Transgenic Arabidopsis plants can accumulate polyhydroxybutyrate to up to 4% of their fresh weight

Transgenic Arabidopsis thaliana (L.) Heynh. plants expressing the three enz ymes encoding the biosynthetic route to polyhydroxybutyrate (PHB) are descr ibed, These giants accumulated more than 4% of their fresh weight (approxim ate to 40 % of their dry weight) in the form of PHB in leaf chloroplasts. T hese very high producers were obtained and identified following a novel str ategy consisting of a rapid GC-MS analysis of a large number of transgenic Arabidopsis plants generated using a triple construct, thus allowing the pa rallel transfer of all three genes necessary for PHB synthesis in a single transformation event. The level of PHB produced was 4-fold greater than pre viously published values, thus demonstrating the large potential of plants to produce this renewable resource. However, the high levels of the polymer produced had severe effects on both plant development and metabolism. Stun ted growth and a loss of fertility were observed in the high-producing line s, Analysis of the metabolite composition of these lilies using a CC-MS met hod that we have newly developed showed that the accumulation of high level s of PHB was not accompanied by an appreciable change in either the composi tion or the amount of fatty acids. Substantial changes were, however, obser ved in the levels of various organic acids, amino acids, sugars and sugar a lcohols.