Biologia Vegetal

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Combinatorial regulation modules on GmSBP2 promoter: a distal cis-regulatory domain confines the SBP2 promoter activity to the vascular tissue in vegetative organs
(Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression, 2006-03-10) Waclawovsky, Alessandro J.; Freitas, Rejane L.; Rocha, Carolina S.; Contim, Luis Antônio S.; Fontes, Elizabeth P.B.
The Glycine max sucrose binding protein (GmSBP2) promoter directs phloem-specific expression of reporter genes in transgenic tobacco. Here, we identified cis-regulatory domains (CRD) that contribute with positive and negative regulation for the tissue-specific pattern of the GmSPB2 promoter. Negative regulatory elements in the distal CRD-A (−2000 to −700) sequences suppressed expression from the GmSBP2 promoter in tissues other than seed tissues and vascular tissues of vegetative organs. Deletion of this region relieved repression resulting in a constitutive promoter highly active in all tissues analyzed. Further deletions from the strong constitutive −700GmSBP2 promoter delimited several intercalating enhancer-like and repressing domains that function in a context-dependent manner. Histochemical examination revealed that the CRD-C (−445 to −367) harbors both negative and positive elements. This region abolished promoter expression in roots and in all tissues of stems except for the inner phloem. In contrast, it restores root meristem expression when fused to the −132pSBP2-GUS construct, which contains root meristem expression-repressing determinants mapped to the 44-bp CRD-G (−136 to −92). Thus, the GmSBP2 promoter is functionally organized into a proximal region with the combinatorial modular configuration of plant promoters and a distal domain, which restricts gene expression to the vascular tissues in vegetative organs.
Comprehensive metabolic reprograming in freshwater Nitzschia palea strains undergoing nitrogen starvation is likely associated with its ecological origin
(Algal Research, 2016-09) Machado, Mariana; Bromke, Mariusz; Domingues Júnior, Adilson Pereira; Vaz, Marcelo Gomes Marçal Vieira; Rosa, Rinamara Martins; Vinson, Christina C.; Sabir, Jamal S.; Rocha, Diego Ismael; Martins, Marcio Arêdes; Araújo, Wagner L.; Willmitzer, Lothar; Szymanski, Jedrzej; Nunes-Nesi, Adriano
Nitrogen deficiency can increase the lipid content in certain microalgae species, including diatoms. However, the molecular and metabolic basis of such changes remains rather unclear. We analyzed strains of freshwater Nitzschia palea collected from a eutrophic pond and from an artificial rock. The habitats, differing in light and nutrient availability, lead to two metabolically distinct strains, BR006 and BR022. Differential accumulation of primary compounds, membrane lipid composition and fatty acid saturation were observed. Metabolic and biophysical analysis demonstrated differential sensitivity to N regimes: depleted, replete and saturated. Whereas N depletion leads to typical stress-related responses in both strains, including reduction of protein and photosynthesis, the response observed in BR006 is far more severe. Our results demonstrated that these strains developed distinct metabolic responses to N conditions. BR022 is able to maintain cellular homeostasis and slows down growth according to N availability. In contrast, BR006 maximizes growth rate even under N limitation, by triggering stress response, relocating carbon pool to lipid compounds and quickly reaching growth arrest after N exhaustion. We identified a relationship between habitat characteristics and metabolic responses, providing a metabolic perspective on ecological plasticity of N. palea, which helps it to survive a wide range of habitats.
