RESUMO
Resumen La micrografía analítica es una herramienta útil para la identificación de restos vegetales en muestras de material trozado o molido que no podrían ser identificadas de forma morfológica. El objetivo de este estudio es conocer los caracteres mi- crográficos de las semillas de Cebil (Anadenanthera colubrina var. cebil (Griseb.) Altschul, Leguminosae) y Chamico (Datura ferox L., Solanaceae), con el fin de proporcionar parámetros empleables para su identificación en un contexto forense y toxicológico. Los caracteres micrográficos relacionados con el tegumento exterior y las esclereidas fueron los más indicados para diferenciar entre ambas especies.
Abstract Analytical micrography is a useful tool for the identification of plant parts that can't be identified for its morphological characters. The aim of this work is to obtain micrographic characters of Cebil (Anadenanthera colubrina var. cebil (Griseb.) Altschul, Leguminosae) and Chamico (Datura ferox L., Solanaceae) seeds for its identification in a toxicological and forensic context. The most suitable micrographic features were the ones related with exterior testa and the stone cells.
Assuntos
Sementes/citologia , Solanaceae/citologia , Alucinógenos , Fabaceae/citologia , Argentina , Intoxicação por Plantas/diagnóstico , Fotomicrografia/métodosRESUMO
Indeterminate root growth depends on the stem cell niche (SCN) and root apical meristem (RAM) maintenance whose regulation permits plasticity in root system formation. Using a forward genetics approach, we isolated the moots koom1 ('short root' in Mayan) mutant that shows complete primary RAM exhaustion and abolished SCN activity. We identified that this phenotype is caused by a point mutation in the METHIONINE OVERACCUMULATOR2 (MTO2) gene that encodes THREONINE SYNTHASE1 and renamed the mutant as mto2-2. The amino acid profile showed drastic changes, most notorious of which was accumulation of methionine. In non-allelic mto1-1 (Arabidopsis thaliana cystathionine gamma-synthetase1) and mto3-1 (S-adenosylmethionine synthetase) mutants, both with an increased methionine level, the RAM size was similar to that of the wild type, suggesting that methionine overaccumulation itself did not cause RAM exhaustion in mto2 mutants. When mto2-2 RAM is not yet completely exhausted, exogenous threonine induced de novo SCN establishment and root growth recovery. The threonine-dependent RAM re-establishment in mto2-2 suggests that threonine is a limiting factor for RAM maintenance. In the root, MTO2 was predominantly expressed in the RAM. The essential role of threonine in mouse embryonic stem cells and in RAM maintenance suggests that common regulatory mechanisms may operate in plant and animal SCN maintenance.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismo , Meristema/citologia , Meristema/metabolismo , Nicho de Células-Tronco/fisiologia , Proteínas de Arabidopsis/genética , Regulação da Expressão Gênica de Plantas/genética , Regulação da Expressão Gênica de Plantas/fisiologia , Mutação/genética , Sementes/citologia , Sementes/metabolismo , Transdução de Sinais/genética , Transdução de Sinais/fisiologiaRESUMO
Catechins, including catechin (C) and epicatechin (E), are the main type of flavonoids in cacao seeds. They play important roles in plant defense and have been associated with human health benefits. Although flavonoid biosynthesis has been extensively studied using in vitro and in vivo models, the regulatory mechanisms controlling their accumulation under light/dark conditions remain poorly understood. To identify differences in flavonoid biosynthesis (particularly catechins) under different light treatments, we used cacao cell suspensions exposed to white-blue light and darkness during 14 days. RNA-Seq was applied to evaluate differential gene expression. Our results indicate that light can effectively regulate flavonoid profiles, inducing a faster accumulation of phenolic compounds and shifting E/C ratios, in particular as a response to switching from white to blue light. The results demonstrated that HY5, MYB12, ANR and LAR were differentially regulated under light/dark conditions and could be targeted by overexpression aiming to improve catechin synthesis in cell cultures. In conclusion, our RNA-Seq analysis of cacao cells cultured under different light conditions provides a platform to dissect key aspects into the genetic regulatory network of flavonoids. These light-responsive candidate genes can be used further to modulate the flavonoid production in in vitro systems with value-added characteristics.
