In this article we will discuss about the effect of heat stress on plants.
Elevation in the temperature of surrounding environment imposes heat stress on wide range of organisms. Heat stress is responsible for the induction of several heat inducible genes, commonly referred as heat shock genes, which encodes heat shock proteins. Expressions of heat shock genes are prevalent in both prokaryotic and eukaryotic systems.
There are five classes of heat shock proteins, of which only four are well conserved. These four have been categorized based on their sizes as Hsp 60, Hsp 70, Hsp 90 and Hsp 100. The constitutive expressions of most of these proteins protect intracellular proteins against heat stress.
Due to their thermotolerant nature their expression can be induced by heat treatment in presence of conserved heat shock elements (HSE) in the promoter of heat shock genes, which play a crucial role triggering transcription in response to heat. These cis-acting elements consist of alternating units of pentameric nucleotide (5′-nGAAM-3) that serve as a binding site for heat shock factor (HSF).
Thermotolerance against heat stress have been accomplished in plants transferred with heat shock regulatory proteins. The rapid heat-shock responses are perceived by heat-shock transcription factor (HSF) and are able to bind to heat shock element.
Since all heat shock genes contain HSE conserved sequence, overexpression of HSF gene inturn turned on almost all heat shock genes and consequently provides protection against heat stress.