Investigation of the effect of rolC and trolC genes on germination and growth parameters of transgenic tobacco (Nicotiana tabacum) seedlings

Agrobacterium rhizogenes is a soil-borne, gram negative bacterium which induces hariy root disease in plants. A DNA sequence in the bacterial plasmid called T-DNA (transferred DNA) is transferred in to the plant genome upon infection. T-DNA carries the rooting-locus (rol) genes: rolA, rolB and rolC. Somme plants also contain, naturally, the homologues of rol genes. In this study, the effects of bacterial rolC gene and its homologous in tobacco, trolC, was evaluated in transgenic plants in a completely randomized design experiment with 3 replications. The expression of rolC and trolC genes in transgenic tobacco seedlings was under the control of dexamethasone inducible promoter. Different concentrations of dexamethasone (0, 1, 3, 10 and 30 µM) were used in order to induce the expression of transgenes. Our results showed that the presence of only very low quantity of dexamethasone (1µM) in the culture medium induces the expression of genes and affect significantly the growth of seedlings. Phenotypically, the length of seedlings was shorter in both transgenic plants than control and the roots of transgenic seedlings were twisted and the leaves were smaller and pale green. Since these characteristics are present in both transgenic seedlings, we can conclude that the bacterial rolC gene has preserved its ancestral function after insertion into the plant genome during evolution.