Agropine in "null-type" crown gall tumors: Evidence for generality of the opine concept.

Agrobacterium Ti (tumor-inducing) plasmids, the causative agents of crown gall disease, fall into four genetic groups based on the patterns of octopine and nopaline synthesis (by crown gall tumors) and catabolism (by Agrobacterium tumefaciens) for which they are responsible. Two classes of Ti plasmids induce tumors that synthesize neither octopine nor nopaline. The existence of these Ti plasmids challenged the view that opines such as octopine and nopaline play a central role in crown gall biology. We now report the occurrence of an opine in tumors induced by one of these classes of Ti plasmids, the "null-type" plasmids typified by pTi Bo542. The opine was purified by biological enrichment based on its utilization by bacteria containing pTi Bo542 but not by bacteria lacking a Ti plasmid. The mass spectrum and biological properties of this opine are identical to those of agropine, an opine recently discovered in octopine-type tumors. We propose that null-type Ti plasmids now be named for their signal opine, agropine-type Ti plasmids.