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Mutations in the Gene Encoding Starch Synthase II Profoundly Alter Amylopectin Structure in Pea Embryos
Josephine Craig, James R. Lloyd, Kim Tomlinson, Lorraine Barber, Anne Edwards, Trevor L. Wang, Cathie Martin, Cliff L. Hedley and Alison M. Smith
The Plant Cell
Vol. 10, No. 3 (Mar., 1998), pp. 413-426
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/3870598
Page Count: 14
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Mutations at the rug5 (rugosus5) locus have been used to elucidate the role of the major soluble isoform of starch synthase II (SSII) in amylopectin synthesis in the developing pea embryo. The SSII gene maps to the rug5 locus, and the gene in one of three rug5 mutant lines has been shown to carry a base pair substitution that introduces a stop codon into the open reading frame. All three mutant alleles cause a dramatic reduction or loss of the SSII protein. The mutations have pleiotropic effects on the activities of other isoforms of starch synthase but apparently not on those of other enzymes of starch synthesis. These mutations result in abnormal starch granule morphology and amylopectin structure. Amylopectin contains fewer chains of intermediate length ( B2 and B3 chains) and more very short and very long chains than does amylopectin from wild-type embryos. The results suggest that SSII may play a specific role in the synthesis of B2 and B3 chains of amylopectin. The extent to which these findings can be extrapolated to other species is discussed.
The Plant Cell © 1998 American Society of Plant Biologists (ASPB)