The Crambe abyssinica plastome: Brassicaceae phylogenomic analysis, evolution of RNA editing sites, hotspot and microsatellite characterization of the tribe Brassiceae
(Gene, 2018-09-10) Lopes, Amanda de Santana; Pacheco, Túlio Gomes; Vieira, Leila do Nascimento; Guerra, Miguel Pedro; Nodari, Rubens Onofre; Souza, Emanuel Maltempi de; Pedrosa, Fábio de Oliveira; Rogalski, Marcelo
Crambe abyssinica is an important oilseed crop that accumulates high levels of erucic acid, which is being recognized as a potential oil platform for several industrial purposes. It belongs to the family Brassicaceae, assigned within the tribe Brassiceae. Both family and tribe have been the subject of several phylogenetic studies, but the relationship between some lineages and genera remains unclear. Here, we report the complete sequencing and characterization of the C. abyssinica plastome. Plastome structure, gene order, and gene content of C. abyssinica are similar to other species of the family Brassicaceae. The only exception is the rps16 gene, which is absent in many genera within the family Brassicaceae, but seems to be functional in the tribe Brassiceae, including C. abyssinica. However, the analysis of gene divergence shows that the rps16 is the most divergent gene in C. abyssinica and within the tribe Brassiceae. In addition, species of the tribe Brassiceae also show similar SSR loci distribution, with some regions containing a high number of SSRs, which are located mainly at the single copy regions. Six hotspots of nucleotide divergence among Brassiceae species were located in the single copy regions by sliding window analysis. Brassicaceae phylogenomic analysis, based on the complete plastomes of 72 taxa, resulted in a well-supported and well-resolved tree. The genus Crambe is positioned within the Brassiceae clade together with the genera Brassica, Raphanus, Sinapis, Cakile, Orychophragmus and Sinalliaria. Moreover, we report several losses and gains of RNA editing sites that occurred in plastomes of Brassiceae species during evolution.
Edible coatings containing chitosan and moderate modified atmospheres maintain quality and enhance phytochemicals of carrot sticks
(Postharvest Biology and Technology, 2009-03) Simões, Adriano D. N.; Tudela, Juan A.; Allende, A.; Puschmann, Rolf; Gil, Maria I.
Carrot sticks are increasingly in demand as ready-to-eat products, with a major quality problem in the development of white discoloration. Modified atmosphere packaging (MAP) and edible coating have been proposed as postharvest treatments to maintain quality and prolong shelf-life. The combined application of an edible coating containing 5 mL L^−1 of chitosan under two different MAP conditions (10 kPa O2 + 10 kPa CO2 in Pack A and 2 kPa O2 + 15–25 kPa CO2 in Pack B) over 12 d at 4 °C was studied. Respiration rate, microbial and sensory qualities as well as the contents of vitamin C, carotenoids and phenolics of coated and uncoated carrot sticks were evaluated. The use of the edible coating containing chitosan preserved the overall visual quality and reduced surface whiteness during storage. Microbial populations were very low and not influenced by coating or MAP. Edible coating increased respiration rates of carrot sticks, although this was only noticeable in the package with the less permeable film (Pack B). Vitamin C and carotenoids decreased during storage particularly in coated carrot sticks. In contrast, the content of total phenolics markedly increased in coated carrot sticks stored under moderate O2 and CO2 levels, while it was controlled under low O2 and high CO2 levels. The combined application of edible coating containing chitosan and moderate O2 and CO2 levels maintained quality and enhanced phenolic content in carrot sticks.
Effects of simulated acid rain on the foliar micromorphology and anatomy of tree tropical species
(Environmental and Experimental Botany, 2006-12) Sant’Anna-Santos, Bruno Francisco; Silva, Luzimar Campos da; Azevedo, Aristéa Alves; Araújo, João Marcos de; Alves, Ericka Figueiredo; Silva, Eldo Antônio Monteiro da; Aguiar, Rosane
In order to correlate sintomatology with anatomical alterations caused by acid rain in leaves of tropical species, seedlings and saplings of Spondias dulcis Forst. F., Mimosa artemisiana Heringer and Paula and Gallesia integrifolia (Spreng.) Harms were exposed to simulated low-pH acid rain (pH 3.0). Control plants were submitted only to rain with distilled water (pH 6.0). The plants were exposed daily to the acid rain for 20 min for 10 consecutive days. Necrotic spots on the leaf blade occurred and most of the injuries onset on the epidermis in all species studied. S. dulcis displayed epicuticular wax erosion and rupture of epidermis. The abaxial surface of M. artemisiana was colonized by a mass of fungi hyphae and stomatal outer ledge rupture occurred. Some epidermal cells of G. integrifolia showed appearance similar to plasmolysis. The plants accumulated phenolic compounds in necrotic areas. Afterwards, leaves presented injuries in the mesophyll and collapsed completely. Cells surrounding the injured areas accumulated starch grains in S. dulcis. M. artemisiana showed more drastic symptom intensity in response to acidic rain. S. dulcis displayed visual symptoms similar to G. integrifolia, however, anatomical alterations were more severe.
Effects of simulated deposition of acid mist and iron ore particulate matter on photosynthesis and the generation of oxidative stress in Schinus terebinthifolius Radii and Sophora tomentosa L.
