In vitro translation of long-lived mRNA from dry wheat seeds

The mRNAs from germinated and ungerminated wheat seeds were purified and translated in both wheat germ extract and rabbit reticulocyte lysate systems. The transla­ tion activity of poly(A)+RNA from dry aleurone layers was less than those of seedlings and dry embryos in both systems. The poly(A)+RNAs from seedlings and dry embryos were translated into high molecu­ lar weight, whereas that from aleurone layers was translated into low molecular weight. The polypeptide synthesized in vitro was immunoprecipitated using rabbit anti-wheat a -amylase antibody and goat anti-rabbit IgG antibody. Fluorography after SDS-polyacryl­ amide gel electrophoresis of the immunoprecipitated translation products of poly(A)+RNAs from seedlings and dry embryos showed a band of molecular weight 43,000 (the same as that of the a-amylase precursor polypeptide), but that from aleurone layers was not. Ratios of immunoprecipitate to the total translation products were 0.9% using goat anti-rabbit IgG antibody and 0.4% using Protein A-Sepharose. Various dry seeds or embryos are shown to contain long-lived mRNA, but little is known about its functions. Although the synthesis of new mRNA occurs rapidly after the onset of imbibition, the level of early protein synthe­ sis is largely sustained by stored mRN A (THOMPSON and LANE, 1980). ASPART et at. (1984), using radish embroyos, reported that the polypeptides synthesized during the first 15 min of germination are encoded by stored mRNA, and also that some stored mRNAs are not remnants of mRNA present during embryogenesis, but code for polypeptides playing a particular role in early germination. Several groups have identified the translation products of mRNA which are conserved in dry embryos, and they include lectin (PEUMANS et at., 1980), mung bean albumin (CARLIER et at., 1980) and wheat ribosome proteins (CUMING and LANE, 1979). T ANEJA and SACHAR (1976) suggested from experiments using inhibitors of RNA synthesis that three enzymes (o-diphe­ nolase, peroxidase, and RNase) are translated from stored mRN A. In this study, poly(A)+RNA was isolated from 48-h germinated seedlings, dry embryos, and aleurone layers. Poly(A)+RNAs were translated with In