Relation of protein synthesis in imbibing wheat embryos to the cell-free translational capacities of bulk mRNA from dry and imbibing embryos

Abstract

Dry wheat embryos were allowed to imbibe water in the presence or absence of an inhibitor of mRNA synthesis (alpha-amanitin). At each of a series of times after the onset of imbibition, newly synthesized polypeptides were labeled, isolated, and compared with those made by cell-free translation of RNA prepared from the same embryos. In the absence of alpha-amanitin, characteristic time-dependent changes in the relative proportions of many polypeptides in the electrophoretic distributions of proteins synthesized in imbibing wheat embryos could be correlated with parallel changes in the cell-free translational capacity of bulk mRNA from the same embryos. These changes were virtually eliminated when alpha-amanitin was present in the imbibing medium. The findings are consistent with the possibility that transcription of new mRNA, which begins with the onset of imbibition, is responsible for change in the electrophoretic distributions of nascent polypeptides between 40 min and 5 h postimbibition of dry wheat embryos (Cuming, A. C. & Lane, B. G (1979) Eur. J. Biochem. 99, 217-224). Allied with the principal investigation, a useful modification has been developed in order to obtain an improved field of resolution (encompassing a range of Mr values between less than 5 X 10(5) and greater than 200 X 10(3), without using a gradient in sodium dodecyl sulfate/polyacrylamide gel.