(Science of The Total Environment, 2008-06-20) Kuki, Kacilda Naomi; Oliva, Marco Antônio; Pereira, Eduardo Gusmão; Costa, Alan Carlos; Cambraia, José
Particulate matter is a natural occurrence in the environment, but some industries, such as the iron ore sector, can raise the total amount of particles in the atmosphere. This industry is primarily a source of iron and sulfur dioxide particulates. The effects of the pollutants from the iron ore industries on representatives of restinga vegetation in a Brazilian coastal ecosystem were investigated using physiological and biochemical measures. Two species, Schinus terebinthifolius and Sophora tomentosa, were exposed to simulated deposition of acid mist and iron ore particulate matter in acrylic chambers in a greenhouse. Parameters such as gas exchange, fluorescence emission, chlorophyll content, total iron content, antioxidant enzyme activity and malondialdehyde content were assessed in order to evaluate the responses of the two species. Neither treatment was capable of inducing oxidative stress in S. terebinthifolius. Nevertheless, the deposition of iron ore particulates on this species increased chlorophyll content, the maximum quantum efficiency of photosystem II and the electron transport rate, while iron content was unaltered. On the other hand, S. tomentosa showed a greater sensitivity to the treatments. Plants of S. tomentosa that were exposed to acid mist had a decrease in photosynthesis, while the deposition of iron particulate matter led to an increase in iron content and membrane permeability of the leaves. The activities of antioxidant enzymes, such as catalases and superoxide dismutase, were enhanced by both treatments. The results suggested that the two restinga species use different strategies to overcome the stressful conditions created by the deposition of particulate matter, either solid or wet. It seems that while S. terebinthifolius avoided stress, S. tomentosa used antioxidant enzyme systems to partially neutralize oxidative stress. The findings also point to the potential use of S. tomentosa as a biomarker species under field conditions.
The functional divergence of biomass partitioning, carbon gain and water use in Coffea canephora in response to the water supply: Implications for breeding aimed at improving drought tolerance
(Environmental and Experimental, 2012-10-04) Silva, Paulo E. M.; Cavatte, Paulo C.; Morais, Leandro E.; Medina, Eduardo F.; DaMatta, Fábio M.
Robusta coffee (Coffea canephora) is widely cultivated in regions where water availability is the major environmental constraint affecting crop production. The functional divergence associated with biomass partitioning, carbon gain and water use in response to water supply was examined in 10 one-year-old clones of robusta coffee with varying degrees of droughttolerance. The plants were grown outdoors in 24 L pots and either irrigated or subjected to a four-month water deficit. Under conditions of ample irrigation, clones with superior water use ability (i.e., a higher water potential,transpiration rate, apparent hydraulic conductance and biomass partitioning into roots and a lower wood density) displayed enhanced carbon gains. In contrast, under drought conditions, clones that postponed dehydration via more conservative water use rates showed lower relative decreases in stomatal conductance, photosynthetic rates and biomass accumulation. Isotopic signatures (13C) might be useful for identifying clones with improved performance under drought conditions. Our results suggest that combining useful morphological and physiological traits facilitates the successful assessment of coffee clonal performance in response to drought at the seedling stage. This strategy may be valuable when exploring a large number of genotypes in coffee-breeding programs because it reduces the time and resource costs that would otherwise be wasted on potentially undesirable genotypes.
Guard cell-specific down-regulation of the sucrose transporter SUT1 leads to improved water use efficiency and reveals the interplay between carbohydrate metabolism and K+ accumulation in the regulation of stomatal opening
(Environmental and Experimental Botany, 2017-03) Antunes, Werner Camargos; Daloso, Danilo de Menezes; Pinheiro, Daniela Pereira; Williams, Thomas Christopher Rhys; Loureiro, Marcelo Ehlers
Sucrose is a key metabolite in guard cell (GC) regulation and has been proposed to form a key metabolic connection between mesophyll cells and GCs. However, the importance of sucrose transport across the GC plasma membrane in stomatal movements remains to be determined. Here, we characterized transgenic tobacco plants expressing an antisense gene construct for the SUCROSE TRANSPORTER 1 (SUT1) driven by the GC specific promoter KST1. GCs of transgenic plants contained less sucrose, more starch and had increases in K+ content. Lower GC sucrose content was associated with lower stomatal conductance that, in turn, led to a lower transpiration rate and higher carbon isotope composition ratio compared to wild type plants. Although the transgenic plants showed reduced growth under optimal water supply condition, they showed improved growth compared to wild type plants under osmotic stress and demonstrated lower water consumption that was correlated with higher relative water content under water-deficit conditions. This demonstrates the desiccation postponement phenotype of these plants together with an improved tolerance to water deficit. Taken together, our results indicate that SUT1 has an important role in stomatal movements and suggest that genetic manipulation of GC sucrose transport could be used to obtain plants with greater water use efficiency.
