Differential expression of the ascorbate oxidase multigene family of Camellia sinensis in response to stress

Apoplastic ascorbate oxidase (AO) plays a major role in cell growth. Although AO genes have been studied in depth, some articles have mistakenly identified AO homologues as AO genes. Overall, the divergence between AO genes and AO homologues has not been explored. Meanwhile, there is little information concerning AO and the AO homologue with respect to Camellia sinensis. In the present study, one CsAO homologue and three CsAOs were confirmed by RT-PCR amplification, cloning and sequencing. Multicopper oxidase type 1 (PF00394), type 2 (PF07731) or type 3 (PF07732) domains and one transmembrane helix were the key domains for each member of the cupredoxin family. The CsAOs with their counterparts from seven dicotyledonous plants and three monocotyledonous plants were used to build phylogenetic tree and compare the deduced polypeptides. CsAO may be strongly expressed in the stretch expanded tissues, including bud and root. The abiotic stress-induced expression pattern of the CsAO homologue (CsAO2) is similar to those of CsAO1, CsAO3 and CsAO4. A new and very large group of AO homologues, which may function as AO genes, was present in both dicotyledonous and monocotyledonous plants. Our study may help in identifying stress-responsive AO genes of plants.     

小麦叶片衰老过程中CAT和APX活力及其同工酶谱的变化

小麦叶片在连体自然衰老和离体诱导衰老过程中，过氧化氢酶（ＣＡＴ）活力比抗坏血酸过氧化物酶（ＡＰＸ）活力下降得早。当ＣＡＴ活力处于较低水平时，ＡＰＸ仍然维持较较活力，且ＡＰＸ活力与Ｈ２Ｏ２含量呈显著负相关，经同工酶电泳分析，离体叶片暗诱导衰老过程中，ＣＡＴ同工酶带无增减，只是活性免疫，而ＡＰＸ同工酶带则有增加，ＡＰＸ在小麦叶片衰老的中后期可能起着比ＣＡＴ更重要的清除Ｈ２Ｏ２的作用。     

家蝇幼虫体内过氧化物酶过氧化氢酶抗坏血酸过氧化物酶与抗药性的关系——I.H_2O_2对酶活性的影响

采用室内饲养试验方法，研究了H2O2对家蝇幼虫体内过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(AsA—POD)活性的影响。结果表明，外源H2O2能不同程度地影响以上3种酶的活性，但变化规律却有明显差异：CAT活性变化的基本趋势是随着龄期的增加而递增，处理组最大值分别是对照组的1．2、1．26、1．47倍，另外在1、2龄幼虫中CAT活性出现了对照比处理高的现象，而3龄幼虫则没有出现。经H2O2处理后的1、3龄幼虫体内的POD出现了2个活性峰，1龄幼虫被处理后，在第1个活性峰出现的时间内对照明显比处理高，且持续时间约为5h，然后酶活性骤然上升，活性高峰值是对照组的6．8倍；2龄幼虫只有1个活性峰，是对照组的3．68倍；3龄幼虫体内的POD也有2个活性峰出现，分别是对照组的4．9、2倍。AsA—POD活性在整个实验过程中没有出现对照高于处理的现象，1、2龄幼虫经过处理后出现了2个活性峰，分别是对照组的1．3、1．3倍和2．08、1．73倍，3龄幼虫则只有1个活性峰，是对照组的1．8倍。     

对猪血品质影响的研究

通过近年多次试验，对猪血短期贮存的护色效果进行了研究．结果表明，在猪血中加入抗氧化剂──抗坏血酸钠2g／L和发色助剂──烟酰胺0．5g／L，在0—5℃环境中贮存2～4d效果最佳．并研究证实亚硝酸钠不能作为猪血发色剂使用．     

Interaction of Ph and Mn on Physiological Parameters of Brassica Oleracea L.

In the present study, interaction of 4 levels of manganese (Mn²⁺) (0, 100, 200, and 400 mM) and 4 levels of pH (4.5, 5.5, 6.5, and 7.5) were investigated on some physiological parameters of Brassica oleracea L. after 30 days of growth (15 days treatment) in hydroponic culture. Results showed that with an increase in manganese concentration, soluble carbohydrates, protein, and ascorbate contents also increased in shoots and roots of Brassica oleracea L. However, higher concentration of manganese reduced soluble carbohydrates, protein and ascorbate contents in the same plant. As manganese concentration increased, catalase activity in roots and shoots was also remarkably increased. Moreover, root peroxidase activity at pH 4.5 increased with an increase in manganese concentration and this increase was highest at pH 4.5 and 400 mM manganese concentration.     

Catalase and ascorbate peroxidase activities are not directly involveded in the silicon‐mediated alleviation of ferrous iron toxicity in rice

Silicon (Si) is the second most abundant element in the soil and can alleviate several abiotic stresses in many plant species. However, the mechanisms involved in alleviating ferrous iron (Fe²⁺) toxicity by Si are still largely unknown, and no study has investigated the role of Si on the Fe²⁺‐induced oxidative stress and antioxidant system in rice. Four cultivars of Asian and African rice (Oryza sativa L. and Oryza glaberrima Steud) were grown for 4 weeks under hydroponic conditions with or without Fe²⁺ (250 mg Fe²⁺ L^?1) and with or without Si (250 mg SiO₂ L^?1). The plants that were treated with Fe²⁺ suffered Fe²⁺ toxicity, and Si helped to alleviate the toxicity symptoms. The bronzing index and the Fe concentration in the foliar tissue increased in the presence of Fe²⁺ but decreased significantly with the application of 250 mg SiO₂ L^?1. The concentration of malonyldialdehyde, that is commonly used as an indicator of oxidative stress, increased in the foliar tissue in the presence of 250 mg Fe²⁺ L^?1 in the nutrient solution. The application of 250 mg SiO₂ L^?1 in the plant nutrient solution treated with Fe²⁺ considerably limited the increase of malonyldialdehyde. However, no significant effect of Si application on the activities of antioxidant enzymes (catalase and ascorbate peroxidase) and non‐enzymatic antioxidants (total ascorbate, reduced ascorbate, oxidized ascorbate, and the ratio of the reduced to oxidized forms) was observed in the rice plants that were grown in the presence of Fe²⁺. These results suggest that Si does not act directly on the antioxidant defense system of rice but reduces the plant Fe²⁺ concentration, which reduces the oxidative stress.     

