2008 Volume 58 Issue 3 Pages 209-215
The Wxb gene, one of the alleles at the rice waxy locus, responds to environmental temperatures during seed development and, as a result, the amylose content fluctuates and affects rice quality. Seeds of a low-amylose variety ‘Snow Pearl’ could be visibly distinguished depending on whether they matured in warm or cool temperatures; based on this, we isolated a mutant candidate, namely, the enhanced amylose content (ENA) mutant, which showed enhanced amylose content in the endosperm. The amylose contents of ENA mutants that matured at 20°C and 26°C were 6–7% higher than those of Snow Pearl. As the chain length distributions of amylopectin were almost identical between ENA and Snow Pearl, the mutation was not the amylose-extender mutation, but a new mutation that enhanced amylose content in the rice endosperm. Furthermore, ENA and Snow Pearl had a single nucleotide polymorphism on the third exon of the Wx gene and a single base change at the 5′ splice junction of the first intron specific to the Wxb gene. Genetic analysis revealed that enhanced amylose content is controlled by 2 recessive genes. Thus, we isolated a rice mutant with enhanced amylose content in the endosperm without affecting the amylopectin structure. As global warming or higher maturation temperatures decrease the amylose content in rice endosperms, the mutant obtained in this study would be useful in breeding programs to diversify grain quality and to understand the genetic and molecular mechanisms of amylose synthesis.
