Evidence for a cellular gene with potential oncogenic activity in plants.

During tumor inception in crown gall disease, a portion of the tumor-inducing (Ti) plasmid, the transferred DNA (T-DNA), is integrated into the genome of the plant cell. Autonomous growth of the transformants requires expression of genes in the tmr and tms regions of the T-DNA, which code for enzymes concerned with biosynthesis of the plant growth hormones cytokinin and auxin, respectively. We show that a mutation of the Habituated leaf gene, Hl, of tobacco can compensate for a defective tmr locus in expression of the tumor phenotype. This provides evidence that a specific host-cell gene has an oncogenic function similar to tmr in the T-DNA.