Research on Oxalate Oxidase and Its Genes in Plants

This paper introduces the discovery,composition and structure of oxalate oxidase,as well as illustrates the biological functions of this enzyme.With a comprehensive introduction upon previous researches upon gene cloning and heredity transformation of this enzyme,it indicates that heredity transformation can increase the content of oxalate oxidase within the plants and also enhance their resistance.The paper also points out the problems such as lack of gene resources and difficulty in the transformation of heterologous genes,and the focus in later researches should be laid upon the exploration of plant resources relative to this enzyme and selection of resistant species.

Transgenic Arabidopsis thaliana expressing a wheat oxalate oxidase exhibits hydrogen peroxide related defense response

Oxalic acid（OA） is considered as an important pathogenetic factor of some destructive diseases caused by some fungal pathogens such as Sclerotinia sclerotiorum. Oxalate degradation is important for plant health, and plants that contain oxalate oxidase（OXO） enzymes could breakdown oxalate into CO_2 and H_2O_2, which subsequently evokes defense responses. However, some species, such as Arabidopsis thaliana, have no oxalate oxidase activity identified to date. The present study aims to develop transgenic Arabidopsis expressing a wheat oxalate oxidase, to test for the response to OA exposure and fungal infection by S. sclerotiorum. The results showed that the transgenic Arabidopsis lines that expressed the wheat OXO exhibited enhanced resistance to OA exposure and S. sclerotiorum infection in the tolerance assays. In the same manner, it could convert OA to CO_2 and H_2O_2 to a higher extent than the wild-type. Intensive osmotic adjustments were also detected in the transgenic Arabidopsis lines. The higher level of produced H_2O_2 subsequently induced an elevated activity of antioxidant enzymes including superoxide dismutase（SOD） and peroxidase（POD） in the transgenic Arabidopsis plants. The present study indicated that the expression of a gene encoding wheat OXO could induce intensive osmotic adjustments and hydrogen peroxide related defense response, and subsequently increased tolerance to S. sclerotiorum in transgenic A. thaliana.

Nanocapsules of oxalate oxidase for hyperoxaluria treatment

Enzyme therapeutics have great potential for the treatment of systemic disorders such as urolithiasis and nephrocalcinosis, which are caused by the excessive accumulation of oxalate. However, exogenous enzymes have short half-lives in vivo and elicit high immunogenicity, which largely limit the therapeutic outcomes. Herein, we report a delivery strategy whereby therapeutic enzymes are encapsulated within a thin zwitterionic polymer shell to form enzyme nanocapsules. The strategy is exemplified by the encapsulation of oxalate oxidase （OxO） for the treatment of hyperoxaluria, because as-synthesized OxO nanocapsules have a prolonged blood circulation half-life and elicit reduced immunogenicity. Our design of enzyme nanocapsules that enable the systemic delivery of therapeutic enzymes can be extended to various biomedical applications.

Study on Plant Regeneration of Wheat Mature Embryos Under Endosperm-Supported Culture

To reveal the suitability of using mature embryos as an explant source in wheat tissue culture, mature embryos from eight common wheat cultivars （Triticum aestivum L. cv.） were cultured with or without endosperm to test their efficiency of callus induction and plant regeneration. When embryos were cultured together with endosperm （endosperm-supported culture, ES）, the percentage of callus induction was significantly lower than that when embryos were cultured in the absence of endosperm （non-endosperm-supported culture, NES）. This pattern was evident in most genotypes, regardless of whether 2 or 8 mg L^-1 2,4-D was added in the NES culture. However, in ES culture, more induced calli were differentiated into distinct green spots and they further developed into plantlets. Thus, more plants were regenerated in ES culture than in the NES treatment. Most of the eight tested genotypes showed a significant difference in callus induction rate and plantlet regeneration in both ES and NES cultures. In addition, the enzymatic activity of oxalate oxidase in the callus of ES culture condition was obviously higher than that in the callus of NES culture condition, suggesting that the activity of oxalate oxidase may be a parameter for selection of calli with potential for plantlet regeneration. These results indicate that wheat mature embryos are valuable explants for highly efficient callus induction and plant regeneration, if proper treatment and medium are used.

Enzymatic Method for Rapid Determination of Oxalic Acid in Bleaching Filtrates from the Pulp and Paper Industry

Bleaching with oxygen-containing agents and recirculation of process streams in the pulp and paper industry has increased the accumulation of oxalic acid and danger for precipitation of calcium oxalate encrusts, scaling. Analysis and control of oxalic acid in bleaching filtrates is therefore becoming increasingly important in the pulp and paper industry. Chromatographic methods, such as IC and HPLC, are generally more time-consuming but are valuable as standard methods for determination of oxalic acid. However, the instrumentation needed is expensive and stationary. In this study, an enzymatic method based on oxalate oxidase and peroxidase was developed to determine oxalic acid in authentic bleaching filtrates using a spectrophotometer. The results showed that bleaching filtrates contain some compounds interfering with the enzymatic method. Pretreatment of the samples with activated charcoal was a successful approach for decreasing problems with interference. By using dilution followed by charcoal treatment, the results obtained from five bleaching filtrates with the colorimetric method correlated very well with those obtained using IC. This study offers a selective, fast and mobile analysis method to determine oxalic acid in bleaching fiRrates from the pulp and paper industry, The convenient enzyme-based method improves the possibilities for control of critical oxalic acid concentrations in closed-loop bleaching streams.