Chen, Grace .
Endosperm Morphology and Transcript Profiles of Storage Proteins in Developing Castor Seeds.
Castor oil is the only commercial source of ricinoleic acid and has numerous industrial applications, such as lubricants, coatings, plastics and fungicides. However, castor cultivation and processing generate highly hazardous seed storage proteins, toxin ricin and hyper-allergenic 2S albumins. Its seed meal needs to be heat-denatured after the oil extraction. The health concern and energy cost have thus limited castor domestic production. As a part of a genetic approach to eliminating ricin and 2S albumin from castor, we investigated their gene expression profiles during seed development. To assess seed development age quickly and accurately, we established a set of simple criteria, which included two visual markers, seed coat color and endosperm volume, and defined three phases that encompass the course of castor seed development. Northern analyses showed different temporal expression patterns between ricin and 2S albumin genes, indicating distinctive regulatory mechanisms involved in their mRNA accumulation. During the course of castor seed development, the expression of the 2S albumin was very low in early stages before the endosperm development. The mRNA levels peaked at middle stages when the endosperm underwent rapid growth. Once the endosperm tissue had fully expanded and entered maturation, the mRNA levels decreased. By comparison, no ricin mRNA was detected before the endosperm emerged. A significant amount of ricin mRNA was induced when the endosperm started expansion, and the expression increased aggressively during the rest stages of endosperm development until the maturation. Further characterization of the transcript profiles of 2S albumin from two castor cultivars indicated that only a single gene was expressed. Protein domain analysis revealed that castor 2S albumin contains the trypsin/alpha-amylase inhibitor pfam domain, suggesting a role for the albumin in insect resistance.
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1 - U.S. Department of Agriculture, Agricultural Research Service, Western Regional Research Center, 800 Buchanan St., Albany, California, 94710, USA
Presentation Type: Oral Paper
Date: Monday, August 15th, 2005
Time: 9:30 AM