EXPRESSION OF A UNIQUE PLASTID-LOCALIZED HEAT-SHOCK-PROTEIN IS GENETICALLY LINKED TO ACQUIRED THERMOTOLERANCE IN WHEAT

We have used a combination of molecular and classical genetic approach es to delineate the relationship between a specific HSP member and cel l viability under heat stress, Using recombinant inbred lines (RILs) o f wheat, derived from a cross of the thermotolerant cultivar 'Mustang' and the thermosusceptible cultivar 'Sturdy,' we have identified a uni que HSP and a differentially expressed cDNA sequence, both related to the plastid-localized HSP26 gene family, that are closely associated w ith acquired thermotolerance in wheat. An isoform of HSP26 was synthes ized under heat stress in all examined thermotolerant RILs and 'Mustan g', and was absent in all examined thermosusceptible RILs and 'Sturdy. ' Using a modified differential-display method, we have also identifie d a gene-specific cDNA sequence that is similar to other known members of the wheat HSP26 gene family and is selectively expressed in 'Musta ng' and most of the examined thermotolerant RILs, but not expressed in 'Sturdy' and all the thermosusceptible RILs. These results suggest a genetic linkage between the acquired thermotolerance trait and the dif ferential expression of a unique member of the HSP26 gene family.