Expression of the 2S albumin from Bertholletia excelsa in Brassica napus

Abstract

The methionine rich 2S albumin seed storage protein of Bertholletia excelsa has been expressed in seeds of Brassica napus (rapeseed). A chimeric gene driven by the soybean lectin 5' flanking regions was used to produce a fusion protein consisting of the soybean lectin signal peptide and the propeptide of the Brazil nut 2S albumin. Several transgenic plants were studied at the RNA and protein levels; in each case the chimeric gene was expressed and the protein detected at levels ranging from 0.02% to 0.06% of total protein. Transcriptional studies in a particular transgenic plant show that expression of the gene is tissue specific and developmentally regulated during seed maturation. The endogenous napin genes and the introduced gene are regulated differently, with expression of the chimeric gene paralleling that seen when the soybean lectin gene is expressed in other plant species. Western analysis using antibodies to Brazil nut 2S albumins resulted in the detection of a protein whose size is consistent with correct processing of the precursor.