Heat-shock proteins induce heavy-metal tolerance in higher plants

Abstract

Abstract. Cell cultures of Lycopersicon peruvianum L.stressed with CdSO 4 (10-3M) show typical changes in the ultrastructure, starting with the plasmalemma and later on extending to the endoplasmic reticulum and the mitochondrial envelope. Part of the membrane material is extruded, with the formation of osmiophilic droplets which increase in size and number during the stress period. After 4 h, about 20% of the cells are dead. A short heat stress preceeding the heavy-metal stress induces a tolerance effect by preventing the membrane damage. The cells show a normal ultrastructure with one exception: cytoplasmic heat-shock granules are formed. This protective effect can be abolished by cycloheximide. Cadmium uptake is not markedly influenced by the heat stress. Cadmium is found together with sulfur in small deposits in the vacuoles of stressed cells. The precipitates contain an excess of sulfur, evidently due to the stress-induced formation of phytochelatins. The role in heavy-metal tolerance of heat-shock proteins in the plasmalemma (HSP70) and in cytoplasmic heat-stress granules (HSP17, HSP70) is discussed.

Plant Responses to Heavy Metal Toxicity

“…HSPs are found in all cells and are expressed not only in response to elevated temperatures but also to other stresses, including heavy metals, where they protect and repair proteins, and act as molecular chaperones to ensure correct folding and assembly (Vierling 1991). For example, heavy metals induce the expression of low molecular weight HSPs in rice (Tseng et al 1993), and in cell culture of S. vulgaris and Lycopersicon peruvianum (Wollgiehn and Neumann 1999), the latter also producing the larger protein HSP70 (Neumann et al 1994). HSP70 is localized in the nucleus and the cytoplasm, and is also found at the plasma membrane suggesting a protective role for membranes.…”

Phytoremediation Using Algae and Macrophytes: I

“…Several heavy metal tolerance mechanisms within the plants have been suggested by various researchers (Mazen 2004 ;Hall 2002 ) including: (1) synthesis of metal-binding compounds such as amino acids, citric acid, malic acid, and phytochelatins (PCs) (Reilly 1972 ;Thurman and Rankin 1982 ;Brookes et al 1981 ;Grill et al 1985, Rtiegsegger and Brunold 1992Cobbett and Goldsbrough 2002 ;Hall 2002 ); (2) alterations of membrane structures (De Vos et al 1988 ); (3) complex formation in vacuoles (Fernando and Fernando 1994 ); and (4) synthesis of stress metabolites including proteins (Neumann et al 1994 ). It is also evident that of the abovementioned mechanisms more than one mechanism may be working together in the same species (Hall 2002 ).…”

Physiological Variation and Accumulation of Metals in Two Growth Forms of Lichens Growing Around Panki Thermal Power Plant of Uttar Pradesh, India.

“…Increase in protein due to stressed condition has been reported in higher plants by Neumann et al (1994). Overall pattern showed the concentration varied with the wind direction of the area as well as increasing trend with the increasing distance from the thermal power plant.…”