The pTiC58 tzs gene promotes high-efficiency root induction by agropine strain 1855 of Agrobacterium rhizogenes.

Root induction on flax (Linum usitatissimum L.) cotyledon explants by Agrobacterium rhizogenes strain 1855 is markedly increased by co-inoculation with disarmed A. tumefaciens strain LBA 4404 containing a plasmid carrying the tzs gene of pTiC58. Most of the roots (estimated to be more than 90%) were transformed. This effect is most likely due to the secretion of trans-zeatin by A. tumefaciens stimulating the division of plant cells making them more receptive to transformation by A. rhizogenes, although other explanations are possible. This observation supports the idea that the tzs gene, although not essential for transformation, may promote transformation. An obvious application for genetic engineering experiments involving transformation by A. rhizogenes, is to include a vir-induced tzs gene in the transformation system to help maximize transformation efficiency.