Hiya: A new genus segregated from Hypolepis in the fern family Dennstaedtiaceae, based on phylogenetic evidence and character evolution
(Molecular Phylogenetics and Evolution, 2018-05-01) Schwartsburd, Pedro B.; Shang, Hui; Sundue, Michael; Wei, Ran; Wei, Xue-Ping; Liu, Li; Yan, Yue-Hong; Zhang, Xian-Chun; Luo, Jun-Jie
The relationship of Hypolepis brooksiae, H. nigrescens, and H. scabristipes to the remainder of Hypolepis (Dennstaedtiaceae) has been questioned by previous authors based on their unique combination of morphological characters and different base chromosome number. Using four chloroplast genes including rbcL, atpA, rpL6, and rps4-trnS intergenic spacer (IGS) from 32 samples, representing 24 species of Dennstaedtiaceae, we recovered a clade comprising H. brooksiae and H. nigrescens, distinct from the remaining species of Hypolepis. This clade is resolved as sister to the clade comprising Blotiella, Paesia and Histiopteris. We reconstructed ancestral states of 16 morphological characters and found that this clade is distinguished by indeterminate, scandent leaves exhibiting rhythmic growth, provided with recurved black-tipped prickles, and stipule-like pinnules that protect the emerging crosier and pinnae departures, rachis-costa architecture where the adaxial sulcus is confluent with the next lower order, and a base chromosome number of x = 29. In light of this molecular and morphological evidence, we describe a new genus, Hiya, and provide nomenclatural combinations to accommodate the three known species segregated from Hypolepis: Hiya brooksiae, Hiya nigrescens, and Hiya scabristipes.
Insecticidal effect of nanoencapsulated essential oils from Zanthoxylum rhoifolium (Rutaceae) in Bemisia tabaci populations Author links open overlay panel
(Industrial Crops and Products, 2015-08) Christofoli, Marcela; Costa, Eliangela Cristina Candida; Bicalho, Keylla U.; Domingues, Vanessa de Cássia; Peixoto, Márcio Fernandes; Alves, Cassia Cristina Fernandes; Araújo, Wagner L.; Cazal, Cristiane de Melo
The purpose of this study was to develop and characterize biodegradable nanospheres containing essential oils from Zanthoxylum rhoifolium leaves and evaluate its insecticidal effect in Bemisia tabaci populations. The essential oil from Z. rhoifolium leaves exhibited an average yield of 0.03% and presented β-elemene (31.26%), D-germacrene (18.16%), β-caryophyllene (12.09%), δ-elemene (7.63%), β-cedrene (6.69%), bicyclogermacrene (4.57%) and E-caryophyllene (3.63%) as main components. The PCL nanospheres containing this essential oil exhibited encapsulation efficiency higher than 96%, pH close to 5, particle diameter smaller than 500 nm and zeta potential values of approximately −20 mV. The in vitro release profile was characteristic of biphasic release, i.e., a fast initial release, followed by slow release for 12 h or more. The biological assay results were also significant and as such both the in natura and nanoencapsulated essential oils resulted in reductions as high as 95% in the number of eggs and nymphs compared with our control. Collectively these results suggest that both in natura and nanoencapsulated essential oils from Z. rhoifolium leaves can potentially be used in B. tabaci control in association with integrated pest management practices.
