PERCHLORIC-ACID EXTRACTABLE LOW-MR ALBUMINS SCA AND SAA FROM COTYLEDONS AND SEED AXES OF PEA (PISUM-SATIVUM L)

Using 5% HClO4 extraction and 0.9 N acetic acid/8 M urea/15% polyacrylamide gel electrophoresis two new low-M(r) albumins were revealed in pea (Pisum sativum L) seeds. One of them, termed SCA, predominates among perchloric acid extractable proteins of cotyledons, the other, SAA, in seed axes. Both proteins exhibit similarities in M(r) (approximately 10 kDa), amino acid composition, and antigenic properties. Screening of a world-wide pea collection (approximately 900 accessions) revealed three electrophoretic variants of SCA, which demonstrate a monogenic mode of inheritance. The corresponding gene SCA proved to be linked to r-tl gene complex. All but a few cultivated peas have the same SCA variant. No variants of SAA were observed. Three more perchloric extractable proteins reacting with anti-SCA serum in pea seeds were found. Genes of two of them turned out to be linked to SCA. Proteins resembling SCA and SAA by electrophoretic mobility, antigenic properties, and different concentration in cotyledons and seed axes were found in several other legume species examined. A differential expression of SCA and SAA proteins in seed organs might indicate their function to be related to differences in the physiological state of tissues of a germinating seed. There is apparently a family of several SCA-like proteins that are encoded by a cluster of closely linked genes.