INDUCTION OF NEW CHITINASE ISOFORMS IN TOMATO ROOTS DURING INTERACTIONS WITH GLOMUS-MOSSEAE AND OR PHYTOPHTHORA-NICOTIANAE VAR PARASITICA/

Chitinase activities were investigated by native and denaturing SDS-PA GE in tomato roots during symbiosis with the arbuscular mycorrhizal (A M) fungus Glomus mosseae, in a pathogenic interaction with Phytophthor a nicotianae var parasitica and in pathogen-infected roots pre-inocula ted with G mosseae for 2 weeks. Several native acidic chitinase isofor ms were found in control roots. One additional isoform was detected in G mosseae-colonized roots, while a different one was found in pathoge n-infected roots, as well as stronger expression of constitutive isofo rms. All the chitinase isoforms were found in tomato roots pre-inocula ted with G mosseae and post-infected with the pathogen. Four basic iso forms were present in all extracts, but they only showed enhanced acti vities in pathogen-infected roots. Chitinases from AM roots renatured more quickly and easily than those from non-mycorrhizal roots, after d enaturing under non-reducing conditions, even when mycorrhizal plants were post-infected with the pathogen.