Heat shock proteins in Sorghum bicolor and Pennisetum americanum. II. Stored RNA in sorghum seed and its relationship to heat shock protein synthesis during germination

Abstract. During the germination of sorghum, heat shock proteins (HSPs) are synthesized in response to high‐temperature stress at the onset of imbibition. HSP72 and HSP83 are apparently synthesized without a heat shock induction in the first 2 h of imbibition. The presence of RNA encoding HSPs in the quiescent embryo, and in the 2 h imbibed embryo, was confirmed by in vitro translation of RNA isolated from dry mature sorghum seeds. By 24 h of imbibition at 35°C, no translatable RNA was evident for these HSPs unless a heat shock treatment was also given. Treatment of imbibing embryos with cordycepin inhibited RNA synthesis. Protein synthesis was not affected so greatly and HSP synthesis was still inducible although at reduced levels. The involvement of RNA stored in the seed and of de novo transcription in protein synthesis during imbibition is discussed.