Heat Stress Signal Transduction in Plant Cells

Plant tolerance to heat stress proved to be entirely dependent on thesignaling flow of information by which the plant can sense the changes in itssurrounding environment and signal its genes to respond by producingspecial proteins to protect it-self. Any changes or manipulations in thissignaling flow of information will presumably lead to a modification in thegenetic expression inside the plant cells, consequently, changing plantperformance. Understanding these signaling events in response to heat mayhelp us to produce heat tolerant plants capable to stand high temperaturestress. In the present investigation, the results showed that a heat activatedMAP kinase cascade, involving heat activated MAP kinase (HAMK), playedan essential role in heat shock gene expression in tobacco BY-2 cells. Inorder to determine if heat activation of HAMK involved additional pathwaysof signaling we studied the upstream regulation of HAMK, includingmembrane fluidization and reorganization of cytoskeleton. The activation ofHAMK and accumulation of heat responsive HSFs, HSP70 and HSP27proteins were used as end-point markers in these experiments. It isconcluded that the heat shock response, as measured by HAMK activationand heat shock proteins accumulation required PKC activation, membranefluidization and reorganization of the cytoskeleton. A comparativebioinformatic explanation of similarities between tobacco heat shock genesand their counterparts in different organisms revealed a high degree ofevolutionary conservation in the corresponding domains, indicating similarfunction in different species.