Functional and mutated agrocinopine synthase genes on octopine T-DNAs.

Agrocinopine synthase genes have so far been detected only on the Agrobacterium tumefaciens nopaline Ti plasmid pTiC58 and on the A. rhizogenes Ri plasmid pRiA4. The TA region of the octopine/cucumopine (o/c) A. vitis Ti plasmid pTiTm4 strongly resembles the TL DNA of biotype I octopine Ti plasmids. In addition, it carries an intact and functional agrocinopine synthase gene close to its left border. TA/TL sequence comparison shows that the biotype I TL region still carries a 5'-deleted acs gene, strongly indicating that this gene was originally part of the TL region and belongs to the "common DNA" region of octopine and nopaline Ti plasmids. Tm4 and C58C1 (pTiTm4) remove agrocinopine A from the medium indicating that pTiTm4 also carries agrocinopine uptake genes. In spite of this, Tm4 and related strains are resistant against agrocin 84. Two o/c Ti plasmids that are closely related to pTiTm4, pTiHm1, and pTiAB3, have a mutated acs gene; whereas Hm1 can still take up agrocinopine A, AB3 cannot. These results yield new insights in the evolution of octopine, nopaline, and o/c strains.