Effects of short-term arsenic exposure in Arabidopsis thaliana : tolerance versus toxicity responses

The metalloid arsenic (As) is highly phytotoxic, in part due to the similarity of the arsenates to phosphates, but also due to its ability to induce reactive oxygen species (ROS) formation, and in the form of arsenite directly interact with certain enzymes. Here we aimed to determine the effects of a short period of As exposure on Arabidopsis thaliana. Particular focus was given to shoot responses, which have received less attention in previous studies. A. thaliana (ecotype Col-0) plants (28-d-old) were cultivated hydroponically in the presence of 0, 27, 108, and 216 M arsenic in the form of sodium arsenate for five days. Translocation of As from root to shoot increased with increasing As concentration in the medium and caused a reduction in growth. Photosynthesis was severely affected due to stomatal closure, increased ROS accumulation, and alterations in expression of genes involved in oxidative stress responses and As detoxification. Primary metabolism was also perturbed, suggesting both the direct inhibition of certain enzymes as well as active defensive responses. Overall the effects of As toxicity depended greatly on the degree of translocation from root to shoot and involved both direct effects on biological processes and secondary effects caused by the accumulation of ROS

HD‑Zip I subfamily gene expression in soybean subjected to drought

O objetivo deste trabalho foi identificar genes candidatos da subfamília de fatores transcricionais HD‑Zip I que contribuem para a tolerância à seca em soja. Foram avaliados trifólios de soja de cultivar tolerante (Embrapa  48) e suscetível à seca (BR  16), sob três níveis de deficit hídrico: ausência, moderado (‑1,5 MPa) e severo (‑3,0 MPa). Pela análise dos promotores, foi identificada a presença de possíveis elementos cis-regulatórios relacionados à resposta à seca, nos três genes avaliados (GmHB6, GmHB13 e GmHB21). No entanto, não houve padrão de distribuição específico associado à maior tolerância do genótipo à seca. Com a análise comparativa, foram identificados seis elementos cis‑regulatórios potencialmente envolvidos na indução da expressão gênica sob seca. O gene GmHB13 foi exclusivamente induzido pela seca no genótipo tolerante, e o gene GmHB6 apresentou redução da expressão somente no genótipo suscetível. Já o gene GmHB21, apresentou aumento da expressão em ambos os genótipos. O gene GmHB13 é um importante elemento na regulação do mecanismo de tolerância à seca em soja, na cultivar tolerante Embrapa 48.The objective of this work was to identify candidate genes of the HD‑Zip I transcription factors subfamily that contribute to drought tolerance in soybean. Trifoliate soybean leaves of drought tolerant (Embrapa 48) and susceptible (BR 16) cultivars were evaluated under three levels of drought: absence, moderate (-1.5 MPa), and severe (-3.0 MPa). Promoter analysis indicated the presence of putative cis-regulatory elements related to water stress in the three genes evaluated (GmHB6, GmHB13, and GmHB21). However, there was no specific pattern of distribution associated with the higher drought tolerance of the genotype. By comparative analysis, six cis-regulatory elements potentially involved in the induction of gene expression under drought were identified. Gene GmHB13 was exclusively induced by drought in the tolerant cultivar, and GmHB6 had its expression reduced only in the susceptible cultivar. Gene GmHB21 showed increased expression in both genotypes. Gene GmHB13 is an important element in the regulation of the drought tolerance mechanism in soybean, in the tolerant cultivar Embrapa 48

Physiological response of Conilon coffee clone sensitive to drought grafted onto tolerant rootstock

O objetivo deste trabalho foi determinar alterações fisiológicas e de tolerância à seca em clones de café Conilon (Coffea canephora) contrastantes quanto à sensibilidade ao deficit hídrico. Foram avaliadas as enxertias recíprocas entre os clones 109A, sensível ao deficit hídrico, e 120, tolerante – 120/109A, 120/120, 109A/120, 109A/109A –, além de seus respectivos pés-francos. As plantas foram cultivadas em vasos de 12 L em casa de vegetação. Após seis meses, metade das plantas foi submetida ao deficit hídrico por meio da suspensão da irrigação, até que as folhas atingissem o potencial hídrico de antemanhã de -3,0 MPa. Quando o clone 120 foi usado como porta-enxerto, as plantas apresentaram sistema radicular mais profundo, mas com menor massa, retardaram por mais tempo a desidratação celular das folhas e apresentaram maior eficiência no uso da água. Sob seca severa, os teores de amido e sacarose decresceram em todos os tratamentos, enquanto os teores de glicose, frutose, aminoácidos totais e prolina aumentaram, particularmente nos tratamentos 109A pé-franco, 109A/109A e 120/109A. Essas plantas apresentaram menor eficiência no uso da água. O acúmulo de solutos não foi associado à tolerância à seca. O uso de porta-enxertos tolerantes à seca contribui para a maior tolerância das plantas ao deficit hídrico.The objective of this work was to determine alterations in physiology and those due to drought tolerance on Conilon coffee (Coffea canephora) contrasting clones regarding the sensitivity to hydric stress. The reciprocal grafting between clones 109A, drought sensitive, and 120, drought tolerant, – 120/109A, 120/120, 109A/120, 109A/109A – along with their ungrafted control plants (109A and 120) were evaluated. Plants were cultivated in 12-L vases in greenhouse. Six months after grafting, half of the plants was subjected to water deficit, by suspending irrigation until leaves reached the hydric potential of -3,0 MPa. When clone 120 was used as rootstock, plants presented deeper roots, although with lower root-biomass, higher ability to postpone leaf dehydration and higher instantaneous water-use efficiency (WUE). Under severe drought, starch and sucrose contents decreased similarly, regardless of the treatment, whereas leaf concentrations of glucose, fructose, total amino acids and proline were higher in non-grafted 109A, 109A/109A, and 120/109A plants. These plants showed the lowest WUE values. Solute accumulation was not primarily related to drought tolerance. The use of drought tolerant rootstocks improves to drought tolerance in coffee

