Biologia Vegetal

URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/11836

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Alternative carbon sources for isoprene Emission
(Trends in Plant Science, 2018-12-01) Araújo, Wagner L.; Souza, Vinícius Fernandes de; Niinemets, Ülo; Rasulov, Bahtijor; Vickers, Claudia E.; Duvoisin Júnior, Sergio; Gonçalves, José Francisco de Carvalho
Isoprene and other plastidial isoprenoids are produced primarily from recently assimilated photosynthates via the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. However, when environmental conditions limit photosynthesis, a fraction of carbon for MEP pathway can come from extrachloroplastic sources. The flow of extrachloroplastic carbon depends on the species and on leaf developmental and environmental conditions. The exchange of common phosphorylated intermediates between the MEP pathway and other metabolic pathways can occur via plastidic phosphate translocators. C1 and C2 carbon intermediates can contribute to chloroplastic metabolism, including photosynthesis and isoprenoid synthesis. Integration of these metabolic processes provide an example of metabolic flexibility, and results in the synthesis of primary metabolites for plant growth and secondary metabolites for plant defense, allowing effective use of environmental resources under multiple stresses.
Changes in non-structural carbohydrates in developing fruit of Myrciaria jaboticaba
(Scientia Horticulturae, 1996-10) Barros, Raimundo S.; Finger, Fernando L.; Magalhães, Marcelo M.
Reducing sugars represented the main non-structural carbohydrate of fruit of Myrciaria jaboticaba owing to the high content found in pulp, which also accumulated most of the non-reducing sugars. The contribution of the skin to the amount of total sugar in the berry was negligible. Starch was relatively low in the pulp but more abundant in the seed.
Data-mining bioinformatics: connecting adenylate transport and metabolic responses to stress
(Trends in Plant Science, 2018-11) Fonseca-Pereira, Paula da; Neri-Silva, Roberto; Cavalcanti, João Henrique F.; Brito, Danielle S.; Weber, Andreas P. M.; Araújo, Wagner L.; Nunes-Nesi, Adriano
Adenine nucleotides are essential in countless processes within the cellular metabolism. In plants, ATP is mainly produced in chloroplasts and mitochondria through photophosphorylation and oxidative phosphorylation, respectively. Thus, efficient adenylate transport systems are required for intracellular energy partitioning between the cell organelles. Adenylate carriers present in different subcellular compartments have been previously identified and biochemically characterized in plants. Here, by using data-mining bioinformatics tools, we propose how, and to what extent, these carriers integrate energy metabolism within a plant cell under different environmental conditions. We demonstrate that the expression pattern of the corresponding genes is variable under different environmental conditions, suggesting that specific adenylate carriers have distinct and nonredundant functions in plants.
Differential root and shoot responses in the metabolism of tomato plants exhibiting reduced levels of gibberellin
(Environmental and Experimental Botany, 2019-01) Martins, Auxiliadora O.; Omena-Garcia, Rebeca P.; Oliveira, Franciele S.; Silva, Welder A.; Hajirezaei, Mohammad-Reza; Vallarino, José G.; Ribeiro, Dimas Mendes; Fernie, Alisdair R.; Nunes-Nesi, Adriano; Araújo, Wagner L.
The ability to adapt to the environment is crucial for plant survival and thus a refined communication system capable of integrating endogenous and exogenous signals and further relaying this information to different parts of the plant is a key component of such adaptability. Given that they grow in highly distinct environments it is arguably unsurprising that roots and shoots display different responses to a given environmental condition. Accordingly, a higher sensitivity of roots to gibberellins (GAs) allows rapid adjustments in growth and development possibly triggering (a) stress tolerance mechanism(s). Here we investigated the differential metabolic responses between root and shoot following reductions of the endogenous GA content using tomato (Solanum lycopersicum L.) plants deficient in GA biosynthesis (gib3, moderately deficient, gib2, intermediate deficiency and gib1, extremely deficient in GAs). GA depletion impedes shoot growth to a greater extent than root growth in all mutants. Moreover, the greater the reduction in GA content the greater the extent of a disturbance at the metabolic level. Low leaf carbohydrate contents were observed in plants displaying higher root growth, suggesting an enhanced flow of photoassimilate to support root growth. Large increases in amino acids contents of either roots or shoot were observed. The increased amino acid content was coupled to reduced levels of TCA cycle intermediates suggesting that these changes are directly linked to early reactions of nitrogen assimilation. The combined data are discussed in terms of our current understanding of the interaction between GA and primary metabolism and their crosstalk in environmental responses.