Loss of type-IV glandular trichomes is a heterochronic trait in tomato and can be reverted by promoting juvenility
(Plant Science, 2017-03-14) Zsögön, Agustin; Vendemiatti, Eloisa; Silva, Geraldo Felipe Ferreira e; Jesus, Frederico Almeida de; Cutri, Lucas; Figueiredo, Cassia Regina Fernandes; Tanaka, Francisco André Ossamu; Nogueira, Fábio Tebaldi Silveira; Peres, Lázaro Eustáquio Pereira
Glandular trichomes are structures with widespread distribution and deep ecological significance. In the Solanum genus, type-IV glandular trichomes provide resistance to insect pests. The occurrence of these structures is, however, poorly described and controversial in cultivated tomato (Solanum lycopersicum). Optical and scanning electron microscopy were used to screen a series of well-known commercial tomato cultivars, revealing the presence of type-IV trichomes on embryonic (cotyledons) and juvenile leaves. A tomato line overexpressing the microRNA miR156, known to promote heterochronic development, and mutants affecting KNOX and CLAVATA3 genes possessed type-IV trichomes in adult leaves. A re-analysis of the Woolly (Wo) mutant, previously described as enhancing glandular trichome density, showed that this effect only occurs at the juvenile phase of vegetative development. Our results suggest the existence of at least two levels of regulation of multicellular trichome formation in tomato: one enhancing different types of trichomes, such as that controlled by the WOOLLY gene, and another dependent on developmental stage, which is fundamental for type-IV trichome formation. Their combined manipulation could represent an avenue for biotechnological engineering of trichome development in plants.
Methyl jasmonate and salicylic acid are able to modify cell wall but only salicylic acid alters biomass digestibility in the model grass Brachypodium distachyon
(Plant Science, 2017-07-08) Napoleão, Thiago Alves; Soares, Giuliana; Vital, Camilo Elber; Bastos, Carla; Castro, Robson; Loureiro, Marcelo Ehlers; Giordano, Andrea
In addition to playing a key role in the response to environmental changes, cell walls are also considered as a valuable feedstock for cellulosic ethanol. Here we explored the effects of the stress-response hormones, salicylic acid and methyl jasmonate, on cell wall biosynthesis and biomass digestibility in Brachypodium distachyon, a species recently considered as a suitable model for biomass conversion. We found that in response to salicylic acid or methyl jasmonate treatment, plant growth was reduced coupled with significant changes in cell wall composition. Cellulose content increased in response to methyl jasmonate whereas a reduction in lignin content was found after salicylic acid application. Moreover, hemicellulose composition was altered and increases in caffeic acid, ferulic acid and p-coumaric acid content were detected in response to both treatments. The hormonal profile and the expression pattern of genes involved in cell wall biosynthesis were also modified. Biomass digestibility was reduced in leaf tissue after salicylic acid treatment and was negatively correlated with ferulic acid and p-coumaric acid content. The results obtained here aid in our understanding of cell wall dynamics in response to stress and will enable the development of new strategies to improve cell wall digestibility in bioenergy feedstock.
Morphological responses of different eucalypt clones submitted to glyphosate drift
(Environmental and Experimental Botany, 2007-01) Santos, Leonardo David Tuffi; Meira, Renata Maria Strozi Alves; Ferreira, Francisco Affonso; Sant’Anna-Santos, Bruno Francisco; Ferreira, Lino Roberto
This work aimed to evaluate the effects of simulated glyphosate drift on leaf growth and micromorphology of Eucalyptus spp. clones, using subdoses. A factorial scheme consisting of three clones, Eucalyptus urophylla, E. grandis and the hybrid E. urophylla × E. grandis (E. urograndis) and five sub-rates (0; 43.2; 86.4; 172.8 and 345.6 g e.a. ha^−1 of glyphosate) were used in a randomized block design, with four repetitions. The herbicide was applied on the plants so as not to reach the superior third, 23 days after seedling planting. At 7 and 15 days after application (DAA), the leaves collected from the first basal branch of the plants were processed according to the conventional methodology used for micromorphological studies. The effects of glyphosate drift were proportional to the rates tested, with E. urophylla being more tolerant to the herbicide than E. grandis and E. urograndis. Glyphosate symptoms were the same for the different clones tested, being characterized by wilting, chlorosis and leaf curling, and, at higher rates, by necrosis, foliar senescence and death of the eucalypt plants. Plants submitted to 172.8 and 345.6 g ha^−1 of glyphosate had severe injuries in the aerial part, affecting their development, resulting in reduced height, stem diameter and dry mass at 50 DAA. The micromorphological damages occurred prior to the appearance of visible symptoms, with erosion of the epicuticular waxes and fungal hypha infestation in plants exposed to glyphosate drift being observed in the three clones. No marked difference in leaf micromorphology was observed that could explain the differential tolerance among the three clones studied. The results show that further studies on wax and cuticle constitution of Eucalyptus spp. are needed for the elucidation of the mechanisms of differential tolerance of eucalypt species and clones to glyphosate.
