Relationship between Mutations of the Pectin Methylesterase
Gene in Soybean and the Hardness
of Cooked Beans
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Abstract
Hardness of cooked soybeans [<i>Glycine max</i> (L).
Merr.] is an important attribute in food processing. We found one
candidate gene, <i>Glyma03g03360</i>, to be associated with
the hardness of cotyledons of cooked soybeans, based on a quantitative
trait locus and fine-scale mapping analyses using a recombinant inbred
line population developed from a cross between two Japanese cultivars,
“Natto-shoryu” and “Hyoukei-kuro 3”. Analysis
of the DNA sequence of <i>Glyma03g03360</i>, a pectin methylesterase
gene homologue, revealed three patterns of mutations, two of which
result in truncated proteins and one of which results in an amino
acid substitution. The truncated proteins are presumed to lack the
enzymatic activity of Glyma03g03360. We classified 24 cultivars into
four groups based on the sequence of <i>Glyma03g03360.</i> The texture analysis using the 22 cultivars grown in different locations
indicated that protein truncation of Glyma03g03360 resulted in softer
cotyledons of cooked soybeans, which was further confirmed by texture
analysis performed using F<sub>2</sub> populations of a cross between
“Enrei” and “LD00-3309”, and between “Satonohohoemi”
and “Sakukei 98”. A positive correlation between hardness
and calcium content implies the possible effect of calcium binding
to pectins on the hardness of cooked soybean cotyledons