How to distinguish cavities from ducts in Casearia Jacq. (Salicaceae): Anatomical characterization and distribution
(Flora, 2018-03) Fernandes, Valéria Ferreira; Thadeo, Marcela; Dalvi, Valdnéa Casagrande; Marquete, Ronaldo; Silva, Julianna Xavier de Brito; Pereira, Luana de Jesus; Meira, Renata Maria Strozi Alves
Pellucid punctuations and lines in the leaf blade are common in Casearia, but for some of its species these structures are mentioned as inconspicuous, not visible or obscure. Cavities and ducts have been anatomically described and correlated with pellucid punctuations and lines, respectively, in only six species from the genus; however, the distinction between these types of secretory structures remains unclear. Therefore, we aimed to anatomically describe the pellucid punctuations and lines in leaves of 47 species of Casearia. Leaf blade samples were obtained from herbarium and field collected material and processed according to standard methods for light microscopy analysis. Cavities and ducts were absent in only four of the 47 species (C. commersoniana, C. javitensis and C. spruceana of section Piparea, and C. eicheleriana of section Casearia). In the remaining species, cavities corresponded to pellucid punctuations, while ducts corresponded with lines. The majority of species have both structures randomly distributed throughout the leaf blade, however, in C. bahiensis, these structures are concentrated along the leaf margin, while in C. aquifolia and C. crassinervis they were predominant along the midrib. Our data show that anatomical analyses are essential for distinguishing between cavities and ducts. We also demonstrate that the distribution of cavities and ducts provides useful information for the taxonomy of Casearia at both the species and section levels.
Insights into ABA-mediated regulation of guard cell primary metabolism revealed by systems biology approaches
(Progress in Biophysics and Molecular Biology, 2018) Medeiros, David B.; Araújo, Wagner L.; Yoshida, Takuya; Anjos, Letícia dos; Fernie, Alisdair R.; Daloso, Danilo M.
Despite the fact that guard cell abscisic acid (ABA) signalling pathway is well documented, our understanding concerning how and to which extent ABA regulates guard cell metabolism remains fragmentary. Here we have adopted different systems approaches to investigate how ABA modulates guard cell central metabolism by providing genes that are possibly ABA-regulated. By using previous published Arabidopsis guard cell transcript profiling data, we carried out an extensive co-expression network analysis using ABA-related genes and those related to the metabolism and transport of sugars, starch and organic acids. Next, we investigated the presence of ABA responsive elements (ABRE) in the promoter of genes that are highly expressed in guard cells, responsive to ABA and co-expressed with ABA-related genes. Together, these analyses indicated that 44 genes are likely regulated by ABA and 8 of them are highly expressed in guard cells in both the presence and absence of ABA, including genes of the tricarboxylic acid cycle and those related to sucrose and hexose transport and metabolism. It seems likely that ABA may modulate both sucrose transport through guard cell plasma membrane and sucrose metabolism within guard cells. In this context, genes associated with sucrose synthase, sucrose phosphate synthase, trehalose-6-phosphate, invertase, UDP-glucose epimerase/pyrophosphorylase and different sugar transporters contain ABRE in their promoter and are thus possibly ABA regulated. Although validation experiments are required, our study highlights the importance of systems biology approaches to drive new hypothesis and to unravel genes and pathways that are regulated by ABA in guard cells.
Limitations to photosynthesis in Coffea canephoraas a result of nitrogen and water availability
(Journal of Plant Physiology, 2002) DaMatta, Fábio M.; Loos, Rodolfo A.; Silva, Emerson A.; Loureiro, Marcelo E.
