Plants facing oxidative challenges—A little help from the antioxidant networks

Vigna unguiculata, one of the most important legumes, mainly in underdeveloped countries, is susceptible to post-harvest losses in storage by Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: Chrysomelidae). The work evaluated the toxicity, inhibition of oviposition, instantaneous rate of population growth (ri) and the development of fumigated C. maculatus with the essential oil of Vanillosmopsis arborea and its major constituent, α-bisabolol. The experimental units consisted of 0.8 L flasks treated with concentrations of 1.2–11.2 μL L−1of air of the essential oil of V. arborea or its major constituent applied to disks of filter paper. α-Bisabolol was quantified as 409.33 mL L−1 of the essential oil. The development rate of C. maculatus was evaluated by daily adult counts. Oviposition was evaluated at lethal concentrations (LC50, LC25, LC10 and LC1). The LC50 and LC95 of the essential oil of V. arborea and α-bisabolol were 5.23 and 12.97 μL L−1 of air and 2.47 and 8.82 μL L−1 of air, respectively. At some concentrations, the α-bisabolol was more toxic to males than to females of the insect. Increased concentrations of the essential oil reduced the ri, rate of development, oviposition, and number of eggs of C. maculatus and therefore have potential for pest control.

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Insecticidal activity of Vanillosmopsis arborea essential oil and of its major constituent α-bisabolol against Callosobruchus maculatus (Coleoptera: Chrysomelidae).

Mitochondrial glutathione peroxidase (OsGPX3) has a crucial role in rice protection against salt stress

Retrograde signalling pathways that are triggered by changes in cellular redox homeostasis remain poorly understood. Transformed rice plants that are deficient in peroxisomal ascorbate peroxidase APX4 (OsAPX4-RNAi) are known to exhibit more effective protection of photosynthesis against oxidative stress than controls when catalase (CAT) is inhibited, but the mechanisms involved have not been characterized. An in-depth physiological and proteomics analysis was therefore performed on OsAPX4-RNAi CAT-inhibited rice plants. Loss of APX4 function led to an increased abundance of several proteins that are involved in essential metabolic pathways, possibly as a result of increased tissue H2O2 levels. Higher photosynthetic activities observed in the OsAPX4-RNAi plants under CAT inhibition were accompanied by higher levels of Rubisco, higher maximum rates of Rubisco carboxylation, and increased photochemical efficiencies, together with large increases in photosynthesis-related proteins. Large increases were also observed in the levels of proteins involved in the ascorbate/glutathione cycle and in other antioxidant-related pathways, and these changes may be important in the protection of photosynthesis in the OsAPX4-RNAi plants. Large increases in the abundance of proteins localized in the nuclei and mitochondria were also observed, together with increased levels of proteins involved in important cellular pathways, particularly protein translation. Taken together, the results show that OsAPX4-RNAi plants exhibit significant metabolic reprogramming, which incorporates a more effective antioxidant response to protect photosynthesis under conditions of impaired CAT activity.

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Impairment of peroxisomal APX and CAT activities increases protection of photosynthesis under oxidative stress.

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) play a pivotal role in the dynamic cell signaling systems in plants, even under biotic and abiotic stress conditions. Over the past two decades, various studies have endorsed the notion that these molecules can act as intracellular and intercellular signaling molecules at a very low concentration to control plant growth and development, symbiotic association, and defense mechanisms in response to biotic and abiotic stress conditions. However, the upsurge of ROS and RNS under stressful conditions can lead to cell damage, retarded growth, and delayed development of plants. As signaling molecules, ROS and RNS have gained great attention from plant scientists and have been studied under different developmental stages of plants. However, the role of RNS and RNS signaling in plant–microbe interactions is still unknown. Different organelles of plant cells contain the enzymes necessary for the formation of ROS and RNS as well as their scavengers, and the spatial and temporal positions of these enzymes determine the signaling pathways. In the present review, we aimed to report the production of ROS and RNS, their role as signaling molecules during plant–microbe interactions, and the antioxidant system as a balancing system in the synthesis and elimination of these species. 

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The Key Roles of ROS and RNS as a Signaling Molecule in Plant–Microbe Interactions

Toxicity caused by high concentrations of ascorbic acid (AA) has been widely reported in animal cells but is scarcely described in plants. In this study, rice plants deficient (knockdown) in two chloroplast ascorbate peroxidases (APX7/8) and non-transformed (NT) were exposed to wide exogenous AA concentrations in the presence of low light and high light (HL). Reduced (ASC) and oxidized (DHA) ascorbate reached much higher concentrations in symplast compared to the apoplastic space, and high redox states were found in both cellular compartments. Exogenous AA concentrations above 30 mM caused strong cellular and oxidative damage indicated by decreased cell integrity and increased lipid peroxidation in leaves. These toxic effects were strongly enhanced by HL and, to a small extent, by deficiency of both chloroplastic proteins APX7/8. The combination of HL and high AA concentration induced a strong increase in H2O2, associated with decrease in the content of chlorophylls and carotenoids. High AA concentrations strongly induced stomatal closure and impairment in CO2 assimilation, in combination with decreased quantum efficiency of photosystem II (PSII) and PSI. We postulate that oxidative stress caused by AA toxicity in the presence of HL was induced by over-production of reactive oxygen species due to an imbalance between excess energy in the photosystems and low CO2 assimilation, which was related closely to strong decrease in stomatal conductance. In addition, high ASC levels might have acted as a pro-oxidant in the presence of high H2O2 concentrations, stimulating the Fenton reaction and contributing to the intensification of oxidative stress in rice leaves.

