Heat Shock Protein Expression in Thermotolerant and Thermosensitive Lines of Cotton

A large proportion of the water absorbed by a plant is used to cool its leaves as the air temperature becomes too hot. If the molecular basis of heritable thermotolerance were understood, then improvements in water use by crop plants might be possible. The role of heat shock proteins (HSPs) in the expression of heritable thermotolerance in cotton was investigated. Comparisons were made between the expression of HSPs in genetically characterized heat-tolerant and heat-sensitive lines of cotton. These Comparisons were based on electrophoretic analysis of in vivo labelled proteins. No differences were observed between the two lines with regard to (1) the temperature at which HSPs synthesis was induced (37oC), or the temperature at which HSP synthesis was maximal (45oC), (2) the rates of recovery from HSP synthesis or in the duration of HSP synthesis, and (3) the major size classes of HSPs expressed in these two lines. Several unique HSPs were identified on two-dimensional gels: a 26 kDa HSP which displayed in a heat-tolerant BC3 individual was that of the heat-sensitive parent. No alteration in HSP expression could be found which correlated with the heritable thermotolerance.