Synthesis of a family of 45 ku heat shock proteins in a drought and heat resistant line of maize under controlled and field conditions

Previous studies have shown that the leaf tissue of a drought and heat resistant line of maize (Zea mays L.) ZPBL 1304 synthesizes unique heat shock proteins (HSPs) of 45 ku (kDa) (Ristic et al., 1991). The synthesis of 45 ku HSPs, however, has been studied only at 45 degrees C and in young (3-week-old) plants. In this study, we have further characterized the synthesis of 45 ku HSPs in the ZPBL 1304 line by investigating: 1) the temperature range of their synthesis, 2) the possible impact of exogenous abscisic acid (ABA) on their synthesis, 3) the possible synthesis of 45 ku HSPs in root tissue, and 4) the possible synthesis of 45 ku HSPs in mature plants (plants at the flowering stage) under field conditions. The 45 ku HSPs of the ZPBL 1304 maize line were synthesized over a broad temperature range starting from 35 degrees C upwards, and the synthesis of these HSPs increased with increasing temperature. Treatment with ABA did not seem to have an effect on the induction and synthesis of the 45 ku HSPs. Poor tissue did not accumulate HSPs of 45 ku during heat shock. Instead, roots accumulated HSPs of 39 ku, 47 ku, and 52 ku. Field-grown mature plants of the ZPBL 1304 line were found to synthesize the 45 ku HSPs. It is possible that maize HSPs of 45 ku may be important in the development of heat resistance under field conditions.