Genetic control and biochemical properties of some high molecular weight albumins in bread wheat

Abstract

Analysis of aneuploid stocks of Chinese Spring wheat showed that some of the seed protein bands separated by two-step SDS—PAGE ( M r 65, 63, 60 and 45k) are controlled by genes on the chromosome arms 4DL, 4AL, 5AL and 5DL. The extractability characteristics of these bands indicated that they are albumins. One-dimensional SDS—PAGE analysis of protein fractions separated by size exclusion HPLC showed that these albumin bands are part of the polymeric protein fraction in bread wheat. Fractionation of total seed-proteins by diagonal electrophoresis (unreduced x reduced) revealed that the high molecular weight albumin bands occur in both polymeric (disulphide-linked aggregates) and monomeric forms in their native state. These proteins were rapidly degraded during seed germination like the storage proteins of wheat. They were found not to be present in the protein bodies from developing wheat endosperm, however. Subsequent analysis of these albumins using immunoblotting revealed that the bands controlled by chromosome arm 4DL, 4AL and 5AL are beta-amylases of wheat grain, and are probably encoded at the β- Amy-1 loci on these arms. A limited amount of allelic variation in these bands was observed by two-step SDS—PAGE of different bread wheat cultivars.