Spatiotemporal expression patterns of cytosolic AtHSP90-2 in Arabidopsis seedlings

Heat shock protein AtHSP90-2 is one of the three constitutive cytosolic HSP90s of Arabidopsis thaliana, which are highly homologous and show mild expression activation in response to stressful impacts. To characterize the functioning of AtHSP90-2, we have analyzed tissue-specificity of its expression during seedling development using a DsG transgenic line carrying a loss-of-function mutation of AtHSP90-2 via translational fusions with the β-glucuronidase reporter gene (GUS). Histochemical analysis during the first two weeks of seedling growth revealed AtHSP90-2 expression in all organs, as well as differences in its intensity between tissues and showed its dynamics. The tissue-specific AtHSP90-2-GUS expression pattern was shown to be maintained under heat shock and water deficit. The most prominent GUS staining was detected in the vascular system and hydathodes of cotyledons, and stipules. The basipetal gradient of AtHSP90-2 expression during leaf formation, its dynamics in developing stipules, and the high level of its expression in cells with active transport function suggest a special role for the gene in certain cellular processes.