Opines in crown gall tumours induced by biotype 3 isolates of Agrobacterium tumefaciens.
Pathogenic properties and opine markers of biotype 3 (grapevine) isolates of A. tumefaciens were compared with those of biotypes 1 and 2. Compared with biotypes 1 and 2, grapevine isolates induced only small tumours on Kalanchoe daigremontiana stems but produced large organogenic galls on decapitated shoot tips. Grapevine agrobacteria were classified according to their opine catabolic properties and the type of opine they induced in K. tubiflora and grapevine tumours. Crown gall tissues obtained after infection with octopine-utilizing grapevine isolates contained octopine in very large amounts compared with biotype 1 tumours. A similar quantitative difference was not observed when nopaline production of tumours incited by biotypes 1 and 2 and by grapevine isolates was examined. Tumours formed by a third class of grapevine isolates synthesized a novel opine, for which the trivial name vitopine is proposed. Octopine, nopaline, agropine and vitopine were also detected in healthy tissues of plants infected with the appropriate A. isolates, indicating that these opines can selectively promote the colonization of the whole plant by agrobacteria. Biotype 3 octopine isolates induced octopine synthesis at the infection sites of a crown gall-resistant grapevine hybrid, showing that pathogenic agrobacteria can transform plants without tumour formation.