BIOL - Artigos em revistas internacionais
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- Abiotic stress and induced DNA hypomethylation cause interphase chromatin structural changes in rice rDNA lociPublication . Santos, Ana Paula; Ferreira, Liliana J.; Maroco, João; Oliveira, Maria MargaridaGlobal climate change, i.e. higher and more variable temperatures, and a gain in soil salinity are increasing plant stress with direct consequences on crop yield and quality levels. Rice productivity is strongly affected by abiotic stress conditions. The regulation of chromatin structure in response to environmental stress is poorly understood. We investigated the interphase chromatin organization from rice plants in non-stress versus stress conditions. We have used a cytogenetic approach, based on fluorescence in situ hybridization (FISH) with 45S, 5S rDNA and centromeric probes on rice tissue sections. The abiotic stress conditions included cold, heat and mild salinity and were applied during seed germination. In contrast to cold, saline and heat stresses caused extensive decondensation of 45S rDNA chromatin and also an increase in the distance between the 2 homologous 5S rDNA loci. 5-Azacytidine (5-AC), a DNA hypomethylating drug, greatly increased 45S rDNA chromatin decondensation and interestingly was able to induce polarization of centromeres in rice interphase nuclei. The abiotic stresses tested did not perturb the spatial position of centromeres, typically with circular arrangement around the nucleolus. The results suggest a role for chromatin plasticity in a world of climate changes.
- Accounting for animal density gradients using independent information in distance sampling surveysPublication . Marques, Tiago A.; Buckland, Stephen T.; Bispo, Regina; Howland, BrettDistance sampling is extensively used for estimating animal density or abundance. Conventional methods assume that location of line or point transects is random with respect to the animal population, yet transects are often placed along linear features such as roads, rivers or shorelines that do not randomly sample the study region, resulting in biased estimates of abundance. If it is possible to collect additional data that allow an animal density gradient with respect to the transects to be modelled, we show how to extend the conventional distance sampling likelihood to give asymptotically unbiased estimates of density for the covered area. We illustrate the proposed methods using data for a kangaroo population surveyed by line transects laid along tracks, for which the true density is known from an independent source, and the density gradient with respect to the tracks is estimated from a sample of GPS collared animals. For this example, density of animals increases with distance from the tracks, so that detection probability is overestimated and density underestimated if the non-random location of transects is ignored. When we account for the density gradient, there is no evidence of bias in the abundance estimate. We end with a list of practical recommendations to investigators conducting distance sampling surveys where density gradients could be an issue.
- Analysis of genetic stability at SSR loci during somatic embryogenesis in maritime pine (Pinus pinaster)Publication . Marum, Liliana; Rocheta, Margarida; Maroco, João; Oliveira, Maria Margarida; Miguel, Célia M.Somatic embryogenesis (SE) is a propagation tool of particular interest for accelerating the deployment of new high-performance planting stock in multivarietal forestry. However, genetic conformity in in vitro propagated plants should be assessed as early as possible, especially in long-living trees such as conifers. The main objective of this work was to study such conformity based on genetic stability at simple sequence repeat (SSR) loci during somatic embryogenesis in maritime pine (Pinus pinaster Ait.). Embryogenic cell lines (ECLs) subjected to tissue proliferation during 6, 14 or 22 months, as well as emblings regenerated from several ECLs, were analyzed. Genetic variation at seven SSR loci was detected in ECLs under proliferation conditions for all time points, and in 5 out of 52 emblings recovered from somatic embryos. Three of these five emblings showed an abnormal phenotype consisting mainly of plagiotropism and loss of apical dominance. Despite the variation found in somatic embryogenesis-derived plant material, no correlation was established between genetic stability at the analyzed loci and abnormal embling phenotype, present in 64% of the emblings. The use of microsatellites in this work was efficient for monitoring mutation events during the somatic embryogenesis in P. pinaster. These molecular markers should be useful in the implementation of new breeding and deployment strategies for improved trees using SE.
