Vol. 20 >B. Research Notes>IV. Genetics of physiological traits and others |
28. | Isolation and characterization of a rice mutant with enhanced amylose content in endosperm derived from a low amylose variety "Snow pearl" |
SUZUKI, Y.1, H.-Y. HIRANO2, Y. SANO3, U. MATSUKURA1, S. KAWASAKI4, M. CHONO1, S. NAKAMURA1 and H. SATO1 1) National Institute of Crop Science, Kannondai, Tsukuba, Ibaraki 305-8518, Japan. 2) Graduate School of Agricultural and Life Sciences, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. 3) Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kita-ku, Sapporo 060-8589, Japan. 4) National Institute of Agrobiological Sciences, Kannondai, Tsukuba, Ibaraki 305-8602, Japan. |
The amylose content of endosperm starch is an important characteristic
of rice in determining eating and cooking quality. The amylose content
is genetically controlled by a major gene, the Waxy (Wx) gene.
In addition, amylose content is also affected by several modifying genes
and environmental factors such as temperature. The Wx gene encodes
the granule-bound starch synthase that is responsible for amylose synthesis
in the endosperm. Rice strains having the Wxb gene contain
15-20% amylose in contrast to rice strains having the Wxa
gene contain 20-25% amylose (Sano 1984). The du loci modify amylose
content by controlling expression of the Wxb gene and
mutations at the du loci cause a reduction in amylose content (Okuno
et al 1983, Hirano 1993). Although the amylose-extender
(ae) mutant shows increasing levels of apparent amylose content,
this increase in amylose content is caused by the altered amylopectin
structure and the ae mutation is found in the gene for starch-branching
enzyme IIb (Nishi et al. 2001). While there are many mutants concerning
starch composition, there is no report about the gene, of which mutation
gives rise to elevation of amylose content in the endosperm. In this paper,
we describe the isolation and characterization of a rice mutant with enhanced
amylose content in the endosperm that does not affect the amylopectin
structure. SP14 was increased by the ae locus, the amylopectin
chain length distribution in rice endosperm was analyzed by high performance
anion exchange chromatography with a pulsed amperometric detector. Because
the chain length distribution of amylopectin were almost the same between
the two strains maturated at both temperatures (data not shown), the mutation
in SP14 would not be the ae mutation reported previously (Nishi
et al. 2001), but a new mutation that enhances amylose content
in rice endosperm. Though it should be also noted whether SP14 is derived
from "Snow pearl" or not, our preliminary data on the nucleotide
sequences in Wx gene indicates SP14 is derived from Snow pearl.
Thus, this mutant should be useful in breeding programs designed to produce
rice of an abundant quality and in understanding genetic and molecular
mechanisms for amylose synthesis. |
Vol. 20 >B. Research Notes>IV. Genetics of physiological traits and others |