Plants of C. canephora grown in pots under low nitrogen (LN) or high nitrogen (HN) applications were submitted to either cyclic water stress or daily irrigation. Water deficit led to marked decreases in net carbon assimilation rate (A) and, to a lesser extent, in stomatal conductance (gs), regardless of the N treatments. In well-watered plants, A appreciably increased in HN plants relative to LN plants without significant changes in gs. As a whole, changes in internal CO2 concentration predominantly reflected changes in A rather than in gs. Under irrigated conditions, A, but not gs, correlated with leaf N concentration in a curvilinear way. Photosynthetic nitrogen-use efficiency was considerably low, and decreased with increasing leaf N concentration. Limited N, but not water, slightly decreased the maximum photochemical efficiency of photosystem II (PSII). Under continuous irrigation, LN plants had a smaller quantum yield of electron transport (ϕPSII) through slight decreases of photochemical quenching (qp) and capture efficiency of excitation energy by open PSII reaction centres, and increases in Stern-Volmer non-photochemical quenching. Under water-stressed conditions, changes in PSII photochemistry were apparent only in HN plants, with a 25 % decrease in ϕPSII, due mainly to variations in qp. Biochemical constraints, rather than stomatal or photochemical limitations, provoked the decreases in A under limited supply of either N or water.
Metallic nanoparticles influence the structure and function of the photosynthetic apparatus in plants
(Plant Physiology and Biochemistry, 2018-09) Nunes-Nesi, Adriano; Tighe-Neira, Ricardo; Carmora, Erico; Recio, Gonzalo; Reyes-Diaz, Marjorie; Alberdi, Miren; Rengel, Zed; Inostroza-Blancheteau, Claudio
The applications of nanoparticles continue to expand into areas as diverse as medicine, bioremediation, cosmetics, pharmacology and various industries, including agri-food production. The widespread use of nanoparticles has generated concerns given the impact these nanoparticles – mostly metal-based such as CuO, Ag, Au, CeO2, TiO2, ZnO, Co, and Pt - could be having on plants. Some of the most studied variables are plant growth, development, production of biomass, and ultimately oxidative stress and photosynthesis. A systematic appraisal of information about the impact of nanoparticles on these processes is needed to enhance our understanding of the effects of metallic nanoparticles and oxides on the structure and function on the plant photosynthetic apparatus. Most nanoparticles studied, especially CuO and Ag, had a detrimental impact on the structure and function of the photosynthetic apparatus. Nanoparticles led to a decrease in concentration of photosynthetic pigments, especially chlorophyll, and disruption of grana and other malformations in chloroplasts. Regarding the functions of the photosynthetic apparatus, nanoparticles were associated with a decrease in the photosynthetic efficiency of photosystem II and decreased net photosynthesis. However, CeO2 and TiO2 nanoparticles may have a positive effect on photosynthetic efficiency, mainly due to an increase in electron flow between the photosystems II and I in the Hill reaction, as well as an increase in Rubisco activity in the Calvin and Benson cycle. Nevertheless, the underlying mechanisms are poorly understood. The future mechanistic work needs to be aimed at characterizing the enhancing effect of nanoparticles on the active generation of ATP and NADPH, carbon fixation and its incorporation into primary molecules such as photo-assimilates.
Molecular identification of a further branched-chain aminotransferase 7 (BCAT7) in tomato plant
(Journal of Plant Physiology, 2012-03-15) Araújo, Wagner Luiz; Kochevenko, Andrej S.; Klee, Harry J.; Fernie, Alisdair R.
