RESUMO
Triacylglycerols (TAG) are the major form of energy storage in plants. TAG are primarily stored in seeds and fruits, but vegetative tissues also possess a high capacity for their synthesis and storage. These storage lipids are essential to plant development, being used in seedling growth during germination, pollen development, and sexual reproduction, for example. TAG are also an important source of edible oils for animal and human consumption, and are used for fuel and industrial feedstocks. The canonical pathway leading to TAG synthesis is the glycerol-3-phosphate, or Kennedy, pathway, which is an evolutionarily conserved process in most living organisms. The enzymatic machinery for synthesizing TAG is well known in several plant species, and the genes encoding these enzymes have been the focus of many studies. Here, we review recent progress on the understanding of evolutionary, functional and biotechnological aspects of the glycerol-3-phosphate pathway enzymes that produce TAG. We discuss current knowledge about their functional aspects, and summarize valuable insights into genetically engineered plants for enhancing TAG accumulation. Also, we highlight the evolutionary history of these genes and present a meta-analysis linking positive selection to gene family and plant diversification, and also to the domestication processes in oilseed crops.
Assuntos
Frutas/enzimologia , Monoéster Fosfórico Hidrolases/metabolismo , Plantas Comestíveis/enzimologia , Sementes/enzimologia , Triglicerídeos/biossíntese , Animais , Biotecnologia , Simulação por Computador , Produtos Agrícolas/enzimologia , Produtos Agrícolas/genética , Evolução Molecular , Frutas/genética , Humanos , Filogenia , Plantas Comestíveis/genética , Plantas Geneticamente Modificadas , Sementes/genéticaRESUMO
BACKGROUND: Use of plant resources and ecosystems practiced by indigenous peoples of Mesoamerica commonly involves domestication of plant populations and landscapes. Our study analyzed interactions of coexisting wild and managed populations of the pitaya Stenocereus pruinosus, a columnar cactus used for its edible fruit occurring in natural forests, silviculturally managed in milpa agroforestry systems, and agriculturally managed in homegardens of the Tehuacán Valley, Mexico. We aimed at analyzing criteria of artificial selection and their consequences on phenotypic diversity and differentiation, as well as documenting management of propagules at landscape level and their possible contribution to gene flow among populations. METHODS: Semi-structured interviews were conducted to 83 households of the region to document perception of variation, criteria of artificial selection, and patterns of moving propagules among wild and managed populations. Morphological variation of trees from nine wild, silviculturally and agriculturally managed populations was analyzed for 37 characters through univariate and multivariate statistical methods. In addition, indexes of morphological diversity (MD) per population and phenotypic differentiation (PD) among populations were calculated using character states and frequencies. RESULTS: People recognized 15 pitaya varieties based on their pulp color, fruit size, form, flavor, and thorniness. On average, in wild populations we recorded one variety per population, in silviculturally managed populations 1.58 ± 0.77 varieties per parcel, and in agriculturally managed populations 2.19 ± 1.12 varieties per homegarden. Farmers select in favor of sweet flavor (71% of households interviewed) and pulp color (46%) mainly red, orange and yellow. Artificial selection is practiced in homegardens and 65% of people interviewed also do it in agroforestry systems. People obtain fruit and branches from different population types and move propagules from one another. Multivariate analyses showed morphological differentiation of wild and agriculturally managed populations, mainly due to differences in reproductive characters; however, the phenotypic differentiation indexes were relatively low among all populations studied. Morphological diversity of S. pruinosus (average MD = 0.600) is higher than in other columnar cacti species previously analyzed. CONCLUSIONS: Artificial selection in favor of high quality fruit promotes morphological variation and divergence because of the continual replacement of plant material propagated and introduction of propagules from other villages and regions. This process is counteracted by high gene flow influenced by natural factors (pollinators and seed dispersers) but also by human management (movement of propagules among populations), all of which determines relatively low phenotypic differentiation among populations. Conservation of genetic resources of S. pruinosus should be based on the traditional forms of germplasm management by local people.
