Exposure of maize seedlings to heat-shock induces the synthesis of a set of heat shock polypeptides (MNL 6:111, 1982). Treatment of maize seedlings with a variety of other stressors induces synthesis of a set of polypeptides with Mr's similar to the heat-shock polypeptides (MNL 60:92, 1986; MNL 61:69, 1987). The 18kd polypeptides induced by cadmium chloride treatment and by treatment with the insecticide lannate (methomyl-C6H10N2OS2) are recognized by antibodies raised against 18kd heat-shock polypeptides (MNL 61:69, 1987). The similarity in Mr's of the polypeptide sets and the antigenic similarity of the 18kd polypeptides induced by different stressors led to the suggestion that heat-shock polypeptide synthesis is a general response to stress in maize.
Here we report on a comparison of 2D IEF-SDS PAGE profiles of newly synthesized polypeptides from maize seedlings treated with the following stress-inducing agents: cadmium chloride, zinc sulphate, copper sulphate, lead nitrate and lannate (methomyl).
Plumules or radicles of intact 5-day-old maize seedlings (Oh43) were immersed in treatment solution for 3 hours . 35S-methionine was added during the last 2 hours of treatment. Extracted proteins were separated by 2 D IEF-SDS-PAGE and fluorograms were compared. The pI's of the polypeptides induced by the different stressors were indistinguishable from those of the heat-shock polypeptides (HSPs). The relative amount of radioactivity in the HSP-like polypeptides varied among different stressors. The concentration of each agent found to induce synthesis of HSP-like polypeptides are given in the table, along with the relative amount of radioactivity in the HSP-like polypeptides in comparison with the amount found following heat shock.
This study is being repeated using the genotype Oh51A. Preliminary results show that the relative amount of radioactivity incorporated into HSP-like polypeptides is significantly higher in Oh51A than in Oh43 following treatment with the insecticide methomyl (lannate).
Carol A.B. Rees and David B. Walden
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