ENDOGLUCANASE ACTIVITY IN LETTUCE PLANTS COLONIZED WITH THE VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGUS GLOMUS-FASCICULATUM

We studied the production of endoglucanase (EC 3.2.1.4) enzymes during the process of penetration and development of the vesicular-arbuscular (VA) mycorrhizal fungus Glomus fasciculatum in roots of lettuce (Lactuca sativa). Mycorrhizal plants showed more endoglucanase activity than non-mycorrhizal plants. Endoglucanse activity in VA-colonized plants increased at the beginning of the logarithmic stage of fungal development, and subsequently declined. The extracts from external mycelia of G. fasciculatum showed endoglucanase activity. Some of the endoglucanase activities detected in VA-colonized plant roots can be attributed to the VA fungus, since some of the endoglucanase proteins found in the external mycelia of G. fasciculatum and in mycorrhizal root extracts showed the same electrophoretic mobility. However, some of the endoglucanase activities from extracts of mycorrhizal plants had different electrophoretic mobilities than those observed in the external mycelia and in non-mycorrhizal plants. These results suggest that endoglucanases may be involved in the process of colonization of lettuce roots by G. fasciculatum.