Reference "Biochemical and genetic analysis of the effects of amylose-extender mutation in rice endosperm"

Reference ID

8195

Title

Biochemical and genetic analysis of the effects of amylose-extender mutation in rice endosperm

Source

Plant physiology, 2001, vol. 127, pp. 459-472

Authors (4)

Nishi-A	Nakamura-Y
Tanaka-N	Satoh-H

Abstract

Biochemical analysis of amylose-extender (ae) mutant of rice (Oryza sativa)
revealed that the mutation in the gene for starch-branching enzyme IIb (BEIIb)
specifically altered the structure of amylopectin in the endosperm by reducing
short chains with degree of polymerization of 17 or less, with the greatest
decrease in chains with degree of polymerization of 8 to 12. The extent of such
change was correlated with the gelatinization properties of the starch granules,
as determined in terms of solubility in urea solution. The ae mutation caused a
dramatic reduction in the activity of BEIIb. The activity of soluble starch
synthase I (SSI) in the ae mutant was significantly lower than in the wild type,
suggesting that the mutation had a pleiotropic effect on the SSI activity. In
contrast, the activities of BEI, BEIIa, ADP-Glc pyrophosphorylase, isoamylase,
isoamylase, pullulanase, and Suc synthase were not affected by the mutation.
Therefore, it is stressed that the function of BEIIb cannot be complemented by
BEIIa and BEI. These results strongly suggest that BEIIb plays a specific role
in the transfer of short chains, which might then be extended by SS to form the
A and B(1) chains of amylopectin cluster in rice endosperm.