ENZYMES AND PROTEINS INVOLVED IN THE RESISTANCE TO SCLEROTINIA SCLEROTIORUM IN OILSEED RAPE
SY LIU1, BW ZHOU1, QF XIONG2 and HS LI2
1Oil Crops Research Institute, Chinese Academy of Agricultural Science, Wuhan 430062 China; 2Huazhong Agricultural University, Wuhan 430070, China
Background and objectives
Results and conclusions
Experiments with rape seedlings fed with 14C-oxalate through roots for 4 h showed significant uptake of the toxin. The autoradiographic profile of seedlings showed that in resistant varieties radioactivity was confined to major veins of leaves and stems, and that the activity in the interveinal tissue was low. In contrast, in susceptible varieties radioactivity was distributed rather uniformly throughout the seedlings. The metabolism of OA was examined.
New protein bands were found by SDS-PAGE 72 h after seedlings were inoculated with the fungus and OA. A 27.5-kDa protein was consistently induced by the fungus, and a 54.8-kDa protein was induced by OA. Two to five bands disappeared in susceptible varieties after inoculation. The 54.8-kDa protein was prepared to immunize rabbits and the antiserum was collected. Double-agar diffusion testing proved that the 54.8-kDa protein was not peroxidase from horseradish or rape leaves. Whether these new proteins are OAO or other functioning enzymes needs to be ascertained.
In conclusion, the studies showed that the following factors contributed toward higher resistance in resistant varieties than susceptible ones: the limited uptake and transport of OA, high rate of metabolism of OA by leaves and more increase of PO, OAO and SOD activity induced by OA or the fungus. The oxidation of H2C2O4 promoted by oxidation of polyphenols in which the first reaction product, H2O2, served as a substrate of the second reaction might play a role in the process of resistance.