isolation and characterization novel low-amylose mutants of Pisum sativum L

• Published in: Plant, cell and environment Vol. 18; no. 9; pp. 1019 - 1026
• Main Authors: Denyer, K, Barber, L.M, Burton, R, Hedley, C.L, Hylton, C.M, Johnson, S, Jones, D.A, Marshall, J, Smith, A.M, Tatge, H
• Format: Journal Article
• Language: English
• Published: 01.09.1995
• Subjects: amylose; enzyme activity; granule bound starch synthase; hexosyltransferases; iodine; loci; mutagenesis; mutants; Pisum sativum; recessive genes; seeds; staining; starch; starch granules
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.1995.tb00612.x

Mutants of Pisum sativum L. with seeds containing low-amylose starch were isolated by screening a population derived from chemically mutagenized material. In all of the mutant lines selected, the low-amylose phenotype was caused by a recessive mutation at a single locus designated lam. In embryos of all but one mutant line, the 59kDa granule-bound starch synthase (GBSSI) was absent or greatly reduced in amount. The granule-bound starch synthase activity in developing embryos of the mutants was reduced but not eliminated. These results provide further evidence that amylose synthesis is unique to GBSSI. Other granule-bound isoforms of starch synthase cannot substitute for this protein in amylose synthesis. Examination of iodine-stained starch granules from mutant embryos by light microscopy revealed large, blue-staining cores surrounded by a pale-staining periphery. In this respect, the low-amylose mutants of pea differ from those of other species. The differential staining may indicate that the structure of amylopectin varies between the core and peripheral regions.