Exogenous methionine depresses level of mRNA for a soybean storage protein.

In vitro translation experiments indicate that absence of the beta-subunit of 7S storage protein in soybean (Glycine max L. Merr. cv. Provar) cotyledons cultured on methionine-supplemented medium is due to lack of functional mRNA for that polypeptide. Relative amounts of functional mRNA for the 7S alpha'- and alpha-subunits were unaffected by methionine in the cotyledon culture medium. Measurements of beta-subunit accumulation in cotyledons transferred from basal medium to methionine-supplemented medium show that methionine inhibits continued accumulation of the beta-subunit after synthesis of the beta-subunit has begun, and that methionine does not promote degradation of existing beta-subunit.