Dehydration, damage to cellular membranes, and heat-shock proteins in maize hybrids from different climates

We recently described a band of HSP(s) of 45 ku (kDa) in the leaf tissue of a drought and heat-resistant maize line, ZPBL 1304 (Ristic et al., 1991). This band had not been previously described in the leaves of maize and does not appear to be common in higher plants. It is not known whether this band of HSP(s) of 45 ku is unique to the ZPBL 1304 line or if a band of HSP(s) of similar molecular weight also exist in other maize genotypes. Pioneer Hi-Bred International, Inc. has developed sixteen hybrids of maize. These hybrids have been bred for resistance to drought and heat in three, climatically different, geographical regions: southern, central, and northern United States. We hypothesize that hybrids from climatically differing environments have different abilities to withstand drought and high-temperature stress conditions and synthesize specific HSPs. The objectives of this study were to determine: 1) whether Pioneer hybrids synthesize HSPs of similar molecular mass to that of the 45 ku HSP(s) found in ZPBL 1304 maize line, 2) whether hybrids from climatically differing environments differ in their abilities to resist drought and high-temperature stress conditions, and 3) whether hybrids from climatically differing environments differ in the possible synthesis of 45 ku HSP(s). Our previous observation of the 45 ku HSP(s) was not unique to a single maize line. The 45 ku HSP(s) were synthesized in maize hybrids that have been bred for resistance to drought and heat. Southern hybrids displayed greater ability to withstand drought and heat stress conditions than central and northern hybrids. Also, southern hybrids showed greater ability to synthesize HSP(s) of 45 ku than northern hybrids. It is possible that the 45 ku HSP(s) we found play a role in the development of drought and heat resistance in maize.