Assuntos
Cacau/genética , Catequina/biossíntese , Flavonoides/biossíntese , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/genética , Sementes/genética , Fatores de Transcrição/genética , Cacau/citologia , Cacau/metabolismo , Cacau/efeitos da radiação , Catequina/genética , Flavonoides/genética , Redes Reguladoras de Genes , Luz , Fotoperíodo , Células Vegetais/metabolismo , Células Vegetais/efeitos da radiação , Proteínas de Plantas/classificação , Proteínas de Plantas/metabolismo , Sementes/citologia , Sementes/metabolismo , Sementes/efeitos da radiação , Análise de Sequência de RNA , Fatores de Transcrição/classificação , Fatores de Transcrição/metabolismo , TranscriptomaRESUMO
Toxicity by aluminum is a growth-limiting factor in plants cultivated in acidic soils. This metal also promotes signal transduction pathways leading to the biosynthesis of defense compounds, including secondary metabolites. In this study, we observed that Coffea arabica L. cells that were kept in the dark did not produce detectable levels of caffeine. However, irradiation with light and supplementation of the culture medium with theobromine were the best conditions for cell maintenance to investigate the role of aluminum in caffeine biosynthesis. The addition of theobromine to the cells did not cause any changes to cell growth and was useful for the bioconversion of theobromine to caffeine. During a short-term AlCl3-treatment (500µM) of C. arabica cells kept under light irradiation, increases in the caffeine levels in samples that were recovered from both the cells and culture media were evident. This augmentation coincided with increases in the enzyme activity of caffeine synthase (CS) and the transcript level of the gene encoding this enzyme (CS). Together, these results suggest that actions by Al and theobromine on the same pathway lead to the induction of caffeine biosynthesis.
Assuntos
Alumínio/toxicidade , Cafeína/metabolismo , Coffea/efeitos dos fármacos , Células do Mesofilo/efeitos dos fármacos , Raízes de Plantas/efeitos dos fármacos , Sementes/efeitos dos fármacos , Poluentes do Solo/toxicidade , Processos de Crescimento Celular/efeitos dos fármacos , Processos de Crescimento Celular/efeitos da radiação , Linhagem Celular , Células Cultivadas , Coffea/citologia , Coffea/metabolismo , Coffea/efeitos da radiação , Meios de Cultivo Condicionados/química , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Luz , Células do Mesofilo/citologia , Células do Mesofilo/metabolismo , Células do Mesofilo/efeitos da radiação , Metiltransferases/química , Metiltransferases/genética , Metiltransferases/metabolismo , Proteínas de Plantas/agonistas , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raízes de Plantas/citologia , Raízes de Plantas/metabolismo , Raízes de Plantas/efeitos da radiação , RNA Mensageiro/metabolismo , RNA de Plantas/metabolismo , Sementes/citologia , Sementes/metabolismo , Sementes/efeitos da radiação , Teobromina/metabolismo , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/efeitos da radiaçãoRESUMO
Wheat seeds infected with Pyrenophora tritici-repentis, the causal agent of tan spot, are partially responsible for outbreaks caused by this pathogen. Seed lots with a high incidence of P. tritici-repentis must be rapidly acquired for transmission and pathogen-control studies. Therefore, the aim of this study was to determine whether changes in water potential of culture medium and variations in inoculation time might favor the infection of wheat seeds by P. tritici-repentis without compromising seed viability. Colonies of P. tritici-repentis were grown on potato-dextrose-agar (PDA) culture medium, adjusted to a water potential of -0.36 MPa, under water stress induced by mannitol at potentials of -0.4, -0.6, -0.8, -1.0, and -1.2 MPa. Analyses were carried out to determine mycelial growth index and seed exposure time to the culture medium