Lodgepole pine seed germination. III. Patterns of protein and nucleic acid synthesis in the megagametophyte and embryo

Abstract

A study of lodgepole pine (Pinus contorta Dougl.) seeds following imbibition at 28 °C has shown that in the megagametophyte, RNA and DNA levels remained constant until 5 days after imbibition when a decrease occurred. In the embryo, increases in RNA and DNA occurred 2 and 5 days after imbibition, respectively. Incorporation of [3H]uridine into total RNA was maximum by 2 days after imbibition in both the megagametophyte and the embryo. Incorporation of [3H]leucine into buffer-soluble protein showed a similar trend for both organs except that maximum incorporation occurred by 3 days after imbibition. An electrophoretic analysis of buffer-soluble proteins synthesized following the incorporation of [35S]methionine showed similar patterns for both the megagametophyte and the embryo. In both organs, the synthesis of three subsets of proteins was recognized. One subset was synthesized in the mature seed. Synthesis continued through germination but was terminated prior to radicle emergence. Synthesis of a second subset coincided with radicle emergence and continued during early seedling growth. A third subset was synthesized constitutively throughout germination and early seedling growth. Keywords: nucleic acid synthesis, protein synthesis, seed germination, lodgepole pine.