Boron Supply and Water Deficit Consequences in Young Paricá (Schizolobium parahyba var. amazonicum) Plants

Boron (B) is a very important nutrient required by forest plants; when supplied in adequate amounts, plants can ameliorate the negative effects of abiotic stresses. The objective of this study was to (i) investigate gas exchange, (ii) measure oxidant and antioxidant compounds, and (iii) respond how B supply acts on tolerance mechanism to water deficit in young Schizolobium parahyba plants. The experiment employed a factorial that was entirely randomised, with two boron levels (25 and 250 µmol L-1, simulating conditions of sufficient B and high B, respectively) and two water conditions (control and water deficit). Water deficit induced negative modifications on net photosynthetic rate, stomatal conductance and water use efficiency, while B high promoted intensification of the effects on stomatal conductance and water use efficiency. Hydrogen peroxide and electrolyte leakage of both tissues suffered non-significant increases after B high and when applied water deficit. Ascorbate levels presented increases after water deficit and B high to leaf and root. Our results suggested that the tolerance mechanism to water deficit in young Schizolobium parahyba plants is coupled to increases in total glutathione and ascorbate aiming to control the overproduction of hydrogen peroxide and alleviates the negative consequences on electrolyte leakage and gas exchange. In relation to B supply, this study proved that sufficient level promoted better responses under control and water deficit conditions

Expressão de genes de catalase e speróxido dismutase da mandioca durante interação com Phytopythium sp

Ministério da Educação, Universidade Federal Rural da Amazônia, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico e Fundação Amazônia Paraense de Amparo à Pesquisa.A cultura da mandioca possui grande importância mundial abastecendo cerca de 800 milhões de pessoas no mundo. No Brasil, o estado do Pará se destaca na produção desta cultura, a qual é cultivada principalmente por agricultores familiares o que garanti a sua subsistência por meio da comercialização e consumo dos seus derivados. No entanto, patógenos como o oomiceto Phytopythium sp. causador da podridão mole das raízes pode comprometer em até 100% a sua produção. Buscando entender a interação entre o Phytopythium sp. e a mandioca e os mecanismos envolvidos na resposta a nível molecular nesta interação, o objetivo desta pesquisa foi analisar as alterações nos níveis de expressão dos genes da catalase (CAT) e superóxido dismutase (SOD) em raízes destacadas de mandioca suscetíveis a infecção. Desta forma, neste trabalho, inicialmente foi realizada a busca por sequencias de genes da CAT e da SOD no genoma da mandioca disponível do Banco de Dados do Phytozome, o que resultou em 7 genes da CAT e 9 da SOD. Destes, foram selecionados 4 genes da CAT e 5 da SOD, para os quais foram determinadas as sequencias de iniciadores (primers) sintetizados. Em seguida, foram realizados ensaios de RT-PCR semi-quantitativa para avaliar os níveis de expressão destes genes em raízes destacadas de mandioca infectadas com Phytopythium sp. em comparação com o controle (raízes não infectadas). Foram observadas diferenças significativas tanto entre os tratamentos quanto no decorrer do tempo para cada tratamento, sendo as maiores expressões dos genes da SOD e da CAT no tempo de 48 hpi para o tratamento inoculado. Os resultados demonstram que a interação planta-patógeno aumentou a expressão dos genes estudados, podendo estes estarem envolvidos no mecanismo de defesa da planta, no entanto, estudos de análise funcional destes ainda precisam ser mais aprofundados, principalmente usando ensaios de superexpressão e perda de funções.Cassava culture is of great importance worldwide, supplying around 800 million people in the world. In Brazil, the state of Pará stands out in the production of this culture, which is mainly cultivated by family farmers, which guaranteed their subsistence through the marketing and consumption of their derivatives. However, pathogens such as the oomycete Phytopythium sp. cause of soft root rot can compromise its production by up to 100%. Seeking to understand the interaction between Phytopythium sp. and cassava and the mechanisms involved in the response at the molecular level in this interaction, the aim of this research was to analyze changes in the levels of expression of the catalase (CAT) and superoxide dismutase (SOD) genes in detached cassava roots susceptible to infection. Thus, in this work, the search for CAT and SOD gene sequences was initially carried out in the cassava genome available from the Phytozome Database, which resulted in 7 CAT and 9 SOD genes. Of these, 4 CAT and 5 SOD genes were selected, for which the sequences of synthesized primers were determined. Then, semiquantitative RT-PCR assays were performed to evaluate the levels of expression of these genes in detached cassava roots infected with Phytopythium sp. compared to the control (uninfected roots). Differences were observed between the treatment time intervals for each treatment, the largest being the SOD and CAT genes in the 48 hpi period for the inoculated treatment. The results demonstrate that the plant-pathogen interaction increased the expression of the studied genes, which may be involved in the plant's defense mechanism, however, studies of functional analysis of these still need to be further investigated, mainly using over expression and loss of function tests

Boron Supply and Water Deficit Consequences in Young Paricá (<i>Schizolobium parahyba</i> var.<i> amazonicum</i>) Plants

Boron (B) is a very important nutrient required by forest plants; when supplied in adequate amounts, plants can ameliorate the negative effects of abiotic stresses. The objective of this study was to (i) investigate gas exchange, (ii) measure oxidant and antioxidant compounds, and (iii) respond how B supply acts on tolerance mechanism to water deficit in young Schizolobium parahyba plants. The experiment employed a factorial that was entirely randomised, with two boron levels (25 and 250 µmol L-1, simulating conditions of sufficient B and high B, respectively) and two water conditions (control and water deficit). Water deficit induced negative modifications on net photosynthetic rate, stomatal conductance and water use efficiency, while B high promoted intensification of the effects on stomatal conductance and water use efficiency. Hydrogen peroxide and electrolyte leakage of both tissues suffered non-significant increases after B high and when applied water deficit. Ascorbate levels presented increases after water deficit and B high to leaf and root. Our results suggested that the tolerance mechanism to water deficit in young Schizolobium parahyba plants is coupled to increases in total glutathione and ascorbate aiming to control the overproduction of hydrogen peroxide and alleviates the negative consequences on electrolyte leakage and gas exchange. In relation to B supply, this study proved that sufficient level promoted better responses under control and water deficit conditions