Copyright (c) 2009 All rights reserved. http://works.bepress.com/david_leach Recent documents in David N Leach en-us Wed, 28 Oct 2009 23:19:50 PDT 3600 http://works.bepress.com/david_leach/69 http://works.bepress.com/david_leach/69 Tue, 27 Oct 2009 22:53:33 PDT Dale A. Shelton http://works.bepress.com/david_leach/70 http://works.bepress.com/david_leach/70 Tue, 27 Oct 2009 22:53:33 PDT Dale A. Shelton http://works.bepress.com/david_leach/71 http://works.bepress.com/david_leach/71 Tue, 27 Oct 2009 22:53:33 PDT Dale A. Shelton http://works.bepress.com/david_leach/67 http://works.bepress.com/david_leach/67 Tue, 27 Oct 2009 22:53:32 PDT Melaleuca alternifolia is an evergreen, Australian native tree species commonly referred to as Tea Tree. It is the major source of Australian tea tree oil, an economically important product with anti-microbial properties. The anti-microbial properties of the oil are primarily attributed to the monoterpene terpinen-4-ol. Terpinen-4-ol is produced by the skeletal rearrangement of sabinene hydrates both in vivo and in vitro. The oil also contains significant levels of the monoterpenes 1,8 cineole, terpinolene and a- and g- terpinene along with some sesquiterpenes. Amino acid sequence comparison of other terpene synthases isolated from a diverse range of plants revealed regions of high or absolute conservation. Degenerate primers were designed to these regions and used to generate oligonucleotide probes for monoterpene synthases. These probes were then used to screen a cDNA library derived from M. alternifolia flush growth, the primary site of monoterpene biosynthesis. As a parallel approach to elucidating the biochemistry of terpene biosynthesis in M. alternifolia, cell free extracts with sabinene hydrate synthase activity have also been generated. Dale A. Shelton http://works.bepress.com/david_leach/68 http://works.bepress.com/david_leach/68 Tue, 27 Oct 2009 22:53:32 PDT L Slade Lee http://works.bepress.com/david_leach/65 http://works.bepress.com/david_leach/65 Tue, 20 Oct 2009 22:51:25 PDT Shahid Chohan http://works.bepress.com/david_leach/66 http://works.bepress.com/david_leach/66 Tue, 20 Oct 2009 22:51:25 PDT Robert J. Henry http://works.bepress.com/david_leach/64 http://works.bepress.com/david_leach/64 Wed, 30 Sep 2009 19:04:09 PDT Melaleuca alternifolia, is a commercially important, Australian native tree commercially harvested for its monoterpene-rich essential oil. A random selection of 454 clones from a cDNA library derived from flush growth were sequenced and analysed. Amongst five most abundant sequences abundant sequences were sequences that encoded Rubisco and photosystem II, as expected. The remaining three abundant sequences included a GATA transcription factor homolog, a sequence with low homology to a hypothetical protein from a plastid genome of Evening Primrose (Oenothera elata) and a short sequence with no homology. These latter three pose interesting targets for functional genomic studies as their function is unknown and their relative high abundance infer a pivotal role in young tissue of M. alternifolia. Three ESTs involved in terpene biosynthesis were isolated, a cycloartenol synthase-like protein, a limonene synthase-like protein, farnesyl pyrophosphate synthase, of which only the latter two are involved in the production of the valuable essential oils. However, five ESTs were isolated for phenylpropanoid biosynthesis, excluding those that are committed to lignin biosynthesis. Other secondary metabolite-related ESTs included genes for lycopene and the plant growth regulator biosynthesis as well as numerous cytochrome p450's of unknown function. A total of 5% of ESTs isolated in this study are involved directly with secondary metabolite production. This study illustrates the utility of ESTs as a new method for bio-prospecting for secondary metabolites in simple plant tissues. Dale A. Shelton http://works.bepress.com/david_leach/63 http://works.bepress.com/david_leach/63 Tue, 25 Aug 2009 21:50:16 PDT Dale Shelton http://works.bepress.com/david_leach/62 http://works.bepress.com/david_leach/62 Sun, 19 Jul 2009 19:25:33 PDT The composition and yield of oil in 615 trees representing the natural populations of Melaleuca alternifolia, or tea tree, was investigated. A sixth distinct oil chemotype was identified. Of the six chemotypes, one chemotype is dominated by terpinen-4-ol, one by 1,8-cineole, one by terpinolene and the remaining three chemotypes are all dominated by 1,8-cineole and differ in either terpinen-4-ol or terpinolene content. Whilst most chemotypes are present throughout the distribution range, a definite correspondence of oil types with geographic location was found. Terpinen-4-ol types predominate in and around the Bungawalbin basin in the Casino area of northern New South Wales (NSW), high 1,8-cineole types predominate toward the southern end of the distribution around Grafton and terpinolene types predominate in southern Queensland. Preliminary formulae have been developed to allow comparisons of oil data obtained by steam distillation with a static headspace gas chromatography method. Laura E. Homer