Genetic identification of functions of TR-DNA transcripts in octopine crown galls.

Seventeen in vivo and in vitro insertion mutations in the TR-region of the octopine Ti plasmid B6S3 of Agrobacterium tumefaciens were constructed. They include mutations in each of the five TR transcripts. All mutants retained their oncogenic properties and induced tumors with wild-type morphology. Determination of opines in tumors induced by mutant Agrobacterium strains showed that production of mannopine and agropine are TR-linked traits. Two transcripts are necessary for the synthesis of mannopine and a third one for the conversion of mannopine into agropine. None of the mutations prevents the excretion of opines. In addition, none of the five transcripts is essential for transfer and integration of the TR-region.