Exogenous nitric oxide improves sugarcane growth and photosynthesis under water deficit

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Nitric oxide (NO)-mediated redox signaling plays a role in alleviating the negative impact of water stress in sugarcane plants by improving root growth and photosynthesis. Drought is an environmental limitation affecting sugarcane growth and yield. The redox-active molecule nitric oxide (NO) is known to modulate plant responses to stressful conditions. NO may react with glutathione (GSH) to form S-nitrosoglutathione (GSNO), which is considered the main reservoir of NO in cells. Here, we investigate the role of NO in alleviating the effects of water deficit on growth and photosynthesis of sugarcane plants. Well-hydrated plants were compared to plants under drought and sprayed with mock (water) or GSNO at concentrations ranging from 10 to 1000 mu M. Leaf GSNO sprayed plants showed significant improvement of relative water content and leaf and root dry matter under drought compared to mock-sprayed plants. Additionally, plants sprayed with GSNO (a parts per thousand yen 100 mu M) showed higher leaf gas exchange and photochemical activity as compared to mock-sprayed plants under water deficit and after rehydration. Surprisingly, a raise in the total S-nitrosothiols content was observed in leaves sprayed with GSH or GSNO, suggesting a long-term role of NO-mediated responses to water deficit. Experiments with leaf discs fumigated with NO gas also suggested a role of NO in drought tolerance of sugarcane plants. Overall, our data indicate that the NO-mediated redox signaling plays a role in alleviating the negative effects of water stress in sugarcane plants by protecting the photosynthetic apparatus and improving shoot and root growth.2441181190Sao Paulo Research Foundation (FAPESP, Brazil) [2008/57519-2]National Council for Scientific and Technological Development (CNPq, Brazil)[2012/19167-0][2015/00393-8]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Evidence towards the involvement of nitric oxide in drought tolerance of sugarcane

© 2017 Elsevier Masson SAS Exogenous supply of nitric oxide (NO) increases drought tolerance in sugarcane plants. However, little is known about the role of NO produced by plants under water deficit. The aim of this study was to test the hypothesis that drought-tolerance in sugarcane is associated with NO production and metabolism, with the more drought-tolerant genotype presenting higher NO accumulation in plant tissues. The sugarcane genotypes IACSP95-5000 (drought-tolerant) and IACSP97-7065 (drought-sensitive) were submitted to water deficit by adding polyethylene glycol (PEG-8000) in nutrient solution to reduce the osmotic potential to−0.4MPa. To evaluate short-time responses to water deficit, leaf and root samples were taken after 24h under water deficit. The drought-tolerant genotype presented higher root extracellular NO content, which was accompanied by higher root nitrate reductase (NR) activity as compared to the drought-sensitive genotype under water deficit. In addition, the drought-tolerant genotype had higher leaf intracellular NO content than the drought-sensitive one. IACSP95-5000 exhibited decreases in root S-nitrosoglutathione reductase (GSNOR) activity under water deficit, suggesting that S-nitrosoglutathione (GSNO) is less degraded and that the drought-tolerant genotype has a higher natural reservoir of NO than the drought-sensitive one. Those differences in intracellular and extracellular NO contents and enzymatic activities were associated with higher leaf hydration in the drought-tolerant genotype as compared to the sensitive one under water deficit

Effects of storage time and freeze-drying on the activity of antioxidant enzymes in sugarcane leaves

The analysis of the antioxidant enzymatic system in leaves is usually done in samples frozen and stored in ultrafreezer. The freeze-drying technique could be an alternative for preserving samples for long time, but the influence of this procedure on antioxidant enzymes is not known. This study aimed to evaluate the influence of storage time and freeze-drying on the activity of antioxidant enzymes of sugarcane leaves. Samples were collected, immersed in liquid nitrogen and stored at −80 °C. The activities of superoxide dismutase, catalase, total peroxidase, ascorbate peroxidase, and the protein content were determined on the sampling day and after 27 and 53 days of storage. The activity of antioxidant enzymes as well as the leaf protein concentration remained unchanged after 53 days of storage. However, significant decreases in the activity of all enzymes and in protein content were caused by the freeze-drying technique. Our data revealed that (i) sugarcane leaves can be stored in ultrafreezer for almost 2 months without losing enzymatic activity or protein content and (ii) the freeze-drying technique should not be used to preserve samples for further analysis of antioxidant enzymes39373376CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPnão tem2008/57519-2; 2012/19167-0; 2014/13524-

Encapsulation of s-nitrosoglutathione into chitosan nanoparticles improves drought tolerance of sugarcane plants

