Plant made plastics (PMPs)
Plastics difficult to dispose off and continually accumulating non-degradable wastes have become a significant source of environmental pollution (Shimao, 2001). Biodegradable plastics seem to be a viable alternative to synthetic plastics. The biodegradable materials canundergo decomposition into carbon dioxide, methane, water, inorganic compounds with the help of the enzymatic actions of microorganisms within a specified period of time (Anderson and Dawes, 1990). Polyhydroxyalkanoates (PHAs) are the biodegradable polymers which occur naturally in plants. Plants have been engineered to produce PHAs or PHBs in the various plant cell compartments (John and Keller, 1996; Matsumoto et al., 2009). For the economic feasibility of transgenic plants-derived biodegradable plastics, accumulation of at least 15% of the tissue dry weight is required (Scheller and Conrad, 2005). The expression level of biodegradable plastic-like compounds in plants, have also been targeted to chloroplast (Bohmert et al.,2000; Lossl et al.,2005; Lossl et al.,2003; Nawrath et al.,1994) and expression levels ranging up to 40% of dry weight have been obtained (Bohmert et al., 2000). It was also produced in peroxisomes by using RAVAL residues encoding sequence at the carboxy terminal, accumulating PHBs up to 2% dry weight (Hahnn et al., 1999). There is a need for further improvements in PHB production in plants, aimed at higher accumulation without any side effects in plants.