Oil biosynthesis

FUNCTIONAL GENOMICS APPROACHES TO UNRAVEL ESSENTIAL OIL BIOSYNTHESIS... 

The peppermint oil gland secretory cell cDNA library has proven to provide a highly enriched source of candidate genes involved in essential oil biosynthesis. A functional genomics approach has successfully been employed to clone genes involved in the mevalonate-independent pathway of isoprenoid biosynthesis and in the peppermint-specific steps producing (-)-menthol and (-)-menthone. The optimization of LC-MS technology to profile phosphoiylated carbohydrates and... 

LANGE, B.M., WILDUNG, M.R., STAUBER, E.J., SANCHEZ, C., POUCHNIK, D., CROTEAU, R., Probing essential oil biosynthesis by functional evaluation of expressed sequence tags from mint glandular trichomes, Proc. Natl. Acad. Sci. USA, 2000, 97, 2934-2939. 

Functional Genomics Approaches to Unravel Essential Oil Biosynthesis.145... 

Mahmoud SS, Croteau R, Menthofuran regulates essential oil biosynthesis in peppermint by controlling a downstream monoterpene reductase, Proc Natl Acad Set USA 100 14481-14486, 2003. 

There appear to be species-based differences in the relative contributions of type 1 versus type 2 DGAT to TAG accumulation during seed development. DGAT2 has been shown to play a major role in TAG accumulation in the seeds of the tung tree ( Vernicia fordii) and castor bean (Ricinus communis), in which the enzyme is involved in the incorporation of unusual fatty acyl moieties (Kroon et al. 2006, Shockey et al. 2006). The in vivo contribution of DGAT2 to oil biosynthesis in developing seeds of B. napus, however, remains to be elucidated (Gaboon et al. 2007). 

Andre, C., J.E. Froehlich, M.R. Moll, and C. Benning. 2007. A heteromeric plastidic pyruvate kinase complex involved in seed oil biosynthesis in Arabidopsis. Plant Cell 19 2006-2022. 

Wang, H., I. Guo, K.N. Lambert, and Y. Lin. 2007a. Developmental control of Arabidopsis seed oil biosynthesis. Planta 226 773-783. 

McKeon, T., S.-T. Kang, C. Turner, X. He, G. Chen, and J.-T. Lin. 2006. Enzymatic synthesis of intermediates in castor oil biosynthesis. 97th AOCS Aimnal Meeting and Expo, p. 15. 

Modification of oil composition remains a major interest of plant breeders, both traditional and molecnlar. The oil represents a major component present in the seed and is easily isolated. As a result of research on biochemistry and genetics of oil biosynthesis, there is considerable backgronnd information that elucidates the process of triacylglycerol (TAG) (oil) biosynthesis. Oils have both food and indnstrial uses, and... 

Since the hydroxylase gene alone was not sufficient to elicit high levels of hydroxy fatty acid production, it seemed that there must be other enzymes required to achieve high ricinoleate levels in oil [14]. Based on intermediates that accumulated during in vitro castor oil biosynthesis carried out by castor seed microsomes, several enzymatic steps that appear to be important for high ricinoleate levels have been identified [14], The pathway derived from this research is shown in Figure 6.3. 

Further studies [15] indicated that ricinoleate is preferentially incorporated into TAG by a factor of 6 over oleate, leading us to identify the final step in oil biosynthesis (Figure 6.4) as a key step in maintaining high ricinoleate content while... 

Indeed, as a result of our cloning of the DGAT from developing castor seed, we were able to demonstrate that the activity and protein level of the cloned DGAT is closely correlated with the onset of oil biosynthesis in the seed [17]. Moreover, the... 

In this study, we identified and quantified 61 molecular species of acylglycerols, 36 PC and 35 PE in castor microsomal incubations of six [ CJFA individually. The results show the following (i) 2-oleoyl-PC is actively formed as the immediate substrate of oleoyl-12-hydroxylase, a key enzyme for castor oil biosynthesis (ii) 2-ricinoleoyl-PC is formed mainly by the hydroxylation of 2-oleoyl-PC, not from the incorporation of ricinoleate into 2-ricinoleoyl-PC and (iii) 2-oleoyl-PE is not actively formed for the biosynthesis of castor oil. 

We have elucidated the biochemistry of castor oil biosynthesis, an essential step in generating effective transgenic sources of a high ricinoleate oil. Because this aspect of our research has been described recently (6), and is discussed further in this volume (7), this paper will focus mainly on our other fatty acid of interest, cw-vaccenate. 

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