Assuntos
Agricultura/métodos , Cruzamento , Cactaceae/genética , Dieta , Fluxo Gênico , Fenótipo , Plantas Comestíveis/genética , Cactaceae/anatomia & histologia , Cor , Características da Família , Feminino , Frutas , Genética Populacional , Humanos , Entrevistas como Assunto , Masculino , México , Análise Multivariada , Percepção , Plantas Comestíveis/anatomia & histologia , Sementes , PaladarRESUMO
Jatropha curcas L. has been promoted as an oilseed crop for use to meet the increased world demand for vegetable oil production, and in particular, as a feedstock for biodiesel production. Seed meal is a protein-rich by-product of vegetable oil extraction, which can either be used as an organic fertilizer, or converted to animal feed. However, conversion of J. curcas seed meal into animal feed is complicated by the presence of toxins, though plants producing "edible" or "non-toxic" seeds occur in Mexico. Toxins present in the seeds of J. curcas include phorbol esters and a type-I ribosome inactivating protein (curcin). Although the edible seeds of J. curcas are known to lack phorbol esters, the curcin content of these seeds has not previously been studied. We analyzed the phorbol ester and curcin content of J. curcas seeds obtained from Mexico and Madagascar, and conclude that while phorbol esters are lacking in edible seeds, both types contain curcin. We also analyzed spatial distribution of these toxins in seeds. Phorbol-esters were most concentrated in the tegmen. Curcin was found in both the endosperm and tegmen. We conclude that seed toxicity in J. curcas is likely to be due to a monogenic trait, which may be under maternal control. We also conducted AFLP analysis and conclude that genetic diversity is very limited in the Madagascan collection compared to the Mexican collection.
Assuntos
Jatropha/química , Ésteres de Forbol/análise , Plantas Tóxicas/química , Proteínas Inativadoras de Ribossomos Tipo 1/análise , Sementes/química , Análise do Polimorfismo de Comprimento de Fragmentos Amplificados , DNA de Plantas/genética , DNA de Plantas/isolamento & purificação , Eletroforese em Gel de Poliacrilamida , Escherichia coli/genética , Escherichia coli/metabolismo , Variação Genética , Vetores Genéticos/genética , Vetores Genéticos/metabolismo , Jatropha/genética , Madagáscar , México , Ésteres de Forbol/química , Plantas Comestíveis/química , Plantas Comestíveis/genética , Plantas Tóxicas/genética , Proteínas Inativadoras de Ribossomos Tipo 1/química , Sementes/genéticaRESUMO
Diversity of Pink-Pigmented Facultative Methylotrophs (PPFMs) in phyllosphere of cotton, maize and sunflower was determined based on differential carbon-substrate utilization profile and Random Amplified Polymorphic DNA data. Results indicate that six diversified groups of PPFMs are found in these crops. Sunflower and maize phyllosphere harbor four different groups of methylobacteria while cotton has only two groups.
A diversidade de microrganismos metilotróficos facultativos pigmentados (PPFMs) na filosfera de algodão, milho e girassol foi determinada baseada no perfil diferencial de utilização de substratos de carbono e em dados de RAPD. Os resultados indicaram a existência de seis grupos diferentes de PPFMs nessas plantas. As filosferas de girassol e milho apresentaram quatro grupos diferentes de metilobactérias enquanto a de algodão apresentou apenas dois grupos.
Assuntos
Carbono , Técnicas In Vitro , Methylobacterium/genética , Methylobacterium/metabolismo , Plantas Comestíveis/genética , Plantas Comestíveis/metabolismo , Técnica de Amplificação ao Acaso de DNA Polimórfico , Substratos para Tratamento Biológico , Biodiversidade , MétodosRESUMO
The potato (Solanum tuberosum L.) mitochondrial cox3/sdh4/pseudo-cox2 gene cluster has previously been identified by heterologous hybridization using a Marchantia polymorpha sdh4 probe. In our present study we used Southern blotting using sdh4 and cox2 probes to show that the sdh4 and cox2 genes are clustered in the mitochondria of potato, soybean and pea. Northern blotting revealed cotranscription of sdh4 and cox2 in potato but not in cauliflower, indicating that these genes are not clustered in cauliflower. A putative recombination point was detected downstream of the cox2 pseudogene (pseudo-cox2) in potato mitochondrial DNA (mtDNA). This sequence corresponds to a 32 bp sequence which appears to be well-conserved and is adjacent to the terminals of some mitochondrial genes in Citrullus lanatus, Beta vulgaris and Arabidopsis thaliana and is probably involved in the genic rearrangements. It is possible the potato mtDNA pseudo-cox2 gene was generated by recombination during evolution in the same way as that of several other mitochondrial genes and remains as an inactive partial copy of the functional cox2 which was also detected in potato mtDNA.