to start germination as a function of water potential. Afterwards, wheat seeds were placed in contact with colonies of P. tritici-repentis for 24, 48, and 72 hours at potentials of -0.4, -0.6, -0.8, -1.0, and -1.2 MPa. The experiment was arranged in a completely randomized design, in a factorial scheme (water potential × inoculation time). Rates of germination, seedling emergence in soil, and seed infection were assessed. Mycelial growth was stimulated at lower water potentials, which germinated faster. A 24-hour inoculation time and a -0.4 MPa water potential were efficient toinfect wheat seeds with P. tritici-repentis, without hindering seedling germination and emergence underlaboratory conditions.(AU)
Sementes de trigo infectadas com Pyrenophora tritici-repentis, agente causal da mancha-amarela da folha, respondem em parte pelas epidemias causadas por este patógeno. A obtenção rápida de lotes de sementes com alta incidência de P. tritici-repentis é fundamental para estudos de transmissão e controle. Sendo assim, o objetivo deste trabalho foi verificar se alterações no potencial hídrico do meio de cultura e variações na duração da inoculação podem favorecer a infecção de sementes de trigo por P. tritici-repentis, sem comprometer a viabilidade destas sementes. Colônias do patógeno foram cultivadas sobre meio de cultura batata-dextrose-ágar (BDA) básico, no potencial hídrico de -0,36 MPa, e no meio BDA com restrição hídrica, causada pela adição de manitol, nos potenciais hídricos de -0,4, -0,6, -0,8, -1,0 e -1,2 MPa. Foram realizadas análises para determinar o índice de crescimento micelial do fungo e o tempo de exposição das sementes ao meio de cultura para o início do processo germinativo em função dos potenciais hídricos. Posteriormente, sementes de trigo foram colocadas em contato com as colônias de P. tritici-repentis durante 24, 48 e 72 horas nos potenciais hídricos de -0,4, -0,6, -0,8, -1,0 e -1,2 MPa, em esquema fatorial (potenciais hídricos x duração da inoculação) e delineamento inteiramente casualizado. Foram avaliadas as taxas de germinação, de emergência de plântulas em condições de laboratório.(AU)
Assuntos
Sementes/citologia , Sementes/crescimento & desenvolvimento , Fungos/enzimologia , Fungos/crescimento & desenvolvimento , Planejamento Hídrico/análise , Inoculantes Agrícolas/químicaRESUMO
Little information is currently available concerning the mechanisms controlling palm seed germination. We compared the anatomical and physiological aspects of seeds of two neotropical palm species showing different levels of dormancy. The seeds of Attalea vitrivir and Butia capitata were evaluated for the endogenous contents of hormones (ABA, GAs, CKs, BRs, IAA, JA, SA and the ethylene precursor ACC) in their cotyledonary petiole and operculum (structures involved in germination control), the force necessary to displace the operculum, endo-ß-mannanase activities, and embryo cell elongation. The analyses were carried out on with intact dry and imbibed seeds as well as with seeds with the operculum mechanically removed, 2, 5 and 10 days after sowing. The germinabilities of the intact seeds of A. vitrivir and B. capitata were 68% and 3%, respectively; the removal of the operculum increased germination to more than 90% in both species. Reductions of ABA and increases in GAs contents coincided with cell elongation, although there is no evidence that hormonal balance and endo-ß-mannanase activity are involved in operculum weakening. The ratio between the embryo length and the force required for operculum displacement (EL/OF) was found to be 1.9 times greater in A. vitrivir than in B. capitata, which means that very small elongations in each cell would be sufficient to promote germination, resulting in a lower level of dormancy in the former species. EL/OF and cell growth control are therefore important for defining dormancy level in palm seeds.
