Submitted to: Proceedings JOCS/AOCS World Congress
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2007
Publication Date: 5/2/2007
Citation: Chen, G.Q., Mckeon, T.A., Lin, J.T. 2007. Developing a safe source of castor oil. Proceedings JOCS/AOCS World Congress.
Technical Abstract: Castor bean (Ricinus communis L.) is an important oilseed crop with significant industrial value. However, the production of castor oil is hampered by the presence of the toxin ricin and hyper-allergenic 2S albumins in its seed. We are thus investigating the possibility of developing a safe source for castor oil production by two different approaches: blocking gene expression of the ricin and 2S albumins in castor seed; and engineering a temperate oilseed crop to produce castor oil. In or to understand how castor oil synthesis is regulated, we conducted a series of castor seed developmental studies including endosperm morphogenesis, reserve biosynthesis and gene expression. The entire course of seed development can be divided into eight stages, which are recognizable by distinct seed coat color and volume of cellular endosperm. Synthesis of ricin, 2S albumins and oil occure during cellular endosperm development. Concomitantly, we observed increased transcript levels of 14 genes involved in synthesis of ricin, 2S albumin and oil, but with various temporal patterns and different maximal indictions ranging from 2 fold to 43,000 fold. The results indicate that gene transcription exerts a primary control in castor reserve biosynthesis. Based on the temporal pattern and level of gene expression, we classified these genes into five groups. These transcription-profiling data provide not only the initial information on promoter activity for each gene, but also a first glimpse of the global patterns of gene expression and regulation, which are critical to metabolic engineering of transgenic oilseeds. Since all these studies are illustrated based on a well-defined time course, the results also provide integrative information for inderstanding the relationships among morphogenesis, reserve biosynthesis and gene expression during castor seed development.