2S albumin gene expression in castor plant (Ricinus communis L.)

In the castor plant (Ricinus communis L.), 2S albumins are highly allergenic seed proteins and are detrimental to the reintroduction of castor as a U.S. crop. Others have shown that the two 2S albumins are encoded by a single gene and processed from a precursor protein in castor. Little is known about the expression pattern of the 2S albumin gene. As part of a genetic approach to eliminating 2S albumin from castor, we investigated the developmental expression of this gene in castor seed. To assess seed developmental 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 analysis indicated that the 2S albumin mRNA is highly abundant in the mid‐phase of seed development. A comparison of 2S albumin genomic DNA and cDNA clones from two castor cultivars indicated that only a single gene is expressed. Protein domain sequence analysis revealed that castor 2S albumin contains the trypsin/α‐amylase inhibitor family domain, suggesting a role for the albumin in insect resistance.