Although the branched-chain amino acids (BCAAs) are essential components of the mammalian diet, our current understanding of their metabolism in plants is still limited. It is however well known that the branched-chain amino acid transaminases (BCATs) play a crucial role in both the synthesis and degradation of the BCAAs leucine, isoleucine and valine. We previously characterized the BCAT gene family in tomato, revealing it to be highly diverse in subcellular localization, substrate preference, and expression. Here we performed further characterization of this family and provide evidence for the presence of another member, BCAT7. On mapping the chromosomal location of this enzyme, it was possible to define the exact chromosome map position of the gene. Although in Arabidopsis thaliana the AtBCAT7 has been considered a pseudo-gene, quantitative evaluation of the expression levels of this gene revealed that the expression profile of the BCAT7 in different tissues of tomato (Solanum lycopersicum cv. M82) plants is highly variable with the highest expression found in developed flowers. By using a C-terminal E-GFP gene fusion we demonstrate that the BCAT7 is extraplastidial and in combination with the kinetic characterization of BCAT7 our results suggest that it most likely operates in BCAA degradation in vivo and support our hypothesis of another functional member of BCAT family. The combined data presented are discussed within the context of BCAA metabolism and its functions in higher plants.
Morphogenic gradients of adventitious bud and shoot regeneration in epicotyl explants of Citrus
(Scientia Horticulturae, 2014-03-19) Costa, M. G. C; Alves, V. S.; Lani, E. R. G.; Mosquim, P. R.; Carvalho, C. R.; Otoni, W. C.
The in vitro responses of epicotyl explants from ‘Cravo’ rangpur lime (Citrus limonia Osb.), ‘Foster’ grapefruit (C. paradisi Macf.), and ‘Pera’ sweet orange (C. sinensis (L.) Osb.) were characterized for the first time. Further analysis was performed in ‘Cravo’ rangpur lime and ‘Foster’ grapefruit aiming to verify the in vitro morphogenesis of five distinct regions of the epicotyl under different treatments. It was observed the same general pattern of morphogenic gradient along the epicotyl axis in both citrus cultivars, with greater organogenic response as the distance of the explants from the cotyledonary node increased. This morphogenic gradient was influenced by factors related to plant material, composition of the culture medium, and conditions of incubation. The regions of the epicotyl farthest from cotyledons could be used as a source of explants in experiments of genetic transformation of the genotypes evaluated aiming to improve the efficiency of production of transgenic Citrus plants.
The reproductive biology of Cybistax antisyphilitica (Bignoniaceae), a characteristic tree of the South American savannah-like “Cerrado” vegetation
(Flora - Morphology, Distribution, Functional Ecology of Plants, 2011-10) Bittencourt Jr., Nelson Sabino; Pereira Jr., Eduardo João; São-Thiago, Paula de Souza; Semir, João
Bignoniaceous woody species are very important ecological components of neotropical forests, but the reproductive biology of many species, such as Cybistax antisyphilitica, remains virtually unknown. Most species of Bignoniaceae are characteristically self-sterile, despite typically exhibiting normal pollen tube growth throughout the style, combined with slow rates of ovule penetration, fertilisation and endosperm initiation in selfed pistils. Uniform abortion occurs within a few days of anthesis, indicating the occurrence of late-acting self-incompatibility (LSI). However, breeding system studies have been performed in fewer than 7% of species, and other types of breeding systems (e.g., self-compatibility and apomixis) have been reported in this family. In the present study, the reproductive biology of C. antisyphilitica was investigated by field observation of flower visitors and floral events. Moreover, reproductive biology of this species was examined through experimental pollinations, analyses of pollen tube growth and ovule penetration using fluorescence microscopy, verification of pistil longevity, and a histological analysis of unpollinated vs. self-pollinated pistils. Finally, morphological aspects, quantities and germination were investigated in seeds that resulted from different pollination treatments. Natural pollination was effected by large- and medium-sized bees, and their visiting behaviour favours a high proportion of geitonogamy and no pollen limitation. Self-pollinated flowers produced no fruits, and all of the characteristic post-pollination events cited above were verified, witnessing the occurrence of LSI with post-zygotic rejection of selfed pistils in C. antisyphilitica. Although some indications of extended pistil longevity were found in selfed pistils, this feature seemed to be affected by unidentified environmental factors. The seeds were always monoembryonic and with high viability. A larger variation in the number of viable seeds was found in fruits derived from natural pollination. A low fruit set was observed after both natural and cross-pollination, and most crossed fruits underwent abortion at several points during the juvenile phase, even when protected against herbivory. The formation of surplus flowers/juvenile fruits and the apparently wasteful selfing mechanism control implied in LSI are discussed in the context of the perennial life style of tropical woody plant species.
