Association of 70-Kilodalton Heat-Shock Cognate Proteins with Acclimation to Cold

Abstract

Exposure of young spinach seedlings (Spinacia oleracea L. cv Bloomsdale) to 5 C leads to an increase in the synthesis of several 79-kilodalton proteins that are present in leaf tissue grown at 200 C. Protein sequence analyses and immunological cross-reactivity indicate that this group of proteins belongs to the 70-kilodalton heatshock family. Steady-state transcript levels and protein synthesis are increased two-to threefold within 1 day, but immunoblot analyses suggest that the steady-state concentration of this protein group in leaf tissue only gradually accumulates at low temperature. It is proposed that the increased synthesis of several members of the 70-kilodalton heat-shock family could result from an influence of low temperature on protein folding and/or assembly processes.Plants are poikilotherms and must be able to adjust to changes in ambient temperature to ensure survival. In keeping with this need to adjust to a changing environment, polar, temperate, and alpine perennial plants follow a cyclical rhythm of growth and dormancy. In these plants, the cessation of vegetative growth and onset of dormancy is a prerequisite for the induction of tolerance to the stresses imposed by freezing (35). Collectively, the set of biochemical and physiological events that augments a plant's tolerance to low temperature stress is termed cold acclimation (35). In hardy plants, cold acclimation performs two major functions: (a) the adjustment of cellular metabolism and function to the kinetic and biophysical constraints imposed by reduced temperature, and (b) the induction of freezing tolerance (11).At low nonfreezing temperatures that promote cold acclimation, many plant species exhibit subtle changes in gene expression (11,15)

A cold-responsive wheat (Triticum aestivum L.) gene wcor14 identified in a winter-hardy cultivar 'Mironovska 808'.

“…Dehydrins (DHN)/late embryogenesis abundant proteins (LEA)/proteins responsive to abscisic acid (RAB) are the well known classes of COR proteins. Some COR proteins, like Arabidopsis KIN1, show structural similarities to antifreeze proteins (Kurkela and Franck, 1990) and others to a HSP70 chaperon family which is known to have roles in protein transport, folding and assembly/disassembly processes (Neven et al, 1992). Although physiological function of these different classes of COR proteins remains largely unknown, some showed a positive correlation with the degree of freezing tolerance which is enhanced by cold acclimation (Monroy et al, 1993;Houde et al, 1995;Jaglo-Ottosen et al, 1998).…”

Cold-Induced Accumulation of hsp90 Transcripts in Brassica napus

“…It is postulated that proteins that display these distinctive properties may have roles in cryoprotection (Thomashow, 1993). Other cold-regulated gene products show similarities to antifreeze proteins (Kurkela and Franck, 1990) or to drought-induced late-embryogenesis-abundant proteins (Gilmour et al, 1992;Neven et al, 1993) and responsive to ABA proteins (Vilardell et al, 1990;Lang and Palva, 1992), which suggests a possible role in preventing ice formation and imparting tolerance to dehydration stress, respectively .…”

Analysis of the stress-inducible transcription factor SsNAC23 in sugarcane plants

“…This hsp70 from sugarcane could be part of the group of proteins responsible for SsNAC23 translocation from the place of synthesis (cytoplasm) to where it functions (nucleus). Curiously, a spinach homologue of the maize hsp70 has increased levels during spinach cold acclimation (Neven et al, 1992). Recently it was demonstrated that this protein, denominated Hsc70, has chaperone activity in plants of spinach exposed to cold stress (Zhang and Guy, 2006).…”