Phenotypic markers in early selection for tolerance to dieback in Eucalyptus
(Industrial Crops and Products, 2017-11-15) Corrêa, Thais Roseli; Picoli, Edgard Augusto de Toledo; Souza, Genaína Aparecida de; Condé, Samyra Alves; Silva, Natália Machado; Lopes-Mattos, Karina Lucas Barbosa; Resende, Marcos Deon Vilela de; Zauza, Edival Angelo Valverde; Oda, Shinitiro
Eucalyptus dieback is a physiological disorder characterized by lesions on the apex of the branches and the death of the shoot apex. Some clones are considered tolerant to this disorder, although, up to now, there are no reports on the use of phenotypic markers for selecting tolerant material. The use of phenotypic markers may contribute to an efficient selection, where the estimation of genetic parameters of the candidate markers are essential to knowledge of the population structure, the genetic potential and effectiveness of markers as selection criteria. In this study, we estimated the genetic parameters of morphological and nutritional markers in 13 commercial eucalyptus clones aiming early selection of tolerant genotypes to eucalyptus dieback. Estimates of the genetic parameters of all characteristics were obtained by the mixed model methodology, REML (Restricted Maximum Likelihood)/BLUP (Best Linear Unbiased Prediction) procedure. Water deficit, one of the factors that promote this disorder, was simulated in eucalyptus cuttings conducted in a greenhouse. Simulated water stress was carried out for 12 weeks by applying polyethylene glycol at different concentrations and by limiting water applied to seedlings. In order to select the most promising markers, 34 morphological and nutritional variables were evaluated for early selection and discrimination of genotypes tolerant to eucalyptus dieback and water deficit. Among the 34 evaluated characteristics, plant height, stem diameter, height increment, leaf area, N, K and B, exhibited significant heritability and high accuracy (greater than 70%). Promising phenotypic markers were identified for early selection of genotypes tolerant to water deficit and eucalyptus dieback. Tolerant clones were pooled and correctly discriminated from the susceptible ones under stressful conditions by the use of seven phenotypic markers in REML/BLUP analysis, selection index ranking and graphic dispersion analysis.
Phenotypic plasticity in response to light in the coffee tree
(Environmental and Experimental Botany, 2009-12) DaMatta, Fábio M.; Matos, Fábio S.; Wolfgramm, Ricardo; Gonçalves, Fábio V.; Cavatte, Paulo C.; Ventrella, Marília C.
Phenotypic plasticity to light availability was examined at the leaf level in field-grown coffee trees (Coffea arabica). This species has been traditionally considered as shade-demanding, although it performs well without shade and even out-yields shaded coffee. Specifically, we focused our attention on the morpho-anatomical plasticity, the balance between light capture and excess light energy dissipation, as well as on physiological traits associated with carbon gain. A wide natural light gradient, i.e., a diurnal intercepted photon irradiance differing by a factor of 25 between the deepest shade leaves and the more exposed leaves in the canopy, was explored. Responses of most traits to light were non-linear, revealing the classic leaf sun vs. leaf shade dichotomy (e.g., compared with sun leaves, shade leaves had a lower stomatal density, a thinner palisade mesophyll, a higher specific leaf area, an improved light capture, a lower respiration rate, a lower light compensating point and a limited capacity for photoprotection). The light-saturated rates of net photosynthesis were higher in sunlit than in shade leaves, although sun leaves were not efficient enough to use the extra light supply. However, sun leaves showed well-developed photoprotection mechanisms in comparison to shade leaves, which proved sufficient for avoiding photoinhibition. Specifically, a higher non-photochemical quenching coefficient was found in parallel to increases in: (i) zeaxanthin pools, (ii) de-epoxidation state of the xanthophyll cycle, and (iii) activities of some antioxidant enzymes. Intracanopy plasticity depended on the suite of traits considered, and was high for some physiological traits associated with photoprotection and maintenance of a positive carbon balance under low light, but low for most morpho-anatomical features. Our data largely explain the successful cultivation of the coffee tree in both exposed and shade environments, although with a poor resource-use efficiency in high light.