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Ascorbic acid toxicity is related to oxidative stress and enhanced by high light and knockdown of chloroplast ascorbate peroxidases in rice plants

Introducao: Vanillosmopsis arborea e uma especie medicinal nativa da Floresta Nacional do Araripe, Ceara, cujo oleo essencial e rico em alfa bisabolol, que apresenta atividades antibacteriana, antifungica e antiinflamatoria. Objetivos: verificar a influencia da altura da planta e do diâmetro dos ramos do candeeiro sobre o teor e rendimento do seu oleo essencial, identificar seus constituintes e seu efeito alelopatico sobre a alface ( L. sativa L.) e repolho ( B. oleracea var. capitata L.). Metodos: ramos secundarios de plantas nativas de V. arborea Baker com altura media de 1,80; 3,70 e 6,0 m passaram por processo de hidrodestilacao para analisar o teor e rendimento de seu oleo essencial. Da mesma forma para o experimento avaliando o diâmetro dos ramos de aproximadamente 3,0; 5,0 e 8,0 cm. Foi realizada analise da composicao quimica do oleo essencial e avaliada a sua acao alelopatica. Resultados: nao houve efeito da altura das plantas (1,8; 3,7 e 6 m) sobre o teor e rendimento de oleo essencial. Ramos com diâmetro intermediario de 5,0 cm apresentaram maior quantidade de oleo essencial. A analise cromatografica do oleo essencial permitiu identificar 10 constituintes quimicos, sendo que o sesquiterpeno alfa bisabolol foi o constituinte encontrado em maior quantidade (93,83 %). Conclusoes: houve influencia do diâmetro dos ramos sobre o teor e rendimento de oleo essencial. O sesquiterpeno alfa bisabolol foi o constituinte majoritario do oleo essencial de candeeiro. O oleo essencial nao apresentou acao alelopatica sobre a as especies avaliadas, sendo necessarios novos ensaios com o uso de maiores concentracoes deste oleo.

http://scielo.sld.cu/pdf/pla/v20n1/pla12115.pdf

Teor, rendimento e qualidade do óleo essencial de Vanillosmopsis arbórea (Gardner) Baker (candeeiro) e sua ação alelopática

Esta pesquisa teve como objetivo caracterizar os municipios de Crato, Barbalha e Missao Velha no que se refere a atividade agricola. Com o auxilio de formulario, socioeconomico, tecnologico e de informacoes fornecidas pela Empresa de Assistencia Tecnica e Extensao Rural do Ceara (EMATERCE), foi realizada uma pesquisa amostral em 169 propriedades rurais de pequeno e medio porte, classificadas em tres grupos, agricultura de subsistencia + fruticultura, subsistencia e hortalicas. O grupo que teve como atividades principais a agricultura de subsistencia + fruticultura correspondeu a 42% do total e apresentou um predominio de consorcio entre milho e feijao ou milho e fava, ja quanto as frutiferas observou-se um predominio de banana e goiaba. As condicoes de vida sao consideradas boas porem ainda ha pouca utilizacao de tecnologia na agricultura. A maioria dos produtores comercializa seus produtos, mas recomenda-se um maior incentivo dos orgaos competentes, atraves de assistencia tecnica, cursos sobre gerenciamento agricola e organizacao de produtores e maiores subsidios para melhoria da agricultura praticada nessas propriedades.

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Diagnóstico sócio-econômico e tecnológico do setor agrícola em alguns municípios da região do cariri cearense

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Antonio Glaydson de Sousa Feitosa

Papers

Ascorbic acid toxicity is related to oxidative stress and enhanced by high light and knockdown of chloroplast ascorbate peroxidases in rice plants

Teor, rendimento e qualidade do óleo essencial de Vanillosmopsis arbórea (Gardner) Baker (candeeiro) e sua ação alelopática

Diagnóstico sócio-econômico e tecnológico do setor agrícola em alguns municípios da região do cariri cearense

Contenido, rendimiento y la calidad del aceite esencial de árbol Vanillosmopsis arborea (Gardner) Baker (candeeiro) y su alelopatía

Content, Yield and quality of essential oil Vanillosmopsis arborea (Gardner) Baker (candeeiro) and its allelopathy