Growth of transgenic canola (Brassica napus cv. Westar) expressing a bacterial 1-aminocyclopropane-1-carboxylate (ACC) deaminase gene on high concentrations of salt Elena Sergeeva 1 , Saleh Shah 2 and Bernard R. Glick 1, * 1 Department of Biology, University of Waterloo, 200 University Avenue West, N2L 3G1, Waterloo, Ontario, Canada 2 Alberta Research Council, Bag 4000T9C 1T4, Vegreville, Alberta, Canada *Author for correspondence: Tel.: 519-888-4567 x5208, Fax: 519-746-0614, E-mail: glick@sciborg.uwaterloo.ca Received 16 May 2005; accepted 28 July 2005 Keywords: ACC deaminase, Brassica napus, canola, ethylene, salt stress, transgenic Summary 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 mea- sured. 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 transfor- mants 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. Abbreviation: ACC – 1-aminocyclopropane-1-carboxylate Introduction One of the major mechanisms that plant growth-pro- moting bacteria use to facilitate the growth of plants involves the enzyme 1-aminocyclopropane-1-carboxyl- ate (ACC) deaminase (Glick 1995; Glick et al. 1998, 1999). Bacteria that are attached to plants (generally to roots, but also to seeds and leaves) and contain the en- zyme ACC deaminase (EC 4.1.99.4) can act as a sink for ACC, the immediate precursor of ethylene in plants. By lowering the concentration of ACC within a plant, the bacteria decrease the extent to which plant ethylene levels become elevated as a consequence of various developmental and environmental signals. Thus, treat- ment of plant seeds or roots with ACC deaminase- containing bacteria lowers the extent of ethylene inhibition of plant seedling root length (Penrose et al. 2001) and helps to protect plants from the deleterious effects of stress ethylene, which is synthesized as a con- sequence of various environmental stresses (Glick et al. 1997) including heavy met als (Burd et al. 1998, 2000), flooding (Grichko & Glick 2001a), phytopathogens (Wang et al. 2000), drought (Mayak et al. 2004a) and high salt (Mayak et al. 2004b). Transgenic plants that have been genetically engineered to express bacterial ACC deaminase are similarly protected from some of the deleterious effects of met als (Grichko et al. 2000; Nie et al. 2002), flooding (Grichko & Glick 2001b) and phytopathogens (Lund et al. 1998; Robison et al. 2001). Worldwide, salinity is one of the most important abi- otic stresses that limits crop growth and productivity. Ion imbalance and hyperosmotic stress in plants caused by high concentrations of salt often lead to oxidative stress conditions for plants. Salinization may be due to natural causes, and is common in the hot and dry regions of the world, or it may be a consequence of inadequate irrigation management practices. In fact, it has been estimated that around 20% of the world’s cultivated lands, and up to half of all irrigated lands are affected by high salinity. Moreover, at the present time there is more arable land being lost through salinity than is gained through the clearing of forests (Frommer et al. 1999). A variety of genetic engineering approaches to the improvement of salt tolerance in plants have been World Journal of Microbiology & Biotechnology (2006) 22:277–282 Ó Springer 2005 DOI 10.1007/s11274-005-9032-1