Photosynthesis and oxidative stress in the restinga plant species Eugenia uniflora L. exposed to simulated acid rain and iron ore dust deposition: Potential use in environmental risk assessment
(Science of The Total Environment, 2009-03-24) Neves, Natália Rust; Oliva, Marco Antonio; Centeno, Danilo da Cruz; Costa, Alan Carlos; Ribas, Rogério Ferreira; Pereira, Eduardo Gusmão
The Brazilian sandy coastal plain named restinga is frequently subjected to particulate and gaseous emissions from iron ore factories. These gases may come into contact with atmospheric moisture and produce acid rain. The effects of the acid rain on vegetation, combined with iron excess in the soil, can lead to the disappearance of sensitive species and decrease restinga biodiversity. The effects of iron ore dust deposition and simulated acid rain on photosynthesis and on antioxidant enzymes were investigated in Eugenia uniflora, a representative shrub species of the restinga. This study aimed to determine the possible utility of this species in environmental risk assessment. After the application of iron ore dust as iron solid particulate matter (SPMFe) and simulated acid rain (pH 3.1), the 18-month old plants displayed brown spots and necrosis, typical symptoms of iron toxicity and injuries caused by acid rain, respectively. The acidity of the rain intensified leaf iron accumulation, which reached phytotoxic levels, mainly in plants exposed to iron ore dust. These plants showed the lowest values for net photosynthesis, stomatal conductance, transpiration, chlorophyll a content and electron transport rate through photosystem II (PSII). Catalase and superoxide dismutase activities were decreased by simulated acid rain. Peroxidase activity and membrane injury increased following exposure to acid rain and simultaneous SPMFe application. Eugenia uniflora exhibited impaired photosynthetic and antioxidative metabolism in response to combined iron and acid rain stresses. This species could become a valuable tool in environmental risk assessment in restinga areas near iron ore pelletizing factories. Non-invasive evaluations of visual injuries, photosynthesis and chlorophyll a fluorescence, as well as invasive biochemical analysis could be used as markers.
Postharvest salicylic acid treatment reduces storage rots in water-stressed but not unstressed sugarbeet roots
(Elsevier Postharvest Biology and Technology, 2013-11) Fugate, Karen Klotz; Ferrareze, Jocleita Peruzzo; Bolton, Melvin D.; Deckard, Edward L.; Campbell, Larry G.; Finger, Fernando L.
Exogenous application of salicylic acid (SA) reduces storage rots in a number of postharvest crops. SA's ability to protect sugarbeet (Beta vulgaris L.) taproots from common storage rot pathogens, however, is unknown. To determine the potential of SA to reduce storage losses caused by three common causal organisms of sugarbeet storage rot, freshly harvested roots were treated with 0.01, 0.1, 1.0 or 10 mM SA, inoculated with Botrytis cinerea, Penicillium claviforme, or Phoma betae, and evaluated for the severity of rot symptoms after incubation at 20 °C and 90% relative humidity. Roots were obtained from plants that received sufficient water or were water-stressed prior to harvest. Roots from water-stressed plants were included since water-stress increases sugarbeet root susceptibility to storage rot and SA mitigates drought effects in other plant species. SA at concentrations of 0.01–10 mM had no effect on the severity of storage rot caused by B. cinerea, P. claviforme, or P. betae in roots from plants that received sufficient water prior to harvest. However, SA at these same concentrations reduced the severity of rot symptoms for all three pathogens in roots from plants that were water stressed before harvest. For water-stressed roots, all concentrations of SA produced statistically equivalent reductions in the weight of rotted tissue for each pathogen, and on average, SA reduced rot severity due to B. cinerea, P. claviforme, and P. betae by 54, 45, and 58%, respectively. SA reduced rot from all three pathogens by reducing lesion size, but did not affect the incidence of infection. The ability of SA to reduce rot severity in water-stressed roots, but not in roots that received sufficient water before harvest suggests that SA alleviated the negative impact of water stress but did not directly protect sugarbeet roots against storage rots.
The role of silicon in metabolic acclimation of rice plants challenged with arsenic
(Environmentaland Experimental Botany, 2015-11-14) Sanglard, Lílian M.V.P.; Detmann, Kelly C.; Martins, Samuel C.V.; Teixeira, Rodrigo A.; Pereira, Lucas F.; Sanglard, Matheus L.; Fernie, Alisdair R.; Araújo, Wagner L.; DaMatta, Fábio M.
