EVIDENCE OF ASSOCIATION BETWEEN SPECIFIC HEAT-SHOCK PROTEIN(S) AND THE DROUGHT AND HEAT TOLERANCE PHENOTYPE IN MAIZE

Although differences in hear-shock protein (HSP) patterns and differen ces in heritable drought and/or heat tolerance have been documented, t here is no genetic evidence of association of the drought and/or heat tolerance with specific alterations in HSP expression in crop plants. In this study we tested the hypothesis that specific maize HSP(s) is(a re) associated with plant ability to withstand soil drying (drought) a nd heat stress. We previously identified a line of maize, ZPBL 1304, w hich is tolerant to drought and heat stress and synthesizes a 45 ku (k Da) HSP(s), and a line of maize, ZPL 389, which is sensitive to drough t and heat stress and does not synthesize the 45 ku HSP(s) (Ristic et al., 1991). We investigated possible association of the 45 ku HSP(s) o f ZPBL 1304 line with the drought and heat tolerance phenotype. The tw o lines, ZPBL 1304 and ZPL 389, were crossed, and dehydration avoidanc e, damage to cellular membranes, and pattern of HSP synthesis were inv estigated in Fz plants after exposure to soil drying and high temperat ure (45 degrees C) stress conditions. The 45 ku HSP(s) of ZPBL 1304 li ne was(were) associated with the drought and heat tolerance phenotype. The synthesis of 45 ku HSP(s) was observed in F-2 plants that display ed an increased ability to recover from soil drying and heat stress. I t is possible that either the 45 ku HSP(s) play a role in recovery fro m drought and heat stress or their gene(s) are in close proximity to t he gene(s) which encode tolerance to drought and heat stress.