Assuntos
Germinação/fisiologia , Magnoliopsida/crescimento & desenvolvimento , Reguladores de Crescimento de Plantas/metabolismo , Sementes/metabolismo , Magnoliopsida/citologia , Sementes/citologia , Especificidade da EspécieRESUMO
Pera is a neotropical genus that currently belongs to the family Peraceae. This circumscription resulted from an inclusion of the Rafflesiaceae between the old tribe Pereae and all other Euphorbiaceae, and wherein Pereae was elevated to family rank making Euphorbiaceae monophyletic again. These changes are necessary although Rafflesiaceae are holoparasitic with extremely reduced vegetative bodies and large flowers while Peraceae and Euphorbiaceae have well developed vegetative parts and reduced flowers. As the embryology of Peraceae was poorly known, and embryological processes are conservative, we studied the embryology of Pera glabrata, searching for similarities between Peraceae, Rafflesiaceae, and Euphorbiaceae that could support this grouping. Usual methods of light microscopy and scanning electron microscopy were utilised. The results show endothecium with reversed-T-shaped cells, prismatic crystals in the tapetum, and disintegrated aerenchymatous septum in the mature fruit as unique features for Peraceae and possibly apomorphies for the family. In addition to the unisexual flowers, porogamous fertilization is present and one ovule per carpel which may support the Peraceae-Rafflesiaceae-Euphorbiaceae clade. The comparative approach also suggests possible (syn-)apomorphies for linoids and phyllanthoids, only linoids, Rafflesiaceae, Euphorbiaceae, and Ixonanthaceae. The presence of a placental obturator found previously unknown in Peraceae emerged as a possible synapomorphy for the euphorbioids (including Ixonanthaceae, Linaceae, Phyllanthaceae, Picrodendraceae, Peraceae, Rafflesiaceae, and Euphorbiaceae), which appeared in a common ancestor of the group and has been lost in Rafflesiaceae.
Assuntos
Magnoliopsida/classificação , Evolução Biológica , Classificação , Euphorbiaceae/classificação , Euphorbiaceae/citologia , Euphorbiaceae/embriologia , Euphorbiaceae/genética , Flores/classificação , Flores/citologia , Flores/embriologia , Flores/genética , Magnoliopsida/citologia , Magnoliopsida/embriologia , Magnoliopsida/genética , Sementes/classificação , Sementes/citologia , Sementes/embriologia , Sementes/genéticaRESUMO
Trichloris crinita is a perennial forage grass species native to arid regions of the American continent. Due to its extensive area of distribution, good forage quality and resistance to drought and grazing, this species is widely utilised as forage and for revegetation purposes in environments with low water availability. Despite its importance, genetic improvement of T. crinita has been very limited, partly as consequence of the lack of knowledge on its mode of reproduction. In the present work, we studied the reproductive biology of T. crinita by means of embryological analyses, flow cytometric seed screen (FCSS), self-compatibility tests and progeny testing with morphological and molecular markers. Cytological analyses revealed embryo sacs with eight nuclei and of Polygonum type for all T. crinita accessions analysed. FCSS histograms exhibited two clear peaks corresponding to 2C and 3C DNA content, indicating embryo sacs of sexual origin. Controlled pollination experiments designed to evaluate seed set (%) demonstrated that T. crinita is self-compatible, whereas results from morphological and simple sequence repeat (SSR) marker analysis of progeny revealed lack of outcrossing. Together, these results indicate that T. crinita reproduces sexually. It is a self-compatible and autogamous species. It is expected that these data will have a positive impact in the genetics and breeding of this species, and therefore contribute to its proper utilisation in arid regions.
