In temperature stress, the main role of heat-shock proteins (HSP) is to act as molecular
chaperones for other cellular proteins. However, knowledge about the hormonal regulation of the
production of the HSP is quite limited. Specifically, little is known about the role of the plant steroid
hormones—brassinosteroids (BR)—in regulating the HSP expression. The aim of our study was to
answer the question of how a BR deficit or disturbances in its signaling affect the accumulation of
the HSP90, HSP70, HSP18, and HSP17 transcripts and protein in barley growing at 20C (control)
and during the acclimation of plants at 5 C and 27 C. In barley, the temperature of plant growth
modified the expression of HSPs. Furthermore, the BR-deficient mutants (mutations in the HvDWARF
or HvCPD genes) and BR-signaling mutants (mutation in the HvBRI1 gene) were characterized by
altered levels of the transcripts and proteins of the HSP group compared to the wild type. The
BR-signaling mutant was characterized by a decreased level of the HSP transcripts and heat-shock
proteins. In the BR-deficient mutants, there were temperature-dependent cases when the decreased
accumulation of the HSP70 and HSP90 transcripts was connected to an increased accumulation of
these HSP. The significance of changes in the accumulation of HSPs during acclimation at 27 C and
5 C is discussed in the context of the altered tolerance to more extreme temperatures of the studied
mutants (i.e., heat stress and frost, respectively)
