RESUMO
Exposure to abiotic stresses accelerates leaf senescence in most crop plant species, thereby reducing photosynthesis and other assimilatory processes. In some cases, genotypes with delayed leaf senescence (i.e. 'stay-green') show stress resistance, particularly in cases of water deficit, and this has led to the proposal that senescence delay improves crop performance under some abiotic stresses. In this review, we summarize the evidence for increased resistance to abiotic stress, mostly water deficit, in genotypes with delayed senescence, and specifically focus on the physiological mechanisms and agronomic conditions under which the stay-green trait may ameliorate grain yield under stress.
Assuntos
Produtos Agrícolas , Senescência Vegetal , Estresse Fisiológico , Produtos Agrícolas/fisiologia , Produtos Agrícolas/crescimento & desenvolvimento , Produtos Agrícolas/genética , Senescência Vegetal/fisiologia , Folhas de Planta/fisiologiaRESUMO
Resumen Introducción: Poco se conoce del potencial dendrocronológico de las Podocarpáceas en el trópico. Objetivo: Explorar el potencial dendrocronológico de tres especies de podocarpáceas: Retrophyllum rospigliosii, Podocarpus oleifolius y Prumnopitys harmsiana. Métodos: De plantaciones no manejadas localizadas en los Andes colombianos, se muestrearon y analizaron 88 árboles: 30 muestras de R. rospigliosii provenientes de secciones transversales, 30 y 28 muestras de P. oleifolius y P. harmsiana, respectivamente, provenientes de núcleos de madera extraídos con barreno de incrementos. Las muestras se procesaron siguiendo las técnicas dendrocronológicas estándar. Resultados: En general, las características anatómicas de los anillos de crecimiento son similares para las tres especies, con una anatomía simple de traqueidas alineadas radialmente por tratarse de coníferas. Dado que la edad conocida de la plantación coincide con el número de anillos se considera una fuerte evidencia de la frecuencia anual de su formación en R. rospigliosii y P. oleifolius, las cuales presentaron buena sincronización (cofechado) con una inter-correlación promedio de 0.55 (r-Pearson). Para P. harmsiana no fue posible concretar series de ancho de anillos de las muestras recolectadas. Las series estandarizadas de R. rospigliosii y P. oleifolius mostraron una relación con los registros instrumentales de precipitación y temperatura, indicando que estas especies pueden ser promisorias para estudios adicionales. Conclusión: La investigación dendrocronología con especies de Podocarpáceas podría realizarse exitosamente con R. rospigliosii y P. oleifolius, pero no con P. harmsiana.
Abstract Introduction: Little is known about the dendrochronological potential of Podocarpaceaes in the tropics. Objective: To explore the dendrochronological potential of three Podocarpaceae species: Retrophyllum rospigliosii, Podocarpus oleifolius, and Prumnopitys harmsiana. Methods: From a non-managed plantation in the Andean cordillera in Colombia, a total of 88 trees were analyzed: 30 samples of cross-sections of R. rospigliosii, and 30 and 28 samples of P. oleifolius and P. harmsiana, respectively, obtained with an increment borer. Samples were processed according to standard dendrochronological methods. Results: The anatomical characteristics of the growth rings of the three species are similar, with a simple conifer anatomy with radially oriented tracheids. Since the known age of the plantation coincides with the number of tree rings this is strong evidence of annual tree-ring frequency of R. rospigliosii and P. oleifolius which also showed a satisfactory cross-dating with an average inter-correlation of 0.55 (r-Pearson). For P. harmsiana, it was not possible to build a tree-ring series from the collected samples. R. rospigliosii and P. oleifolius standardized ring-width chronologies showed a relationship with the instrumental records of rainfall and temperature, indicating these species may be promising further studies. Conclusions: Dendrochronological research with Podocarpaceae species could be carried out successfully with R. rospigliosii and P. oleifolius but not with P. harmsiana.
Assuntos
Desenvolvimento Vegetal/fisiologia , Traqueófitas/crescimento & desenvolvimento , Senescência Vegetal/fisiologia , Árvores/crescimento & desenvolvimento , Colômbia , Crescimento e DesenvolvimentoRESUMO
Plants are constantly exposed to environmental changes that affect their performance. Metabolic adjustments are crucial to controlling energy homoeostasis and plant survival, particularly during stress. Under carbon starvation, coordinated reprogramming is initiated to adjust metabolic processes, which culminate in premature senescence. Notwithstanding, the regulatory networks that modulate transcriptional control during low energy remain poorly understood. Here, we show that the WRKY45 transcription factor is highly induced during both developmental and dark-induced senescence. The overexpression of Arabidopsis WRKY45 resulted in an early senescence phenotype characterized by a reduction of maximum photochemical efficiency of photosystem II and chlorophyll levels in the later stages of darkness. The detailed metabolic characterization showed significant changes in amino acids coupled with the accumulation of organic acids in WRKY45 overexpression lines during dark-induced senescence. Furthermore, the markedly upregulation of alternative oxidase (AOX1a, AOX1d) and electron transfer flavoprotein/ubiquinone oxidoreductase (ETFQO) genes suggested that WRKY45 is associated with a dysregulation of mitochondrial signalling and the activation of alternative respiration rather than amino acids catabolism regulation. Collectively our results provided evidence that WRKY45 is involved in the plant metabolic reprogramming following carbon starvation and highlight the potential role of WRKY45 in the modulation of mitochondrial signalling pathways.
