Purification and in Vitro Chaperone Activity of a Class I Small Heat-Shock Protein Abundant in Recalcitrant Chestnut Seeds

Abstract

A 20-kD protein has been purified from cotyledons of recalcitrant (desiccation-sensitive) chestnut (Castanea sativa) seeds, where it accumulates at levels comparable to those of major seed storage proteins. This protein, termed Cs smHSP 1, forms homododecameric complexes under nondenaturing conditions and appears to be homologous to cytosolic class I small heat-shock proteins (smHSPs) from plant sources. In vitro evidence has been obtained that the isolated protein can function as a molecular chaperone: it increases, at stoichiometric levels, the renaturation yields of chemically denatured citrate synthase and also prevents the irreversible thermal inactivation of this enzyme. Although a role in desiccation tolerance has been hypothesized for seed smHSPs, this does not seem to be the case for Cs smHSP 1. We have investigated the presence of immunologically related proteins in orthodox and recalcitrant seeds of 13 woody species. Our results indicate that the presence of Cs smHSP 1-iike proteins, even at high levels, is not enough to confer desiccation tolerance, and that the amount of these proteins does not furnish a reliable criterion to identify desiccation-sensitive seeds. Additional proteins or mechanisms appear necessary to keep the viability of orthodox seeds upon shedding.

Plantation Forestry under Global Warming: Hybrid Poplars with Improved Thermotolerance Provide New Insights on the in Vivo Function of Small Heat Shock Protein Chaperones

“…CsHSP17.5, a major sHSP in chestnut trees, was overexpressed in hybrid poplar under the control of an enhanced CaMV 35S promoter. CsHSP17.5 exhibited several interesting features a priori, including the ability to improve cell viability under thermal stress in recombinant bacteria and the outstanding levels it normally reaches in chestnut stems and seeds (Collada et al, 1997;Soto et al, 1999;Lopez-Matas et al, 2004).…”

“…Third, it significantly improves Escherichia coli viability under heat stress conditions. Fourth, it accumulates at unusually high levels in both stems and seeds, where it reaches levels comparable to those of major storage proteins (Collada et al, 1997;Soto et al, 1999;Lopez-Matas et al, 2004). Besides suggesting a relevant role in thermotolerance, these features indicate that CsHSP17.5 can accumulate in vivo for long periods of time.…”

Effects of pre-sowing treatments on Jatropha curcas seed germination and seedling growth

“…(Green et al, 2013). The effect of this practice is not only to promote seed hydration but also to enhance the biosynthesis of stressresponse substances, like heat-shock proteins, which can play a role in the fast removal of inhibitors of seed germination (Collada et al, 1997;Bailly, 2004;Berjak and Pammenter, 2008). However, the right combination between treatment temperature, time and optimum temperature for germination, in the case of J. curcas, should be further investigated.…”

Molecular responses to thermal stress in woody plants

“…In woody plants such role was first demonstrated for a purified Castanea sativa (European chestnut) sHSP by Collada et al (1997). Afterwards, Soto et al (1999) found that overexpression of a chestnut protein in bacterial cells enhanced their tolerance to both high and low temperatures.…”