The roles of the atDjA2 and atDjA3 molecular chaperone proteins in improving thermotolerance of Arabidopsis thaliana seedlings

AtDjA2 and atDjA3 are members of J-domain molecular chaperone family of Arabidopsis thaliana. Analysis of the spatial expression of promoter:GUS fusions showed that both genes are expressed in young roots and leaves of seedlings, as well as in flowers and young siliques. The results from quantitative real-time PCR analyses indicate that the expression of both genes increased rapidly after a 37 °C heat shock. Similar results were seen when the promoter:GUS fusion plants were exposed to heat shock conditions. The heat shock-induced increase in atDjA3 gene expression was more rapid and to a greater extent than seen with the atDjA2 gene. Both T-DNA insertional KO lines and ectopic 35S-driven overexpressing lines of both genes were employed in an attempt to specific roles for the two genes. The individual T-DNA insertional mutants had no obvious physical phenotype, however, seedlings of double-KO lines had impaired thermotolerance. Conversely, ectopic overexpression of both genes resulted in plants with increased thermotolerance. These results suggest a conserved function for both genes, and a dose-dependent effect on seedling thermotolerance.