SELECTION OF CULTURED WHEAT CELLS FOR TOLERANCE TO HIGH-TEMPERATURE STRESS

In vitro culture offers approaches to study cellular responses and to obtain cells tolerant to high temperature stress. The objectives of th is study were to select wheat cells that tolerate high temperature str ess, study cell line stability and cytogenetic characteristics, and co mpare protein synthesis in selected and control cell lines after expos ure to heat stress. Three of 600 colonies plated were recovered after cells had been exposed to 48-degrees-C. Forty-five percent of the cell s of the tolerant cell line, M48 survived when they were returned to a normal temperature (22-degrees-C) for 6 mo and rechallenged with a 48 -degrees-C treatment. The control cell line exhibited 0.8% survival un der this treatment. Chromosomal elimination and genomic rearrangements were observed extensively for the cell lines before and after heat se lection. Heat selection did enhance the occurrence of polytene chromos omes and the frequency of extrachromosomal DNA. When cell viability wa s evaluated in cell suspension cultures, M48 had a higher percentage o f viable cells than the control cell line. Analysis of S-35-methionine in vivo labeled proteins showed that the selected M48 cell line maint ained the synthesis of most normal proteins under a heat shock of 40-d egrees-C for 4 h, with synthesis of several unique low molecular weigh t heat-shock proteins (HSPs). A quantitative increase in high molecula r weight HSPs was also observed in this cell line. This study demonstr ated that a heat-tolerant cell line of wheat can be obtained from in v itro selection, and that this phenomenon was associated with the synth esis of specific proteins under heat stress.