Salt stress inhibits germination of Stylosanthes humilis seeds through abscisic acid accumulation and associated changes in ethylene production
(Plant Physiology and Biochemistry, 2018-09) Silva, Nilo C. Q.; Souza, Genaina A. de; Pimenta, Thaline M.; Brito, Fred A. L.; Picoli, Edgard A. T.; Zsögön, Agustín; Ribeiro, Dimas M.
In Stylosanthes humilis, salt stress tolerance is associated with ethylene production by the seeds, however, how salt stress controls seed germination and ethylene production is poorly understood. Here, we studied the hormonal and metabolic changes triggered by salt stress on germination of S. humilis seeds. Salt stress led to decreased seed germination and ethylene production, concomitantly with higher abscisic acid (ABA) production by seeds. Treatment with NaCl and ABA promoted distinct changes in energy metabolism, allowing seeds to adapt to salt stress conditions. Treatment with the ABA biosynthesis inhibitor fluridone or ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) reversed the effects of salt stress on seed germination and ethylene production. Moreover, ethylene concentration was decreased by increasing the pH of the salt solution. High pH, however, did not influence concentration of ABA in seeds under salt stress. We conclude that biosynthesis of ABA and ethylene in response to salt stress constitutes a point of convergence that provides flexibility to regulate energy metabolism and embryo growth potential of S. humilis seeds within a given pH condition.
Sensibility of Spondias purpurea L. (Anacardiaceae) exposed to fluoride-simulated fog
(Ecological Indicators, 2018-07) Anjos, Talles Bruno Oliveira dos; Louback, Eliza; Azevedo, Aristéa Alves; Silva, Luzimar Campos da
Fluoride is the atmospheric pollutant with the highest phytotoxicity arising from aluminum smelting fertilizers, glass and, ceramic industry. The most affected plant organ is the leaf, in which the fluoride penetrates through two main ways: absorption by epidermis cuticle or absorption by stomata. Species susceptible to fluoride are potential tools in bioindicator studies because they provide a means for detecting the presence of the pollutant in the environment at a low cost. The aim of this study is to evaluate the sensibility of Spondias purpurea L. (Anacardiaceae) to fluoride through the simulated fog. Simulation was performed by applying 500 ml of solution containing 15 mg L−1 of potassium fluoride per plant for 20 min daily and for 10 consecutive days. The data of leaflet abscission, visual damage, and climate conditions were recorded daily. At the end of the experiment, data from the cell death analysis, electrolyte leakage determination, and accumulation of the fluoride in the dried matter were collected. Moreover, samples for phenolic compound accumulation, anatomical, and micromorphological analyses were collected. After 24 h, the appearance of visible damage was observed in the leaves with fluoride treatment. This damage consisted, mostly, of necrosis, chlorosis, and leaf apical shriveling. The necroses manifested in gray and brown discoloration. Leaf abscission was intense in the young leaves. Microscopic damage consisted of protoplast retraction, phenolic compound accumulation, collapse, hyperplasia, and cell rupture. Turgidity loss, epicuticular wax erosion, and damage of stomata and trichomes beyond the presence of fungal hyphae were noted in the epidermis. Evans Blue detected dead cell groups in the transition region between the necrosis and the apparent healthy area. Fluoride affected the selective permeability of the membrane, which was observed in this study according to the high rate of electrolyte leakage. Plants exposed to fluoride accumulated 14.48 times more fluoride in their leaves than plants in the control group. It follows that S. purpurea is susceptible to fluoride and responds quickly to the presence of this pollutant. Marginal and apical necrosis, presence of phenolic compounds, fluoride accumulation, anatomical alterations, and leaflet abscission in the young leaves are biomarkers of fluoride effects in this species. Therefore, S. purpurea is potentially useful in biomonitoring programs.