Phytotoxicity of Roundup Ultra 360 SL in aquatic ecosystems: Biochemical evaluation with duckweed (Lemna minor L.) as a model plant

Glyphosate-based herbicides (e.g. Roundup Ultra 360 SL) are extensively used in aquatic environment. Although glyphosate is more environmental favorable than many other herbicides, it may be exceptionally dangerous for aquatic ecosystems through high water solubility. Thus, the aim of the work was quantification of influence of Roundup Ultra 360 SL (containing isopropylamine salt of glyphosate as an active ingredient) on biomass and chlorophyll content within duckweed (Lemna minor L.). Moreover, changes in polyamine content and activity of such antioxidative enzymes as catalase (CAT) and ascorbate peroxidase (APX) were assayed in order to determine the biochemical mechanisms of L. minor response to the herbicide treatment. Obtained results showed that phytotoxicity of the herbicide was connected with decrease in chlorophyll-a, b and a+b content, and reduction of biomass growth. Roundup, similarly to some abiotic and biotic stressors, caused over-accumulation of putrescine, spermidine and total polyamines (PAs) within duckweed tissues. In addition an increase in CAT and APX activities suggested that stress generated by the herbicide treatment was at least partially connected with oxidative burst. Intensity of the duckweed responses to the herbicide was dependent on the applied herbicide level and/or duration of treatment.     

Antioxidative activity associated with chilling injury tolerance of muskmelon (Cucumis melo L.) rind

‘Galia’ melon (Cucumis melo L. var. reticulatus) is a climacteric fruit with a short storage life. To prevent over-ripening, fruits are stored at 4–6 °C, which also results in chilling injury (CI) that appears as numerous brown spots on the surface of the fruit. It has been suggested that exposure of ‘Galia’ fruits to high growth temperatures in the field renders them sensitive to low storage temperatures. Activity profile of the antioxidative enzymes catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and glutathione reductase (GR) was monitored in the rind of ‘Galia’ fruits during low-temperature storage, to associate each enzyme's activity with CI incidence. Experiments were performed with low-temperature-sensitive and tolerant varieties, 5080^S and 1537^T respectively, and included a pre-storage treatment of hot-water wash of 5080^S fruits.     

FOLIAR SPRAYS OF PHOTOSYNTHETIC BACTERIA IMPROVE THE GROWTH AND ANTI-OXIDATIVE CAPABILITY ON CHINESE DWARF CHERRY SEEDLINGS

Recently, there has been increasing attempts for photosynthetic bacteria (PSB) as foliar fertilizer in China. The biomass, net photosynthetic rate (Pn), maximal photochemical efficiency of PS II(Fv/Fm) and antioxidant isoenzymes metabolism were examined in Chinese dwarf cherry (Prunus humilis Bunge) seedlings with or without exogenous PSB application in this study. PSB sprays resulted in a significant accumulation of fresh weight and leaf area of Chinese dwarf cherry plants, accompanying with a marked increase of Pn. However, Fv/Fm had negligible changes. The exogenous PSB also induced the activities of superoxide dismutase (SOD) and ascorbate peroxidase (APX), and a general increase of their isoenzymes activities. The increased level was the most significant in chloroplasts [such as Cu/Zn-SOD, Fe-SOD and stroma APX (sAPX)]. Our results demonstrated that PSB played a favorable role in growth and photosynthesis and improved the antioxidative capability in plants.     

Seed Priming with Ascorbic Acid Improves Drought Resistance of Wheat

The study, consisting of two independent experiments, was conducted to evaluate the role of seed priming with ascorbic acid (AsA) in drought resistance of wheat. In the first experiment, seeds of wheat cultivars Mairaj‐2008 and Lasani‐2008 were either soaked in aerated water (hydropriming) for 10 h or not soaked (control). In the second experiment, seeds of same wheat cultivars were soaked in aerated (2 mm ) AsA solution (osmopriming) or water (hydropriming) for 10 h. In both experiments, seeds were sown in plastic pots (10 kg) maintained at 70 % and 35 % of water‐holding capacity designated as well watered and drought stressed, respectively. Both experiments were laid out in a completely randomized design with six replications. Drought caused delayed and erratic emergence and disturbed the plant water relations, chlorophyll contents and membranes because of oxidative damage; however, root length in cultivar Lasani‐2008 was increased under drought. Hydropriming significantly improved the seedling emergence and early growth under drought and well‐watered conditions; however, improvement was substantially higher from osmopriming with AsA. Similarly, osmopriming with AsA significantly improved the leaf emergence and elongation, leaf area, specific leaf area, chlorophyll contents, root length and seedling dry weight. Owing to increase in proline accumulation, phenolics and AsA, by seed priming with AsA, plant water status was improved with simultaneous decrease in oxidative damages. These improved the leaf emergence and elongation, and shoot and root growth under drought. However, there was no difference between the cultivars in this regard. In conclusion, osmopriming with AsA improved the drought resistance of wheat owing to proline accumulation and antioxidant action of AsA and phenolics, leading to tissue water maintenance, membrane stability, and better and uniform seedling stand and growth.