1 Herrera−Estrella et al. identified the promoter sequence of the nopaline synthase (nos) gene. They tested its effectiveness by linking it to the octopine synthase (ocs) structural gene and also to the chloramphenicol acetyltransferase coding gene, which confers resistance to the antibiotic chloramphenicol. In both cases, the nos promoter allowed the transcription of the structural genes in plants. On the contrary, the leghaemoglobin gene under the control of its natural promoter sequence did not express in transformed tobacco cells. The leghaemoglobin gene was known to be expressed only in Rhizobium−induced nitrogen fixing nodules of leguminous plants. Barton et al. cloned the promoter and structural gene of aldehyde dehydrogenase I (Adh−I) from yeast and the promoter and coding sequence of the bacterial gene neomycin phosphotransferase (aph (3′)−II) into an Agrobacterium T−DNA and transformed plants with the constructs. There was no expression of the genes.