Growth of transgenic canola (Brassica napus cv. Westar) expressing a bacterial 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene on high concentrations of salt

Canola, Brassica napus cv. Westar, was transformed to express a bacterial 1-aminocyclopropane-1-carboxylate (ACC) deaminase (EC 4.1.99.4) gene under the transcriptional control of (a) the constitutive and strong 35S promoter from cauliflower mosaic virus, (b) the root-specific promoter of the rolD gene within the T-DNA from the Ri plasmid of Agrobacterium rhizogenes, and (c) the promoter for the pathogenesis-related prb-1b gene from tobacco. Following the growth of transformed and non-transformed canola plants in the presence of 0-200 mM NaCl, the fresh and dry weights of plants, leaf protein concentration, and leaf chlorophyll contents were measured. The data suggest that the presence of ACC deaminase provides the transgenic canola lines with tolerance to the inhibitory effects of salt stress, compared to the non-transformed canola plants, with the rolD transformants being the most effective. The improved salt tolerance of these transgenic plants is likely the consequence of the decreased synthesis of stress ethylene. This data is consistent with previous studies with transgenic tomato plants expressing bacterial ACC deaminase which showed that lowering ethylene levels partially protected plants against growth inhibition by metals, phytopathogens and flooding.