The identification of cell wall degrading enzymes in Globodera rostochiensis

This thesis describes the identification of cell wall degrading enzymes of the potato cyst nematode Globodera rostochiensis . A robust method using expressed sequence tags (ESTs) was applied to identify new parasitism related enzymes. One of the ESTs revealed the first pectate lyase from a metazoan origin. Another tag shared a strong identity towards a previously determined N-terminal amino acid sequence. Further analysis of corresponding cDNA sequence and the gene revealed two closely related beta-1,4-endoglucanases. Heterologous expression of the pectate lyase and both beta-1,4-endoglucanases showed that they are active enzymes towards their appropriate substrates ( e.g. polygalacturonic acid for the pectate lyase and carboxy methyl cellulose for both beta-1,4-endoglucanases respectively). The application of in situ hybridisation predict that these cell wall degrading enzymes are produced in the subventral oesophageal gland cells. Evidence is provided that nematodes use mixtures of cell wall degrading enzymes in order to penetrate and migrate in the plant root