CHROMOSOMAL AND CYTOLOGICAL LOCALIZATION OF THREE PEROXIDASES INDUCED BY CEREAL CYST NEMATODE IN WHEAT

In a previous work the characterization and the alignment of twenty peroxidase genes together with phylogenetic clustering with peroxidases from other plant species showed that these enzymes fall into seven different groups (designated TaPrx108 to TaPrx114). These represent peroxidases secreted to the apoplast by a putative N-terminal peptide signal. Three groups of peroxidase genes (TaPrx111, TaPrx112 and TaPrx113) were found to be greatly induced by the cereal cyst nematode Heterodera avenae in the H-93-8 resistant wheat line. In situ hybridization analyses of genes belonging to these groups revealed a strong signal of these peroxidases in cells close to the vascular cylinder and parenchyma vascular cells when challenged by nematodes. In particular, parenchyma cells, where the nematode starts its feeding, were hyper-reactive to some probes belonging to TaPrx112 and TaPrx113 groups. These findings suggest that wheat apoplastic peroxidases may have a role in the defence response. TaPrx111-A, TaPrx112-D and TaPrx113-F peroxidases were characterized and their sequences were used to design specific pair primers from each group. Chromosomal analyses by PCR marker mapping and using Sears's aneuploid wheat lines cv. 'Chinese Spring' indicated that these peroxidases are located on the short arm of the chromosome 2B and that they may be linked each other.