Vicilins
Eight vicilin isoforms are encoded by genes in the camelina genome (Supplementary Table S1), of which six were identified in 13 2DE spots from the cruciferin-enriched fraction (Supplementary Table S2). These six isoforms accounted for 0.2-10.2% of the total protein in the 13 spots. CsVic1B-1-G2 and CsVic2-1-G2 were not found in the cruciferin-enriched, napin-enriched or oil body protein fractions (Supplementary Tables S2-S5). The most prevalent vicilin isoform was CsVic1A-1-G1 (Csa19g031870, 11 spots), followed by CsVic1A-1-G2 (Csa01g025880, 7 spots), CsVic1B-1-G3 (Csa15g039300, 7 spots) and Csa05g038120 (6 spots). Vicilin is a 7S trimeric globulin found mainly in legumes (Shewry et al., 1995). Similar to cruciferin, vicilin is a cupin super-family protein containing a characteristic ‘jelly-roll’ β-barrel domain (Shewry et al., 1995); however, it forms a trimeric quaternary structure as the protomer is not processed and lacks the internal S-S bond present in cruciferin that is involved in structural changes associated with hexamer assembly. Mature trimeric vicilins have molecular weights of ~ 150-200 kDa (Shewry, 1998). Camelina vicilin protomers ranged from 462-535 amino acids (Supplementary Figure S2) with molecular weights between 52.0 kDa and 58.5 kDa and migrate with cruciferin subunits in SDS-PAGE gels under non-reducing conditions, but are separable under reducing conditions. The ~69 kDa and ~53 kDa polypeptides observed in camelina meal under reducing conditions (Figure 3A) may be vicilins. Some vicilins, such as that from pea (Casey et al., 1986), are proteolytically-processed yielding smaller polypeptides. If this is also the case for camelina vicilins, they might migrate with the free α- and β-chains of cruciferin (Figure 3B). Delseny and Raynal (1999) and Shewry and Casey (1999) reported two genes, AtPAP85 (Q9LUJ7) and AtVCL22 (Q9SK09), that encode 7S proteins in A. thaliana that were highly similar to pea vicilin and related legume 7S proteins.