COLONIZATION OF TRANSGENIC TOBACCO CONSTITUTIVELY EXPRESSING PATHOGENESIS-RELATED PROTEINS BY THE VESICULAR-ARBUSCULAR MYCORRHIZAL FUNGUS GLOMUS-MOSSEAE

We studied the effect of constitutive expression of pathogenesis-relat ed proteins (PRs) in tobacco plants on vesicular-arbuscular mycorrhiza , Tobacco lines genetically transformed to express various PRs constit utively under the control of the cauliflower mosaic virus 35S promoter of tobacco were examined, Immunoblot analysis and activity measuremen ts demonstrated high levels of expression of the PRs in the root syste ms of the plants, Constitutive expression of the following acidic isof orms of tobacco PRs did not affect the time course or the final level of colonization by the vesicular-arbuscular mycorrhizal fungus Glomus mosseae: PR-1a, PR-3 (=PR-Q), PR-Q', PR-4, and PR-5, Similarly, consti tutive expression of an acidic cucumber chitinase, of a basic tobacco chitinase with and without its vacuolar targeting peptide, of a basic beta-1,3-glucanase, and of combinations of PR-Q and PR-Q' or basic chi tinase and basic beta-1,3-glucanase did not affect colonization by the mycorrhizal fungus, A delay of colonization by G. mosseae was observe d in tobacco plants constitutively expressing the acidic isoform of to bacco PR-2, a protein with beta-1,3-glucanase activity.