genética , Secuencia Conservada , Cartilla de ADN , Evolución Molecular , Flores/ultraestructura , Genes Homeobox , Genes de Plantas , Hibridación in Situ , Proteínas de Dominio MADS/genética , Microscopía Electrónica de Rastreo , Datos de Secuencia Molecular , Papaver/clasificación , Papaver/ultraestructura , Petunia/genética , Filogenia , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Alineación de Secuencia , Homología de Secuencia de AminoácidoRESUMEN
Using post-embedding immunogold techniques the cytological localization of the two branchpoint enzymes of isoquinoline biosynthesis, berberine bridge enzyme (BBE) and (S)-tetrahydroprotoberberine oxidase (STOX), was demonstrated. Electron-microscopic examination revealed their exclusive compartmentation within vesicles. After these vesicles have fused with the central vacuole, they release their contents, resulting in a characteristic electron-dense precipitate at the tonoplast. Vesicles of similar structure could be identified in young meristematic tissues of roots or shoots from different Berberis species and Papaver somniferum L. The appearance of electron-dense osmiophilic material is strictly correlated with the alkaloid content of the tissue. Immunocytological staining of P. somniferum tissue with antibodies directed against BBE led to a characteristic labeling of electron-dense aggregates in idioblasts that are not connected to the laticifer system. This localization demonstrates the strictly cytological separation of benzophenanthridine and morphine biosyntheses within this plant.
Asunto(s)
Bencilisoquinolinas , Berberina/análogos & derivados , Berberina/metabolismo , Oxidorreductasas actuantes sobre Donantes de Grupo CH-CH , Oxidorreductasas N-Desmetilantes/metabolismo , Oxidorreductasas/metabolismo , Plantas/metabolismo , Alcaloides/metabolismo , Alcaloides de Berberina/metabolismo , Berberis/citología , Berberis/metabolismo , Berberis/ultraestructura , Células Cultivadas , Eschscholzia/citología , Eschscholzia/metabolismo , Eschscholzia/ultraestructura , Inmunohistoquímica , Isoquinolinas/metabolismo , Microscopía Inmunoelectrónica , Papaver/citología , Papaver/metabolismo , Papaver/ultraestructura , Células Vegetales , Plantas/ultraestructura , Vacuolas/metabolismo , Vacuolas/ultraestructuraRESUMEN
In continuing studies on the metabolic activity of Papaver somniferum, latex has been examined for its enzyme and alkaloidal metabolite content. After an initial centrifugation of latex at 1000g, the pellet which contained a heterogeneous population of dense organelles was further resolved on sucrose gradients. Of the enzymes monitored, acid phosphatase and L-3,4-dihydroxyphenylalanine decarboxylase were found to be in the latex 1000g supernatant, whereas catecholase (polyphenolase) was localized in two distinct organelles within the 1000g sediment. The lighter organelles, sedimenting at 30% sucrose, contained a soluble enzyme which was readily released on organelle plasmolysis, whereas the catecholase found within the heavier organelles, sedimenting at 55-60% sucrose, was membrane bound and showed significant activity only in the presence of Triton X-100. These latter organelles also contained the alkaloids, including morphine and thebaine, and were observed to readily accumulate [14CH3]morphine. The alkaloid precursor, dopamine, was localized in the same dense vesicle fraction as the alkaloids. The rate of uptake of [7-14C]dopamine into these fractions at room temperature, however, was markedly lower than that of morphine. Electron microscopic examination of the organelles of various densities revealed that they possessed different morphology. The results are consistent with the concept that both the 1000g and supernatant fractions of the latex are required for alkaloid biosynthesis and that a subpopulation of dense organelles found in the 1000g sediment have at least a function as a storage compartment for both alkaloids and their catecholamine precursor.