- Are tidal lagoons ecologically relevant to larval recruitment of small pelagic fish : an approach using nutritional condition and growth ratePublication . Chícharo, M.A.; Amaral, A.; Faria, A.; Morais, P.; Mendes, C.; Piló, D.; Ben-Hamadou, R.; Chícharo, L.There are numerous studies dealing with larvae of Small Pelagic Fish (SPF), but only a few have actually addressed advanced larval phases. Temperate coastal lagoons are particularly understudied, due to the absence of standard method to capture advanced larval fish in these near shore shallow habitats. Accordingly, this study aims to describe abundances, nutritional condition and in situ growth of postflexion (SPF) from the Ria Formosa, a tidal coastal lagoon in southern Portugal. The nutritional condition and in situ growth were determined through cohort analysis and standardized RNA:DNA ratio (sRD), complemented with feeding incidence (gut content) and fatty acids (FAs, trophic biomarkers) of postflexion larvae sampled sequentially with light traps, from spring 2005 to summer 2006. Simultaneously, environmental parameters such as water temperature, salinity, dissolved oxygen and chlorophyll a were measured. Post-larvae of SPF were captured through the year in important numbers. The dominant species were Sardina pilchardus (50.7%), Engraulis encrasicolus and Atherina presbyter (11.4%). These results are distinct from those based on adult/juvenile surveys or early planktonic phases in the Ria Formosa where clupeiformes were occasionally reported. Sardines were captured mainly in winter, spring and early summer and anchovies mainly during summer and autumn. Sand smelt, a resident species, was present throughout the year. In the early summer, the three species were present and during this period some diet overlapping occurred, the feeding incidence of the clupeiformes was very low, but atherinids always exhibited full guts reflecting the different gut morphology or indicating different lifecycle strategies. The bulk of the diet was mollusks, crustaceans and appendicularians, for sand smelts, sardines and anchovies, respectively. The results of FA analyses showed some contribution of phytoplankton to SPF in the area. All SPF exhibited higher condition (sRD) and growth rates in summer, which are explained by the adequate temperature and higher planktonic productivity. This is especially relevant because the successful development of postflexion larvae in these nursery areas largely determines the successful recruitment to adult fish populations.
- Bridging sd1 molecular knowledge with recent breeding strategies for the improvement of traditional rice varieties - a japonica case-studyPublication . Negrão, Sónia; Palaniappan, Jayamani; Maroco, João; Lourenço, Tiago; Mackill, David; Oliveira, Maria MargaridaThe rice semidwarfing gene, sd1, also known as the “green revolution gene”, has been studied intensively due to its contribution to the increase of crop production. Although sd1 breeding was extensively applied since the 1960s, the recent advances in the molecular basis of this gene allowed designing a more precise breeding strategy - marker assisted backcrossing (MAB) - to track sd1 introgression in two traditional rice varieties. For selection of sd1 plants we first confirmed the efficiency of specific markers based on Os200 x 2 gene sequence. Background selection was also performed with the help of microsatellites markers (SSR) and a total of 7 breeding lines were recovered containing a higher percentage of recurrent parent genome (RPG). Analysis of Covariance (ANCOVA) using mean progenitor plant height as covariate was performed to compare several agronomic and quality-related parameters in two different environments. The results suggest that plant height differs significantly between the two environments F(1, 220) = 155.336; p < 0.001. From the total variability of plant height we could conclude that 73% is due to the genotype, while 10.4% depends on the environment. In addition, the percentage of RPG seems negatively correlated with plant height (p < 0.005). MAB and background selection thus revealed as useful tools to assist breeding for semidwarfism in traditional rice varieties.
