The response of maize to heat shock has been examined in several tissues and genotypes to determine the extent to which these 'factors' influence the response. Polypeptides from 3-5 day old shoots and primary roots, and 25-30 day old leaves were radioactively labelled, extracted and separated by 1D and 2D PAGE as described elsewhere (Baszczynski et al. 1982, Canad. Jour. Biochem., April). The results show that all three tissue types, although differing in control polypeptide patterns, respond to heat shock in a similar manner with the new and/or enhanced synthesis of the six Mr classes of HSPs described in the previous contribution (this Newsletter). Roots, however, do not show a marked depression in the synthesis of the 93 kd polypeptide as noted in the shoots and leaves.

When returned to the control temperature (27 C), shoots exhibit almost complete recovery after two hours while roots and leaves take longer to recover.

A comparison of different genotypes, including Oh43 (an inbred dent), Gaspe Flint (an inbred flint) and PX-11 (a commercial hybrid, Northrup-King) indicate that the genotypes differ in Coomassie blue-stained gels and fluorograms of polypeptide patterns when plants are grown at the control temperature of 27 C and show a similar response when subjected to an elevated temperature. The genotypes differ largely in the relative amounts of synthesis of the heat shock polypeptides.

We are currently examining a series of the temperature-sensitive, virescent mutants in a common background (Oh43) to determine if differences in the greening temperature optima among the virescents (Hopkins and Walden, J. Hered. 68:282-286, 1977) are reflected in their differential capacity to synthesize heat shock proteins.

C. L. Baszczynski, J. G. Boothe, D. B. Walden and B. G. Atkinson

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