The oilseed plant castor bean (Ricinus communis) is a member of
oilseed plant castor bean (Ricinus communis) is a member of
the family Euphorbiaceae. Cassava (Manihot esculenta), rubber
tree (Hevea brasiliensis), ornamental poinsettias (Euphorbia
pulcherrima), and the invasive weed leafy spurge (Euphorbia
esula) are other important members of this family that includes
nearly 250 genera comprising 6,300 species.
Castor oil is extracted from R. communis seeds and has multiple
applications. Castor bean seed triacylglycerols (TAG) contain 90%
ricinoleate (12-hydroxy-oleate) and is the only commercial source of
hydroxy-fatty acid, an unusual fatty acid. The hydroxy group has
special chemical and physical properties that make castor oil a vital
industrial raw material for numerous products, including high quality
lubricants, paints, coatings, plastics, soaps, medications for skin
affections and cosmetics. Castor oil can be used as lubricity
additive to replace sulfur-based lubricity components in petroleum
diesel helping to reduce sulfur emissions.
bean seeds also contain high concentrations of a type 2
ribosome-inactivating enzyme, ricin, which is one of the deadliest
natural poisons. Therefore, there is also an interest in castor bean
from the bio-defense point of view. The world annual castor oil
production in 2004-5 was around 0.5 million tons but, due to the
presence of ricin, castor bean is not grown commercially in the U.S.
Rather, the U.S. is amongst the world largest importers of castor oil
and its derivatives. Deeper understanding of the castor bean biology
will allow improvements in castor oil production without the problem
of ricin, either by engineering castor bean or other oilseed plants.
We have sequenced and assembled a 4X draft of the ~400 Mbp castor
bean genome using a whole genome shotgun strategy. In addition,
~50,000 ESTs from different tissues have been produced to help gene
discovery and annotation. Preliminary comparisons between castor bean
genes and ESTs from other available Euphorbiaceae species, showed
that cassava shares the highest sequence similarity with castor bean.
With the on-going DOE-JGI cassava genome sequencing project, castor
bean and cassava will constitute a valuable comparative genomics
project is funded by the NIAID-NIH, through the Microbial Genome
Sequencing Center at TIGR (http://www.tigr.org/msc).