- Control of stomatal aperture and carbon uptake by deficit irrigation in two grapevine cultivarsPublication . Souza, Cláudia R. de; Maroco, João; Santos, Tiago P.; Rodrigues, M. Lucília; Lopes, Carlos Manuel Antunes; Pereira, João Santos; Chaves, Maria Manuelaodels for the Mediterranean region. In recent years, deficit irrigation, including partial root drying (PRD), has been proposed as an irrigation technique to improve water use efficiency and standardize grapevine yield and quality. The objective of this study was to evaluate the impact of deficit irrigation on photosynthetic responses of field grown grapevines of cv. Moscatel and Castela˜o. The treatments were: full irrigation (FI), corresponding to 100% ETc; non-irrigated, but rain fed (NI) and partial root zone drying (PRD) and deficit irrigation (DI), both corresponding to an irrigation of 50% ETc. While in the DI treatment water was applied to both sides of the root system, in the PRD treatment, water was supplied to only one side of the root system, alternating sides periodically. In both cultivars, PRD and DI vines showed intermediate pre-dawn leaf water potential (ψpd) values (around -0.4 MPa) while FI vines, showed ψpd around -0.2 MPa during the growing season. NI showed the lowest cpd, reaching -0.6 MPa in Moscatel and -0.8 MPa in Castelão, at the end of growing season. Water status of PRD vines remained closer to FI than DI, especially at midday. Photosynthetic rates and fluorescence parameters of the deficit irrigation treatments (PRD and DI) did not show significant differences from FI vines, for most of the season. In Moscatel, although PRD generally showed gs, relative stomatal limitation (RSL) and intrinsic water use efficiency (A/gs) values closer to NI than DI, most of the differences between PRD and DI were not statistically significant. Our results showed a stability of the photosynthetic machinery in grapevines under low-to-moderate water availabilities, as demonstrated by the maintenance of the activity of three Calvin Cycle enzymes and of the Vcmax values. However, a decline in Jmax was observed in NI vines, that can be a result either of a decrease in ATP production or, alternatively, of decreased mesophyll conductance to CO2 diffusion. In general terms, stomatal limitation of photosynthesis is likely to be dominant in non-irrigated plants. Deficit irrigation had no negative impact on CO2 assimilation, despite less water application than in full-irrigation. Differences among varieties may be related to differences in sensitivity of stomata, shoot growth and/or the interaction between rootstock and cultivar to soil water availability.
- A deepening understanding of animal culture suggests lessons for conservationPublication . Brakes, Philippa; Carroll, Emma L; Dall, Sasha R X; Keith, Sally Anne; McGregor, Peter; Mesnick, Sarah L.; Noad, Michael; Rendell, Luke Edward; Robbins, Martha M.; Rutz, Christian; Thornton, Alex; Whiten, Andrew; Whiting, Martin J.; Aplin, Lucy M.; Bearhop, Stuart; Ciucci, Paolo; Fishlock, Vicki; Ford, John K. B.; Sciara Di, Giuseppe Notarbartolo; Simmonds, Mark P.; Spina, Fernando; Wade, Paul R.; Whitehead, Hal; Williams, James; Garland, Ellen C.A key goal of conservation is to protect biodiversity by supporting the long-term persistence of viable, natural populations of wild species. Conservation practice has long been guided by genetic, ecological and demographic indicators of risk. Emerging evidence of animal culture across diverse taxa and its role as a driver of evolutionary diversification, population structure and demographic processes may be essential for augmenting these conventional conservation approaches and decision-making. Animal culture was the focus of a ground-breaking resolution under the Convention on the Conservation of Migratory Species of Wild Animals (CMS), an international treaty operating under the UN Environment Programme. Here, we synthesize existing evidence to demonstrate how social learning and animal culture interact with processes important to conservation management. Specifically, we explore how social learning might influence population viability and be an important resource in response to anthropogenic change, and provide examples of how it can result in phenotypically distinct units with different, socially learnt behavioural strategies. While identifying culture and social learning can be challenging, indirect identification and parsimonious inferences may be informative. Finally, we identify relevant methodologies and provide a framework for viewing behavioural data through a cultural lens which might provide new insights for conservation management.
