IN VIVO FUNCTIONAL ASSAY OF WUS ORTHOLOG IN TOBACCO

We have isolated a tobacco cDNA encoding a protein (309 amino acid) homologous to WUSCHEL (WUS) from Arabidopsis. The putative amino acid sequence showed only 38% identity with WUS in whole sequence but 84%, 100%, and 87% identity with the homeodomains, WUS box and repressor domains in the corresponding regions respectively. The sequence was introduced into tobacco genome under the transcriptional control of ß-estradiol-inducible expression system (XVE system) via Agrobacterium-mediated transformation. The resulting transgenic plants were matured to harvest their seeds. When the transgenic seedlings were replaced on the medium with the inducer, bulbing was observed in the root tip region followed by shoot formation. This observation was similar to our previous result using tobacco seedlings transgenic for WUS from Arabidopsis, under the control of XVE system. We conclude that the cDNA is probably an ortholog for WUS in tobacco and we referred to it as NtWUS. Our observation may provide an alternative method for estimating the function of WUS and related gene in vivo.