The entrapment of NO donors in nanomaterials has emerged as a strategy to protect these molecules from rapid degradation, allowing a more controlled release of NO and prolonging its effect. On the other hand, we have found beneficial effects of S-nitrosoglutathione (GSNO) - a NO donor - supplying to sugarcane plants under water deficit. Here, we hypothesized that GSNO encapsulated into nanoparticles would be more effective in attenuating the effects of water deficit on sugarcane plants as compared to the supplying of GSNO in its free form. The synthesis and characterization of chitosan nanoparticles containing GSNO were also reported. Sugarcane plants were grown in nutrient solution, and then subjected to the following treatments: control (well-hydrated); water deficit (WD); WD + GSNO sprayed in its free form (WDG) or encapsulated (WDG-NP). In general, both GSNO forms attenuated the effects of water deficit on sugarcane plants. However, the encapsulation of this donor into chitosan nanoparticles caused higher photosynthetic rates under water deficit, as compared to plants supplied with free GSNO. The root/shoot ratio was also increased when encapsulated GSNO was supplied, indicating that delayed release of NO improves drought tolerance of sugarcane plants. Our results provide experimental evidence that nanotechnology can be used for enhancing NO-induced benefits for plants under stressful conditions, alleviating the negative impact of water deficit on plant metabolism and increasing biomass allocation to root system843844CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPSem informação2008/57519-2; 2016/10347-6; 2018/08194-2; 2012/19167-0; 2015/00393-

Nitric oxide attenuates oxidative stress induced by arsenic in lettuce (Lactuca sativa) leaves

Lettuce plants were exposed to different toxic levels of arsenic (As) to induce an oxidative stress response, and the role of nitric oxide (NO) (provided as sodium nitroprusside (SNP)) as an attenuating agent of this stress condition was evaluated. Plants were treated with 50 μM of As with or without 100 μM SNP added to the nutrient solution. The hydrogen peroxide, superoxide anion, and malondialdehyde concentrations and enzymatic activities were measured. The increase in As concentration detected in the leaves was followed by a significant increase in H2O2 and malondialdehyde (MDA) concentrations. However, the presence of SPN promoted a reduction in the concentration of these oxidative agents and also reduced the translocation of As to the shoots. The enzymatic activities in the plants exposed to As were increased, which indicates the active participation of these enzymes in the reduction of oxidative stress induced by the metalloid. In the plants exposed to As and SNP, the enzymatic activities were not so high; this result was possibly related to the direct action of NO in scavenging the generated toxic metabolites and with the reduction in the translocation of the pollutant to the shoots. Lettuce and leaves of other vegetables are usually ingested, and this study shows an alternative to avoid human contamination with As

Uptake arsenic by plants: Effects on mineral nutrition, growth and antioxidant capacity

Arsenic (As) is the one of the main environmental pollutant and phytoremediation is an effective tool for its removal of the environment. In this study, Pistia stratiotes were exposed to seven As concentrations (0, 3, 7, 10, 13, 16 and 20 μM) and then, the influence of this metalloid on growth, mineral nutrition and photosynthesis were analyzed. It was observed that this species have a high affinity for As and pollutant uptake occurs rapidly. The uptake of Cu, Mn, Fe and P increased until the concentration of 13 μM, decreasing in higher concentrations.The Mg content also decreased from this same concentration. No effects were observed in the uptake of K, Ca and Zn. Growth rate and photosynthetic pigments content were negatively affected by As. Despite this decrease, the growth was maintained up to the concentration of 13 μM of As. The maintenance of growth and the change in nutrients uptake are probably related with the increase in antioxidant capacity of the plant, indicating resistance to the pollutant. In this way, P. stratiotes is probably an efficient phytoremediator of As, even when in concentrations up to one hundred times greater than those permitted in water for human consumption.El Arsénico (As) es uno de los principales contaminantes ambientales y la fitorremediación se presenta como una herramienta efectiva para retirar este elemento del medio ambiente. En el presente estudio se analizó la influencia de este elemento en el crecimiento, nutrición mineral y fotosíntesis de Pistia stratiotes bajo siete concentraciones de As (0, 3, 7, 10, 13, 16 y 20 μM). Encontrándose gran afinidad de esta especie por el As, siendo que la absorción de este elemento ocurre deforma rápida afectando la absorción de nutrientes esenciales. En este sentido, la absorción de Cu, Mn, Fe y P aumentó hasta una concentración de 13 μM de As, disminuyendo en el caso de las mayores concentraciones, entre tanto se observó una disminución en la absorción de Mg. No fueron observados efectos sobre la absorción de K, Ca y Zn. A pesar que tanto la fotosíntesis como el crecimiento fueron negativamente afectados por las diferentes concentraciones de As la planta consiguió mantener una tasa reducida de crecimiento hasta la concentración de 13 μM. Esta situación así como las alteraciones observadas en la absorción de nutrientes, probablemente esté relacionada con el aumento en la capacidad antioxidativa de la planta, indicando una posible respuesta de resistencia de la planta frente a este elemento contaminante. De esta forma es probable concluir que P. stratiotes actúa como una eficiente fitorre-mediadora de As, aun en concentraciones cien veces mayor que los niveles permitidos en el agua apta para consumo humano