- Deficit irrigation in grapevine improves water-use efficiency while controlling vigour and production qualityPublication . Chaves, Maria Manuela; Santos, Tiago P.; Souza, Cláudia R. de; Ortuño, M. F.; Rodrigues, M. Lucília; Lopes, Carlos Manuel Antunes; Maroco, João; Pereira, João SantosGrapevine irrigation is becoming an important practice to guarantee wine quality or even plant survival in regions affected by seasonal drought. Nevertheless, irrigation has to be controlled to optimise source to sink balance and avoid excessive vigour. The results we present here in two grapevine varieties (Moscatel and Castela ˜o) during 3 years, indicate thatwe can decrease the amount ofwater applied by 50%(as in deficit irrigation, DI, and in partial root drying, PRD) in relation to full crop’s evapotranspiration (ETc) [full irrigated (FI) vines] with no negative effects on production and even get some gains of quality (in the case of PRD).We report that in non-irrigated and in several cases in PRD vines exhibit higher concentrations of berry skin anthocyanins and total phenols than those presented by DI and FI vines.We showed that these effects on quality weremediated by a reduction in vigour, leading to an increase on light interception in the cluster zone. Because plant water status during most of the dates along the season was not significantly different between PRD and DI, and when different, PRD even exhibited a higher leaf water potential than DI vines, we conclude that growth inhibition in PRD was not a result of a hydraulic control. The gain in crop water use in DI and PRD was accompanied by an increase of the δ13 C values in the berries in DI and PRD as compared to FI, suggesting that we can use this methodology to assess the integrated water-use efficiency over the growing season.
- Demographic history has shaped the strongly differentiated corkwing wrasse populations in Northern EuropePublication . Mattingsdal, Morten; Jorde, Per Erik; Knutsen, Halvor; Jentoft, Sissel; Stenseth, Nils Christian; Sodeland, Marte; Robalo, Joana I; Hansen, Michael M.; André, Carl; Gonzalez, Enrique BlancoUnderstanding the biological processes involved in genetic differentiation and divergence between populations within species is a pivotal aim in evolutionary biology. One particular phenomenon that requires clarification is the maintenance of genetic barriers despite the high potential for gene flow in the marine environment. Such patterns have been attributed to limited dispersal or local adaptation, and to a lesser extent to the demographic history of the species. The corkwing wrasse (Symphodus melops) is an example of a marine fish species where regions of particular strong divergence are observed. One such genetic break occurred at a surprisingly small spatial scale (FST ~0.1), over a short coastline (<60 km) in the North Sea-Skagerrak transition area in southwestern Norway. Here, we investigate the observed divergence and purported reproductive isolation using genome resequencing. Our results suggest that historical events during the post-glacial recolonization route can explain the present population structure of the corkwing wrasse in the northeast Atlantic. While the divergence across the break is strong, we detected ongoing gene flow between populations over the break suggesting recent contact or negative selection against hybrids. Moreover, we found few outlier loci and no clear genomic regions potentially being under selection. We concluded that neutral processes and random genetic drift e.g., due to founder events during colonization have shaped the population structure in this species in Northern Europe. Our findings underline the need to take into account the demographic process in studies of divergence processes.
- Drought stress response in Jatropha curcas: Growth and physiologyPublication . Sapeta, Helena; Costa, J. Miguel; Lourenço, Tiago; Maroco, João; Van der Linde, Piet; Oliveira, Maria MargaridaTolerance to drought remains poorly described for Jatropha curcas accessions from different geographical and climatic origins. To address this issue we studied the response of two J. curcas accessions, one from Indonesia (wet tropical climate) and the other from Cape Verde islands (semi-arid climate). Potted seedlings (with 71 days) of both accessions were subjected to continuous well watered conditions (control) or to a drought stress period followed by re-watering. To mimic natural conditions in which drought stress develops gradually, stress was imposed progressively by reducing irrigation (10% reduction every 2 days, on a weight base), for a period of 28 days, until a field capacity of 15% (maximum stress) was achieved, followed by one week under well-watered conditions. We measured soil and plant water status, growth and biomass partitioning, leaf morphology, leaf gas exchange and chlorophyll a fluorescence. Both accessions maintained high leaf relative water content (70–80%) even at maximum stress. Net photosynthesis (An) was not affected by mild to moderate stress but it abruptly dropped at severe stress. This was due to reduced stomatal conductance, which showed earlier decline than An. Plant growth (stem elongation, leaf emergence and total leaf area) was reduced, minimizing water loss, but no significant differences were found between accessions. Drought stress did not reduce chlorophyll contents but led to reduced chlorophyll a/b. Both accessions showed fast recovery of both stomatal and photochemical parameters suggesting a good tolerance to water stress. Both J. curcas accessions showed a-dehydrationavoidant behaviour, presenting a typical water saving strategy due to strict stomatal regulation, regardless of their provenance.