Assuntos
Proteínas de Arabidopsis , Arabidopsis , Aminoácidos/metabolismo , Arabidopsis/genética , Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Carbono/metabolismo , Escuridão , Regulação da Expressão Gênica de Plantas , Folhas de Planta/metabolismo , Senescência Vegetal , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
NAC transcription factors play critical roles in xylem secondary development and in regulation of stress response in plants. NAC proteins related to secondary cell wall development were recently identified and characterized in Tectona grandis (teak), one of the hardwood trees of highest economic importance in the world. In this work, we characterized the novel TgNAC01 gene, which is involved in signaling pathways that mediate teak response to stress. Abscisic acid (ABA) increases TgNAC01 expression in teak plants. Therefore, this gene may have a role in signaling events that mediate ABA-dependent osmotic stress responsive in this plant species. Stable expression in tobacco plants showed that the TgNAC01 protein is localized in the cell nucleus. Overexpression of TgNAC01 in two out three independent transgenic tobacco lines resulted in increased growth, leaf senescence and salt tolerance compared to wild type (WT) plants. Moreover, the stress tolerance of transgenic plants was affected by levels of TgNAC01 gene expression. Water potential, gas exchange and chlorophyll fluorescence were used to determine salt stress tolerance. The 35S:TgNAC01-6 line under 300 mM NaCl stress responded with a significant increase in photosynthesis rate, stomatal conductance, transpiration and carboxylation efficiency, but lower water potential compared to WT plants. The data indicate that the TgNAC01 transcription factor acts as a transcriptional activator of the ABA-mediated regulation and induces leaf senescence.
Assuntos
Nicotiana , Tolerância ao Sal , Plantas Geneticamente Modificadas/genética , Tolerância ao Sal/genética , Nicotiana/genética , Senescência Vegetal , Proteínas de Plantas/genética , Estresse Salino/genética , Ácido Abscísico/farmacologia , Fatores de Transcrição/genética , Água/metabolismoRESUMO
BACKGROUND: Leaf senescence delay impacts positively in grain yield by maintaining the photosynthetic area during the reproductive stage and during grain filling. Therefore a comprehensive understanding of the gene families associated with leaf senescence is essential. NAC transcription factors (TF) form a large plant-specific gene family involved in regulating development, senescence, and responses to biotic and abiotic stresses. The main goal of this work was to identify sunflower NAC TF (HaNAC) and their association with senescence, studying their orthologous to understand possible functional relationships between genes of different species. RESULTS: To clarify the orthologous relationships, we used an in-depth comparative study of four divergent taxa, in dicots and monocots, with completely sequenced genomes (Arabidopsis thaliana, Vitis vinifera, Musa acuminata and Oryza sativa). These orthologous groups provide a curated resource for large scale protein sequence annotation of NAC TF. From the 151 HaNAC genes detected in the latest version of the sunflower genome, 50 genes were associated with senescence traits. These genes showed significant differential expression in two contrasting lines according to an RNAseq assay. An assessment of overexpressing the Arabidopsis line for HaNAC001 (a gene of the same orthologous group of Arabidopsis thaliana ORE1) revealed that this line displayed a significantly higher number of senescent leaves and a pronounced change in development rate. CONCLUSIONS: This finding suggests HaNAC001 as an interesting candidate to explore the molecular regulation of senescence in sunflower.
Assuntos
Helianthus , Proteínas de Plantas , Senescência Vegetal , Fatores de Transcrição , Arabidopsis/genética , Arabidopsis/metabolismo , Regulação da Expressão Gênica de Plantas , Helianthus/genética , Helianthus/metabolismo , Filogenia , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Senescência Vegetal/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
O teste de envelhecimento acelerado é uma alternativa para avaliação do vigor de sementes, entretanto não há informações suficientes sobre sua eficiência para sementes florestais, como as de Dalbergia nigra (Vell.) Fr. All. (jacarandá-da-bahia). Foi conduzido experimento no Laboratório de Análise de Sementes, da Universidade Federal da Paraíba, com o objetivo de avaliar a qualidade fisiologia de sementes de D. nigra por meio do teste de envelhecimento acelerado. O teste foi conduzido a 41 e 45°C durante 24, 48, 72 e 96 horas, além da testemunha (sementes não envelhecidas). Realizou-se o teste de emergência das plântulas em campo, para verificar a qualidade fisiológica das sementes. As sementes foram distribuídas em camada única sobre tela, em caixas plásticas com 40 mL de água destilada, no interior de câmara BOD. O teor de água e a germinação o vigor das sementes foram determinados antes e após o envelhecimento. O envelhecimento em ambas as temperaturas (41°C e 45°C) a partir de 72 horas, afeta a qualidade fisiológica de sementes de Dalbergia nigra (Vell.) Fr. All., promovendo redução da viabilidade e do vigor.
The accelerated aging test is a possible option for evaluation of seeds vigor, however there is not enough information on your efficiency for forest seeds, as of Dalbergia nigra (Vell.) Fr. All. This study was conducted to investigate procedures to assess seed vigor by the accelerated aging test in seed forest, of Dalbergia nigra. For so much, an experiment was realized at Laboratory of Analysis of Seeds, in Universidad Federal of Paraíba, in Areia - PB, Brazil Northeast. Accelerated aging was performed at 41°C during 24, 48, 72 and 96 hours. Seeds were kept in plastic boxes with 40mL of distilled water in a B.O.D chamber. Seeds were tested for germination and moisture content before and after aging. The aging at both temperatures (41 ° C and 45 ° C) after 72 hours, affect the physiological quality of seeds of Dalbergia nigra (Vell.) Fr All., promoting reduction of viability and vigor.