Assuntos
Ciclo-Oxigenase 2 , DNA Mitocondrial , Solanum tuberosum/genética , Evolução Molecular , Fenótipo , Plantas Comestíveis/genéticaRESUMO
The identification and characterization of differential gene expression from tissues subjected to stress has gained much attention in plant research. The recognition of elements involved in the response to a particular stress enhances the possibility of promoting crop improvement through direct genetic modification. However, the performance of some of the 'first generation' of transgenic plants with the incorporation of a single gene has not always been as expected. These results have stimulated the development of new transgenic constructions introducing more than one gene and capable of modifying complex pathways. Several techniques are available to conduct the analysis of gene regulation, with such information providing the basis for novel constructs specifically designed to modify metabolism. This review deals with techniques that allow the identification and characterization of differentially-expressed genes and the use of molecular pathway information to produce transgenic plants.
Assuntos
Regulação da Expressão Gênica de Plantas , Plantas Comestíveis/genética , Plantas Geneticamente Modificadas/genética , Impressões Digitais de DNA , DNA de Plantas/genética , Regulação da Expressão Gênica de Plantas/genética , Genes de Plantas/genética , Genoma de Planta , Estresse Oxidativo , Plantas Comestíveis/metabolismo , Plantas Geneticamente Modificadas/metabolismoRESUMO
Recently seven National Academies of Science produced a report on transgenic plants and world agriculture. The report provides scientific perspectives to the ongoing public debate about the potential role for transgenic technology in world agriculture. In this article, we develop the themes of the report and emphasize the potential for future genetically modified (GM) crops with a poverty focus, emphasizing the potential of GM resistance to plant parasitic nematodes for subsistence potato farmers in Bolivia. We judge that a range of incremental gains to crop yields from many transgenes are valuable for future world security. We advocate the establishment of a standard that GM crops must achieve before they are both biosafe and appropriate for resource-poor farmers and we believe that the best interests of the poor require biotechnologists to work towards that objective.
Assuntos
Plantas Comestíveis/genética , Agricultura , Biotecnologia , Bolívia , Países em Desenvolvimento , Ecossistema , Engenharia Genética/economia , Humanos , Infecções por Nematoides/prevenção & controle , Doenças das Plantas/genética , Doenças das Plantas/parasitologia , Plantas Geneticamente Modificadas , Pobreza , Segurança , Solanum tuberosum/genética , Solanum tuberosum/parasitologiaRESUMO
An amarantin 11S globulin cDNA encoding one of the most important storage proteins of amaranth seeds, with a high content of essential amino acids, was expressed in Escherichia coli. A good level of expression of recombinant amarantin with a molecular weight of 59 kDa was obtained. The recombinant protein was extracted by ammonium sulfate precipitation and purified to homogeneity using ion-exchange chromatography and reversed phase high-performance liquid chromatography. The expressed protein exhibited electrophoretic, immunochemical, and surface hydrophobicity properties similar to those of native amarantin from amaranth seed. Also, the recombinant protein was refolded in vitro using two different methods.
Assuntos
Globulinas/química , Proteínas de Plantas/química , Plantas Comestíveis/genética , Sementes , Cromatografia Líquida de Alta Pressão/métodos , Clonagem Molecular , DNA Complementar , Escherichia coli , Globulinas/genética , Proteínas de Plantas/genética , Dobramento de Proteína , Proteínas Recombinantes/química , Mapeamento por RestriçãoRESUMO
We investigated gene expression patterns that occur during taro corm development. Two-dimensional gel electrophoresis identified several different prevalent proteins that accumulate during corm development. Microsequencing studies indicated that some of these proteins are related to taste-modifying proteins, such as curculin and miraculin, and proteins found in other storage organs, such as sporamin and the Kunitz trypsin inhibitor. A curculin-encoding cDNA clone, designated as TC1, was identified that corresponds to a highly prevalent 1-kb corm mRNA. The TC1 mRNA accumulates during corm development, is more prevalent in corm apical than basal regions, and is either absent, or present at low concentrations, in other vegetative organs such as the leaf and root. In situ hybridization experiments showed that the TC1 mRNA is highly concentrated in corm storage parenchyma cells and is absent, or present in reduced concentrations, in other corm cells and tissues. Our results show that corm development is associated with the differentiation of specialized cells and tissues, and that these differentiation events are coupled with the temporal and spatial expression of corm-specific genes.