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Regulation Of Gene Expression In Corn (Zea Mays L.) By Heat Shock

Chris L. Baszczynski, David B. Walden, Burr G. Atkinson

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Subjecting 5-day-old plumules of corn (Zea mays L.) to elevated temperatures for brief periods of time causes the pattern of protein synthesis to shift from the production of a broad spectrum of proteins to the new and (or) enhanced synthesis of a small number of heat-shock polypeptides (HSPs). Most notable is the depressed synthesis of a major polypeptide (relative mass (Mr) = 93 000 and isoelectric point = 8.0) normally made at 27 °C and the enhanced and (or) new synthesis of polypeptides with Mrs of 108 000, 89 000, 84 000, 76 000, 73 000, and 18 000, following 1 h of heat shock. These six HSPs resolve into 18 spots by two-dimensional fluorographic analysis. The induction of the HSPs requires temperatures at or exceeding 35 °C for detectable synthesis. Some of the HSPs are synthesized following only 15 min at 41 °C and synthesis of all HSPs is observed within 120 min following heat shock. Recovery from heat shock is rapid; after 6 to 8 h at 27 °C following heat shock, the polypeptide pattern is indistinguishable from me control. Extracts from individual heat-shocked shoots produced polypeptide synthetic patterns identical to those from extracts from 20 shoots, regardless of whether single shoots were intact or excised during labelling. Single 5-day-old primary roots exhibited polypeptide synthetic patterns and responded to heat shock in a manner similar to shoots. This is the first demonstration of the induction of heat-shock polypeptides in a whole, intact higher plant.