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.
Cytosine methylation/de methylation plays pivotal roles in regulating gene expression at a genome-wide level. However, limited reports are available to reveal correlating changes of cytosine methylation and proteomic expression in Brassica napus so far. Therefore, in the present study, global cytosine methylation and proteome were analysed in B. napus after cold treatment by methylation-sensitive amplified polymorphism(MSAP) and two-dimensional protein electrophoresis technology( 2-DE). The results showed that the lowered genome-wide DNA methylation status was revealed after cold treatment, and about 0.88% of discrepancy in DNA methylation was detected between the non-flowering and flowering plants after cold treatment. Moreover, the 52 significantly up-regulated proteins emerged in comparison with the 36 down-regulated proteins, as well as the 14 proteins exclusively detected in the flowering plants. Intriguingly the 8 specifically expressed proteins in the non-flowering plants disappeared in the flowering plants with cold treatment. Therefore, these present data proved that the correlating changes of cytosine methylation and proteomic expression were evidenced under cold treatment in B. napus.
