Expression of poly-3-(R)-hydroxyalkanoate (PHA) polymerase and acyl-CoA-transacylase in plastids of transgenic potato leads to the synthesis of a hydrophobic polymer, presumably medium-chain-length PHAs

Abstract

Medium-chain-length poly-3-(R)-hydroxyalkanoates (mcl-PHAs) belong to the group of microbial polyesters. The minimum gene-set for the accumulation of mcl-PHAs from de novo fatty acid biosynthesis has been identified in prokaryotes [B. Rehm et al. (1998) J. Biol Chem 273:24044-24051] as consisting of the Pha-C1 polymerase and the ACP-CoA-transacylase. In this paper, the synthesis of mcl-PHAs has been attempted in transgenic potato (Solanum tuberosum L.) using the same set of genes that were introduced into potato by particle bombardment. Polymer contents of transgenic lines were analysed by gas chromatography and by a new simple method employing a size-exclusion filter column. The expression of the Pha-C1 polymerase and the ACP-CoA-transacylase in the plastids of transgenic potato led to the synthesis of a hydrophobic polymer composed of mcl-hydroxy-fatty acids with carbon chain lengths ranging from C-6 to C-12 in leaves of the selected transgenic lines. We strongly suggest that the polymer observed consists of mcl-PHAs and that this report establishes for the first time a possible route for the production of mcl-PHAs from de novo fatty acid biosynthesis in plants.

Particle bombardment and the genetic enhancement of crops: myths and realities

“…The results were interesting because, as well as proving that transformation and subsequent transgene expression were possible using minimal cassettes, the resulting transgenic plants showed much simpler integration patterns and lower transgene copy numbers than plants transformed with equivalent constructs in their source plasmids. These results have been confirmed in subsequent studies with agronomically useful genes and multiple cassettes, as discussed in the next section (Breitler et al 2002;Loc et al 2002;Romano et al 2003a;Romano et al 2005).…”

“…For potato transformation, even non-embryogenic tissues (i.e. nodes, leaves and microtubers) have been shown to be suitable targets for both transient expression and stable transformation by particle bombardment in different cultivars (Romano et al , 2003bRomano et al 2005). This indicates that both undifferentiated cells and well-differentiated, organized tissues are amenable to this method of transformation.…”

Employing a composite gene-flow index to numerically quantify a crop’s potential for gene flow: an Irish perspective

“…However, the potential admixture of conventional and GM crop derived material that has been developed for non-food use could present both economic and social consequences. Specifically, this relates to the use of traditional crops for non-food use; for example the production of therapeutics (Thanavala et al, 2005) and biodegradable plastics (Romano et al, 2005). For Ireland, the cultivation of these second and third generation GM crops could provide the tillage industry with the level of diversification it seeks in order to address current market pressures.…”

Production of renewable polymers from crop plants

“…In addition to the biotechnological aspects, synthesis of mclPHA in plants has been used as a valuable tool to study carbon flux through the b-oxidation cycle, as PHA accumulation reflects the carbon flux through the b-oxidation pathway, while monomer composition provides information on the type of fatty acids entering the cycle and how they are degraded (Poirier, 2002). Producing mclPHAs containing longer-chain monomers in plastids using conversion of the fatty acid biosynthetic intermediate 3-hydroxyacyl-ACP into 3-hydroxyacyl-CoA via expression of a bacterial 3-hydroxyacyl-ACPCoA transacylase led to the accumulation of only very low amounts of mclPHA (below 0.03% dry weight) in potato leaves (Romano et al, 2005).…”