Silicon (Si) plays key roles in alleviating various abiotic stresses, including arsenic (As) toxicity, via physiological mechanisms that remain poorly understood. Here, we combined photosynthetic measurements with analyses of central metabolism and gene expression to explore the consequences of As-related alterations on primary metabolism and examined whether these consequences could be affected by the application of Si to rice (Oryza sativa L.) plants challenged with As but supplemented with Si. The negative effects of As on photosynthesis and carbohydrate status were largely reversed by Si. However, no major metabolic reprogramming was observed, as denoted by minor, if any, significant changes in (i) the activities of a range of enzymes associated with C metabolism; (ii) the levels of a wide range of organic acids and amino acids; and (iii) the pools of NAD(P)H/NAD(P)+ and the redox states of ascorbate and glutathione. Arsenic toxicity was apparently unrelated to oxidative stress. We suggested that the search for As-tolerant plants under real field conditions should not focus solely on oxidative stress, and hence the focus on photosynthesis might be of higher significance. In conclusion, we identified Si nutrition as a central player that restricts photosynthetic impairment in As-treated plants, in addition to limiting As uptake via modulation of the expression of genes with prime importance in As uptake and translocation.
Structural adaptation and anatomical convergence in stems and roots of five plant species from a “Restinga” sand coastal plain
(Flora, 2018-06) Kuster, Vinícius Coelho; Silva, Luzimar Campos da; Meira, Renata Maria Strozi Alves; Azevedo, Aristéa Alves
Coastal areas present limiting environmental conditions, such as high soil salinity, intense winds, elevated temperature and coastal flooding, which may be related to adaptive anatomical characters. This study aims to evaluate the anatomy of the stems and roots of Restinga plants (eudicots: Blutaparon portulacoides, Canavalia rosea, Ipomoea pes-caprae and Scaevola plumieri; monocot: Remirea maritima) and their relationship to parameters of the microenvironment. These five species were selected because they are dominant and present great occurrence in Restinga vegetation nearest to the sea. Stems and roots of five species (n = 5) were fixed and submitted to standard techniques for analyzing under light microscope. Wind velocity, air temperature, air relative humidity and evaporation level were evaluated close to individuals and above them. The nutritional conditions from rhizosphere were also estimated. The winds were weak close to individuals, while the temperature was higher than compared to measurements above individuals. Minor differences of the soil were noted between areas close and far from the plants. Seven anatomical characters may be related to adaptability to the stressful conditions, as stem succulence, root aerenchyma, root starch reserves and epidermal cell of the stems with thick outer periclinal walls, however there was little convergence between species. Aerenchyma and water reserve tissue were the most frequent anatomical traits. In contrast, elevated cortex lignification in roots was the lowest occurrence trait, being a specific feature of the monocot.
Transcriptional memory contributes to drought tolerance in coffee (Coffea canephora) plants
(Environmental and Experimental Botany, 2017-12-10) DaMatta, Fábio Murilo; Nobres, Priscilla; Ferreira, Daniela Cristina Rodrigues; Menezes-Silva, Paulo Eduardo; Ribeiro-Alves, Marcelo; Correa, Régis Lopes; Alves-Ferreira, Márcio; Guedes, Fernanda Alves de Freitas
Water deprivation is an important limiting factor in the productivity of crops like coffee. In addition to transcription factors (TFs) and small non-coding RNAs, transcriptional memory seems to act in gene expression modulation during plant drought response. Here, a RNA-Seq approach was used to investigate the drought responses of Coffea canephora clones 109 and 120, which are respectively sensitive and tolerant to drought. Illumina sequencing allowed us to identify differentially expressed genes (DEG) in the tolerant (826) and sensitive (135) clones and their enriched categories. Our results indicate that the sensitive clone may trigger an oxidative stress response, possibly leading to programmed cell death, when exposed to multiple drought episodes. The acclimation of tolerant plants, on the other hand, seems to involve antioxidant secondary metabolism and the ABA response. Most importantly, 49 memory genes were identified in the tolerant clone. They were mainly linked to the ABA pathway, protein folding and biotic stress. Small RNA profiling also identified regulatory microRNAs in coffee leaves, including hundreds of putative novel ones. Our findings strongly suggest that transcriptional memory modulates the expression of drought-responsive genes and contributes to drought tolerance in C. canephora.