Short-term physiological changes in roots and leaves of sugarcane varieties exposed to H2O2 in root medium

The aim of this study was to evaluate the differential sensitivity of sugarcane genotypes to H2O2 in root medium. As a hypothesis, the drought tolerant genotype would be able to minimize the oxidative damage and maintain the water transport from roots to shoots, reducing the negative effects on photosynthesis. The sugarcane genotypes IACSP94-2094 (drought tolerant) and IACSP94-2101 (drought sensitive) were grown in a growth chamber and exposed to three levels of H2O2 in nutrient solution: control; 3 mmol L−1 and 80 mmol L−1. Leaf gas exchange, photochemical activity, root hydraulic conductance (Lr) and antioxidant metabolism in both roots and leaves were evaluated after 15 min of treatment with H2O2. Although, root hydraulic conductance, stomatal aperture, apparent electron transport rate and instantaneous carboxylation efficiency have been reduced by H2O2 in both genotypes, IACSP94-2094 presented higher values of those variables as compared to IACSP94-2101. There was a significant genotypic variation in relation to the physiological responses of sugarcane to increasing H2O2 in root tissues, being root changes associated with modifications in plant shoots. IACSP94-2094 presented a root antioxidant system more effective against H2O2 in root medium, regardless H2O2 concentration. Under low H2O2 concentration, water transport and leaf gas exchange of IACSP94-2094 were less affected as compared to IACSP94-2101. Under high H2O2 concentration, the lower sensitivity of IACSP94-2094 was associated with increases in superoxide dismutase activity in roots and leaves and increases in catalase activity in roots. In conclusion, we propose a general model of sugarcane reaction to H2O2, linking root and shoot physiological responses

Photosynthesis and biomass accumulation in young sugarcane plants grown under increasing ammonium supply in nutrient solution

The aim of this study was to evaluate the sugarcane responses to varying ammonium:nitrate (NH4+:NO3-) ratio and to reveal how much NH4+ plants can tolerate before showing impairment of photosynthesis and growth. Sugarcane plants were grown in nutrient solution with the following NH4+:NO3- ratios (%): 20:80; 30:70; 40:60; 60:40; 70:30; and 80:20. The lowest photosynthetic rates, stomatal conductance, instantaneous carboxylation efficiency and leaf chlorophyll a content were found in plants supplied with higher than 60% NH4+. The leaf content of chlorophyll b proved to be more sensitive than chlorophyll a and decreases were found from 40% NH4+. We did not observe significant differences in leaf NO3- concentration under varying NH4+:NO3- ratio. However, plants that received 80% NH4+ showed the highest leaf NH4+ concentration and lowest leaf [NO3-]:[NH4+] ratio. The estimated leaf nitrogen content was higher in plants supplied with 20% and 30% NH4+. Taken together, our data revealed that sugarcane plants are sensitive to NH4+, with photosynthesis and plant growth being impaired when NH4+ supply was higher than 30% in nutrient solution. Root biomass was significantly reduced under high NH4+ supply, which explains decreases in stomatal conductance. Besides stomatal limitation, photosynthesis was also limited by low carboxylation efficiency under high NH4+ supply. Apparently, leaf NH4+ concentrations higher than 1.0 mu mol g(-1) were enough to impair photosynthesis. The balance between [NO3-] and [NH4+] in leaves was more correlated to photosynthesis than either [NO3-] or [NH4+] alone313401411CAPES - Coordenação de Aperfeiçoamento de Pessoal e Nível SuperiorCNPQ - Conselho Nacional de Desenvolvimento Científico e TecnológicoFAPESP – Fundação de Amparo à Pesquisa Do Estado De São Paulonão temnão tem2017/11279-7MDP acknowledges the scholarship provided by the São Paulo Research Foundation (FAPESP, Brazil; Grant No. 2017/11279-7). NMS acknowledges the fellowship granted by the National Program of Post-Doctorate (PNPD), Coordination for the Improvement of Higher Education Personnel (Capes, Brazil). ECM, LS and RVR acknowledge the fellowships granted by the National Council for Scientific and Technological Development (CNPq, Brazil