Inducing flowering in Noccaea caerulescens (J. & C. Presl) F. K. Mey (Brassicaceae), a species having high heavy-metal accumulation

Noccaea caerulescens (J. & C. Presl) F. K. Mey (Brassicaceae) is a plant widely used in studies of the high accumulation of such metals as Cd, Ni, and Zn. Considered a biennial species, propagated mainly by seed, it presents a long period for the generation of new individuals, which significantly hampers the development of new studies of this species. Based on the above, the objective of this work was to develop a protocol to induce early flowering and abundant seed-production in N. caerulescens. Plants of this species were therefore grown and developed in a controlled environment (growth room and cold chamber), and then submitted to different treatments composed of combinations of the following environmental conditions: photoperiod (8 or 12 hour of light - 100 µmol m-2 s-1), temperature (4 or 21 °C), time of exposure to the above conditions (6 or 8 weeks) and application of different concentrations of GA3 (0, 15, 30 and 60 µg µL-1). The work was carried out in a completely randomized design, with twenty plants per treatment being analyzed. The following characteristics were evaluated: a) Percentage of flowering (%); (b) Length of main cluster (cm); and (c) seed production (g pl-1). It can be seen that the temperature of 4ºC was essential for inducing flowering and seed-production in N. caerulescens, with the time of exposure of the plants to this temperature being very important to potentialise seed production and longer periods of exposure to low temperatures being preferredNoccaea caerulescens (J. & C. Presl) F. K. Mey (Brassicaceae) é uma planta muito utilizada em estudos de hiperacumulação de metais como Cd, Ni e Zn. Considerada espécie bienal, sendo propagada basicamente por sementes, apresenta longo período de tempo para a geração de novos indivíduos, o que prejudica consideravelmente o desenvolvimento de novos estudos com esta espécie. Baseado no exposto objetivou-se neste trabalho, o desenvolvimento de um protocolo para indução de florescimento precoce e abundante de N. caerulescens. Para isso, plantas desta espécie foram crescidas e desenvolvidas em ambiente controlado (sala de crescimento e câmara fria), sendo então submetidas a diferentes tratamentos que eram compostos por combinações de diferentes condições ambientais: fotoperíodo (8 ou 12 horas de luz - 100 µmol m-2 s-1), temperatura (4 ou 21 ºC), semanas de exposição às condições de luz e temperatura citadas anteriormente (6 ou 8 semanas) e aplicação de concentrações de GA3 (0; 15; 30 e 60 µg µL-1). O trabalho foi conduzido em delineamento inteiramente casualizado, sendo analisadas vinte plantas por tratamento. As seguintes características foram avaliadas: a) Percentual de florescimento (%); b) Comprimento do pendão principal (cm); e c) Produção de sementes (g pl-1). Pode-se observar que a temperatura de 4 ºC foi essencial para a indução ao florescimento e produção de sementes de N. caerulescens, sendo que o tempo de exposição das plantas a esta, foi muito importante para a potencialização da produção de sementes, sendo desejados períodos mais longos de exposição à baixa temperatura

Inducing flowering in Noccaea caerulescens (J. & C. Presl) F. K. Mey (Brassicaceae), a species having high heavy-metal accumulation