Assuntos
Poaceae/fisiologia , Sementes/citologia , Animais , Citometria de Fluxo , Flores/fisiologia , Heterozigoto , Endogamia , Repetições de Microssatélites , Poaceae/genética , Polinização , Sementes/fisiologia , AutofertilizaçãoRESUMO
Wheat seeds infected with Pyrenophora tritici-repentis, the causal agent of tan spot, are partially responsible for outbreaks caused by this pathogen. Seed lots with a high incidence of P. tritici-repentis must be rapidly acquired for transmission and pathogen-control studies. Therefore, the aim of this study was to determine whether changes in water potential of culture medium and variations in inoculation time might favor the infection of wheat seeds by P. tritici-repentis without compromising seed viability. Colonies of P. tritici-repentis were grown on potato-dextrose-agar (PDA) culture medium, adjusted to a water potential of -0.36 MPa, under water stress induced by mannitol at potentials of -0.4, -0.6, -0.8, -1.0, and -1.2 MPa. Analyses were carried out to determine mycelial growth index and seed exposure time to the culture medium to start germination as a function of water potential. Afterwards, wheat seeds were placed in contact with colonies of P. tritici-repentis for 24, 48, and 72 hours at potentials of -0.4, -0.6, -0.8, -1.0, and -1.2 MPa. The experiment was arranged in a completely randomized design, in a factorial scheme (water potential × inoculation time). Rates of germination, seedling emergence in soil, and seed infection were assessed. Mycelial growth was stimulated at lower water potentials, which germinated faster. A 24-hour inoculation time and a -0.4 MPa water potential were efficient toinfect wheat seeds with P. tritici-repentis, without hindering seedling germination and emergence underlaboratory conditions.
Sementes de trigo infectadas com Pyrenophora tritici-repentis, agente causal da mancha-amarela da folha, respondem em parte pelas epidemias causadas por este patógeno. A obtenção rápida de lotes de sementes com alta incidência de P. tritici-repentis é fundamental para estudos de transmissão e controle. Sendo assim, o objetivo deste trabalho foi verificar se alterações no potencial hídrico do meio de cultura e variações na duração da inoculação podem favorecer a infecção de sementes de trigo por P. tritici-repentis, sem comprometer a viabilidade destas sementes. Colônias do patógeno foram cultivadas sobre meio de cultura batata-dextrose-ágar (BDA) básico, no potencial hídrico de -0,36 MPa, e no meio BDA com restrição hídrica, causada pela adição de manitol, nos potenciais hídricos de -0,4, -0,6, -0,8, -1,0 e -1,2 MPa. Foram realizadas análises para determinar o índice de crescimento micelial do fungo e o tempo de exposição das sementes ao meio de cultura para o início do processo germinativo em função dos potenciais hídricos. Posteriormente, sementes de trigo foram colocadas em contato com as colônias de P. tritici-repentis durante 24, 48 e 72 horas nos potenciais hídricos de -0,4, -0,6, -0,8, -1,0 e -1,2 MPa, em esquema fatorial (potenciais hídricos x duração da inoculação) e delineamento inteiramente casualizado. Foram avaliadas as taxas de germinação, de emergência de plântulas em condições de laboratório.
Assuntos
Fungos/crescimento & desenvolvimento , Fungos/enzimologia , Inoculantes Agrícolas/química , Planejamento Hídrico/análise , Sementes/citologia , Sementes/crescimento & desenvolvimentoRESUMO
The enzymes 1,2-diacylglycerol cholinephosphotrans-ferase (CPT) and lysophosphatidylcholine acyltransferase (LPCAT) are important in lipid metabolism in soybean seeds. Thus, understand-ing the genes that encode these enzymes may enable their modification and aid the improvement of soybean oil quality. In soybean, the genes encoding these enzymes have not been completely described; there-fore, this study aimed to identify, characterize, and analyze the in silico expression of these genes in soybean. We identified two gene models encoding CPT and two gene models encoding LPCAT, one of which presented an alternative transcript. The sequences were positioned on the physical map of soybean and the promoter regions were analyzed. Cis-elements responsible for seed-specific expression and responses to biotic and abiotic stresses were identified. Virtual expression analysis of the gene models for CPT and LPCAT indicated that these genes are expressed under different stress conditions, in somatic embryos during differentiation, in immature seeds, root tissues, and calli. Putative ami-no acid sequences revealed the presence of transmembrane domains, and analysis of the cellular localization of these enzymes revealed they are located in the endoplasmic reticulum.