Some aspects of the synthesis of long-lived messenger ribonucleoproteins in developing rye embryos.

Untranslated messenger ribonucleoproteins (mRNPs informosomes) are present in developing rye (Secale cereale, L. cv. Celestijner) embryos throughout the last 5 weeks of seed formation. Ribosomal as well as non-ribosomal ribonucleoproteins are formed continuously both in primary axes and scutella until any synthesis of macromolecules stops upon dessication. The content of preformed messengers in the primary axes of precociously harvested rye grains increases as a function of embryo development. This increase of the "template load" of the primary axes results from a continuous accumulation of qualitatively identical mRNPs. Germination experiments demonstrated that at least most of the preformed messengers are not required for the germination process. Their function is discussed in terms of selective adaptation to unfavorable conditions.