Relationship between pectin methylesterase, calcium, and the hardness of cooked beans
2018
Toda, K. (Institute of Crop Science, NARO, Tsukuba, Ibaraki (Japan))
The texture of softer cooked soybeans [Glycine max (L). Merr.] is preferable for soy products such as cooked beans (nimame), fermented steamed beans (natto), soy sauce, and fermented steamed bean paste (miso). We found a candidate gene, Glyma03g03360, associated with the hardness of cotyledons in cooked soybeans using a quantitative trait locus analysis of a recombinant inbred line population developed from a cross between two Japanese cultivars, 'Natto-shoryu' and 'Hyoukei-kuro 3'. Glyma03g03360 encodes a pectin methylesterase gene. Analysis of the DNA sequence revealed three mutation patterns, two of which result in truncated proteins and one of which results in an amino acid substitution. The truncated Glyma03g03360 proteins are presumed to lack enzymatic activity. Texture analysis of soybean cultivars with different Glyma03g03360 genotypes indicated that truncation of Glyma03g03360 resulted in softer cotyledons of cooked soybeans, which was further confirmed by texture analysis performed using F2 populations of crosses between 'Enrei' and 'LD00-3309', and between 'Satonohohoemi' and 'Sakukei 98'. These results, and the relationship between calcium content and cotyledon hardness, support the idea that pectin methylesterase mainly affects the hardness of cooked soybean by controlling the degree of pectin methoxylation.
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