Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Exposure of intact maize seedlings to high temperature (e.g. a 25{dollar}\sp\circ{dollar}C to 42{dollar}\sp\circ{dollar}C shift) rapidly alters patterns of polypeptide synthesis in plumules and radicles. Synthesis of many polypeptides normally made under 'control' conditions (25{dollar}\sp\circ{dollar}C) is reduced and new and/or enhanced synthesis of a group of heat shock polypeptides (HSPs) is induced (108 kD, 89 kD, 84 kD, 76 kD, 73 kD, 23 KD and 18 to 19 kD). Certain heavy metals and the insecticide methomyl cause similar alterations in the patterns of polypeptide synthesis in maize plumules and/or radicles. Synthesis of 'control polypeptides,' including a major 93 kD polypeptide, is reduced and new and/or enhanced synthesis of polypeptides with M{dollar}\sb{lcub}\rm r{rcub}{dollar}s and pIs similar to the maize HSPs is induced. Antibodies raised against the 18 to 19 kD maize HSPs recognize 18 to 19 kD polypeptides synthesized by plumules and/or radicles in response to treatment with the heavy metals, Cadmium, Zinc or Copper, or in response to methomyl treatment.;The intensity of the response generated in maize plumules or radicles depends on the stressor, the concentration used and on the tissue treated. No stressor used in this study induces the quantity of HSP synthesis induced by heat shock (a 25{dollar}\sp\circ{dollar}C to 42{dollar}\sp\circ{dollar}C shift).;Patterns of polypeptide synthesis in methomyl-treated plumules of maize seedlings that possess a normal mitochondrial genome or a mitochondrial genome encoding methomyl sensitivity (cytoplasmic male-sterile T; cms-T) are similar at all methomyl concentrations tested. Methomyl sensitivity of cms-T plants is due to the uncoupling of oxidative phosphorylation in mitochondria. The demonstration that possession of methomyl-sensitive mitochondria has no effect on induction characteristics of HSP-like polypeptides by methomyl, suggests that the uncoupling action of methomyl is not related to the induction of HSP-like polypeptide synthesis by methomyl.;A preliminary characterization of mRNAs encoding 18 to 19 kD HSPs in heat-shocked maize plumules by size fractionation and in vitro translation analyses reveals that the mRNAs encoding 18 to 19 kD HSPs are 0.6 to 0.95 kb in size.



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