Noccaea caerulescens (J. & C. Presl) F. K. Mey (Brassicaceae) is a plant widely used in studies of the high accumulation of such metals as Cd, Ni, and Zn. Considered a biennial species, propagated mainly by seed, it presents a long period for the generation of new individuals, which significantly hampers the development of new studies of this species. Based on the above, the objective of this work was to develop a protocol to induce early flowering and abundant seed-production in N. caerulescens. Plants of this species were therefore grown and developed in a controlled environment (growth room and cold chamber), and then submitted to different treatments composed of combinations of the following environmental conditions: photoperiod (8 or 12 hour of light - 100 µmol m-2 s-¹), temperature (4 or 21 °C), time of exposure to the above conditions (6 or 8 weeks) and application of different concentrations of GA3 (0, 15, 30 and 60 µg µL-1). The work was carried out in a completely randomized design, with twenty plants per treatment being analyzed. The following characteristics were evaluated: a) Percentage of flowering (%); (b) Length of main cluster (cm); and (c) seed production (g pl-1). It can be seen that the temperature of 4ºC was essential for inducing flowering and seed-production in N. caerulescens, with the time of exposure of the plants to this temperature being very important to potentialise seed production and longer periods of exposure to low temperatures being preferred

A new species of Gymnogeophagus Miranda Ribeiro from Uruguay (Teleostei: Cichliformes)

We describe a new species of a substrate-brooding Gymnogeophagus, based on coloration characters. The new species can be distinguished from the remaining substrate-brooding species in the genus by the unique pigmentation of the dorsal fin which consists of light blue, diagonal stripes over a red background in the spiny section and a combination of round, elliptic, and elongated bright blue spots over a red background in the soft section. It can be further distinguished from all other species of Gymnogeophagus by the following combination of characters: a discontinuous bright blue band above the upper lateral line in the humeral area, light blue roundish spots over a red to orange background on the anal fin, and conspicuous bright blue horizontal bands on body. The new species inhabits a wide range of freshwater habitats in the lower rio Uruguay basin, Rio de la Plata coastal drainages and Atlantic Ocean coastal drainages in Uruguay.Describimos una nueva especie de Gymnogeophagus con incubación de sustrato, en base a caracteres cromáticos. La nueva especie puede ser diferenciada de las restantes especies del género por la exclusiva pigmentación de la aleta dorsal, la que consiste de bandas oblicuas de color celeste sobre fondo rojo en la porción espinosa y una combinación de manchas redondas, elípticas, o alargadas azul brillantes sobre fondo rojo en la porción blanda. Además puede ser distinguida de las otras especies de Gymnogeophagus por la siguiente combinación de caracteres: banda horizontal azul iridiscente situada por encima de la línea lateral superior discontinua en la región humeral, manchas azules brillantes redondeadas sobre fondo rojo anaranjado en la aleta anal, bandas horizontales azul brillante en el cuerpo conspicuas. La nueva especie habita una amplia gama de hábitats de agua dulce en el sector inferior de la cuenca del río Uruguay, los drenajes costeros del Río de la Plata y drenajes costeros del Océano Atlántico en Uruguay

Expressão de genes da subfamília HD-Zip I em soja submetida à seca

O objetivo deste trabalho foi identificar genes candidatos da subfamília de fatores transcricionais HD-Zip I que contribuem para a tolerância à seca em soja. Foram avaliados trifólios de soja de cultivar tolerante (Embrapa 48) e suscetível à seca (BR 16), sob três níveis de deficit hídrico: ausência, moderado (-1,5 MPa) e severo (-3,0 MPa). Pela análise dos promotores, foi identificada a presença de possíveis elementos cis-regulatórios relacionados à resposta à seca, nos três genes avaliados (GmHB6, GmHB13 e GmHB21). No entanto, não houve padrão de distribuição específico associado à maior tolerância do genótipo à seca. Com a análise comparativa, foram identificados seis elementos cis-regulatórios potencialmente envolvidos na indução da expressão gênica sob seca. O gene GmHB13 foi exclusivamente induzido pela seca no genótipo tolerante, e o gene GmHB6 apresentou redução da expressão somente no genótipo suscetível. Já o gene GmHB21, apresentou aumento da expressão em ambos os genótipos. O gene GmHB13 é um importante elemento na regulação do mecanismo de tolerância à seca em soja, na cultivar tolerante Embrapa 48.The objective of this work was to identify candidate genes of the HD-Zip I transcription factors subfamily that contribute to drought tolerance in soybean. Trifoliate soybean leaves of drought tolerant (Embrapa 48) and susceptible (BR 16) cultivars were evaluated under three levels of drought: absence, moderate (-1.5 MPa), and severe (-3.0 MPa). Promoter analysis indicated the presence of putative cis-regulatory elements related to water stress in the three genes evaluated (GmHB6, GmHB13, and GmHB21). However, there was no specific pattern of distribution associated with the higher drought tolerance of the genotype. By comparative analysis, six cis-regulatory elements potentially involved in the induction of gene expression under drought were identified. Gene GmHB13 was exclusively induced by drought in the tolerant cultivar, and GmHB6 had its expression reduced only in the susceptible cultivar. Gene GmHB21 showed increased expression in both genotypes. Gene GmHB13 is an important element in the regulation of the drought tolerance mechanism in soybean, in the tolerant cultivar Embrapa 48