Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/2009
Publication Date: 5/25/2009
Citation: Whalen, M.C., Kumar, S., Lin, J.T., Hahn, F.M., Cornish, K., Mcmahan, C.M. 2009. Expression of the cytoplasmic mevalonate pathway in chloroplasts. Terpnet 2009.
Technical Abstract: Parthenium argentatum, commonly known as guayule, is a shrub in the Asteraceae family that is native to the southwestern United States and northern Mexico. P. argentatum produces high quality rubber in bark tissue. As an industrial crop that grows in temperate climates, P. argentatum represents a viable source of high quality natural rubber. One strategy for improving crops is through chloroplast engineering. Transformation of chloroplasts allows high-level production of foreign proteins because of the high number of chloroplasts per plant cell and insertions are precise and predictable. Multiple genes can be inserted at once, enhancing the efficiency of metabolic engineering. Importantly, expressing foreign proteins in the chloroplast results in transgene containment in plant species, in which chloroplasts are not transmitted by pollen. As the first step in this strategy, the chloroplast genome of P. argentatum was sequenced and analyzed. The sequence overall is most similar to that of Helianthus annuus. To test our metabolic engineering strategy to enhance delivery of substrate to the rubber synthesizing enzyme, chloroplasts of tobacco were transformed with genes encoding the six enzymes of the cytoplasmic mevalonate pathway. Transplastomic tobacco lines were healthy when grown on medium containing fosmidimycin, indicating successful expression of the pathway. Results of phenotypic analysis of the lines will be presented. Ultimately, improving rubber precursor levels in P. argentatum is expected to enhance rubber production.