Sexual ornaments reveal the strength of melanization immune response and longevity of male paper wasps
(Journal of Insect Physiology, 2018-08) Souza, André Rodrigues de; Simões, Talitta Guimarães; Rantala, Markus J.; Santos, Eduardo Fernando; Lino-Netto, José; Nascimento, Fábio Santos do
It has been recently suggested that female mate choice, based on sexually selected ornaments, is an important component of social wasps’ reproductive biology. The correlates of male ornaments that could be of a female’s interest, however, remain to be investigated. Males of the Neotropical paper wasp Polistes simillimus have sexually dimorphic melanin-based black spots on their faces. In this species, male spots work like sexual ornaments, as it has been experimentally demonstrated that females prefer sexual partners with a higher proportion of black pigment on their faces. We have shown that, under laboratory conditions, male sexual ornamentation positively predicts the strength of the melanization immune response and longevity. Therefore, in P. simillimus, melanin-based facial patterns (ornaments) seem to be honest indicators of male quality.
Unraveling interfaces between energy metabolism and cell cycle in plants
(Trends in Plant Science, 2018-08) Nunes-Nesi, Adriano; Siqueira, João Antonio; Hardoim, Pablo; Ferreira, Paulo C. G.; Hemerly, Adriana S.
Oscillation in energy levels is widely variable in dividing and differentiated cells. To synchronize cell proliferation and energy fluctuations, cell cycle-related proteins have been implicated in the regulation of mitochondrial energy-generating pathways in yeasts and animals. Plants have chloroplasts and mitochondria, coordinating the cell energy flow. Recent findings suggest an integrated regulation of these organelles and the nuclear cell cycle. Furthermore, reports indicate a set of interactions between the cell cycle and energy metabolism, coordinating the turnover of proteins in plants. Here, we discuss how cell cycle-related proteins directly interact with energy metabolism-related proteins to modulate energy homeostasis and cell cycle progression. We provide interfaces between cell cycle and energy metabolism-related proteins that could be explored to maximize plant yield.
Virus-induced gene silencing of pea CHLI and CHLD affects tetrapyrrole biosynthesis, chloroplast development and the primary metabolic network
(Plant Physiology and Biochemistry, 2013-04) Araújo, Wagner Luiz; Luo, Tao; Luo, Sha; Schlicke, Hagen; Rothbart, Maxi; Yu, Jing; Fan, Tingting; Fernie, Alisdair R.; Grimm, Bernhard; Luo, Meizhong
The first committed and highly regulated step of chlorophyll biosynthesis is the insertion of Mg2+ into protoporphyrin IX, which is catalyzed by Mg chelatase that consists of CHLH, CHLD and CHLI subunits. In this study, CHLI and CHLD genes were suppressed by virus-induced gene silencing (VIGS-CHLI and VIGS-CHLD) in pea (Pisum sativum), respectively. VIGS-CHLI and VIGS-CHLD plants both showed yellow leaf phenotypes with the reduced Mg chelatase activity and the inactivated synthesis of 5-aminolevulinic acid. The lower chlorophyll accumulation correlated with undeveloped thylakoid membranes, altered chloroplast nucleoid structure, malformed antenna complexes and compromised photosynthesis capacity in the yellow leaf tissues of the VIGS-CHLI and VIGS-CHLD plants. Non-enzymatic antioxidant contents and the activities of antioxidant enzymes were altered in response to enhanced accumulation of reactive oxygen species (ROS) in the chlorophyll deficient leaves of VIGS-CHLI and VIGS-CHLD plants. Furthermore, the results of metabolite profiling indicate a tight correlation between primary metabolic pathways and Mg chelatase activity. We also found that CHLD induces a feedback-regulated change of the transcription of photosynthesis-associated nuclear genes. CHLD and CHLI silencing resulted in a rapid reduction of photosynthetic proteins. Taken together, Mg chelatase is not only a key regulator of tetrapyrrole biosynthesis but its activity also correlates with ROS homeostasis, primary interorganellar metabolism and retrograde signaling in plant cells.