Heat Shock Proteins: Classification, Functions and Expressions in Plants during Environmental Stresses

HSPs proteins are found mostly in every cell from prokaryotes to eukaryotes. HSPs have been comprehensively studied in animals and humans. Recently their role in plants was thoroughly studied. HSPs were described as a result of heat shock conditions, but now get activate by various stresses like Ultraviolet light, cold, wound healing, drought, salinity and pathogenic infections (Lindquist et al., 1988). The term “heat shock protein” is now incorrect because HSPs are not expressed only under high temperature, also expressed under other stresses. HSPs are essential in maintaining balanced cell internal conditions under optimum and damaged growth conditions about in all living cells (Wang et al., 2004). Many types of HSPs are function as chaperon proteins that assist in folding upon folding of three dimensional proteins or proteins that get denatured by stress within the cell. Therefore many folding proteins are considered as HSPs due to their folding nature in response to stress (Wang et al., 2004). It also functions in the stability of cellular proteins and have role in protein refolding under diverse environmental conditions (Huttner et al., 2012). HSPs that respond to stresses mainly located in cytoplasm. It is suggested that HSPs have dynamic and diversified role in protein homeostasis because of its ubiquitous nature in living cell. HSPs are generally found in fungi plants and animals, HSP transcripts expression were upregulate at extreme temperature (Lindquist et al., 1986). Under normal physiological conditions HSPs are localized in the cytoplasm but translocate to the nucleus under stresses.