Protein Cryoprotective Activity of a Cytosolic Small Heat Shock Protein That Accumulates Constitutively in Chestnut Stems and Is Up-Regulated by Low and High Temperatures

摘要: Heat shock, and other stresses that cause protein misfolding aggregation, trigger the accumulation of heat shock proteins (HSPs) in virtually all organisms. Among HSPs higher plants, those belonging to small HSP (sHSP) family remain least characterized functional terms. We analyzed occurrence sHSPs vegetative organs Castanea sativa (sweet chestnut), a temperate woody species exhibits remarkable freezing tolerance. A constitutive sHSP subject seasonal periodic changes abundance was immunodetected stems. This identified by matrix-assisted laser-desorption ionization time flight mass spectrometry internal peptide sequencing as CsHSP17.5, cytosolic class I previously described cotyledons. Expression corresponding gene stems confirmed through cDNA cloning reverse transcription-PCR. Stem mRNA profiles indicated CsHSP17.5 is significantly up-regulated spring fall, reaching maximal levels late summer and, especially, winter. In addition, cold exposure found quickly activate shsp expression both roots chestnut seedlings kept growth chambers. Our main finding purified very effective protecting cold-labile enzyme lactate dehydrogenase from freeze-induced inactivation (on molar basis, about 400 times more cryoprotectant than hen egg-white lysozyme). Consistent with these observations, repeated freezing/thawing did not affect appreciably chaperone activity diluted nor its ability form dodecameric complexes vitro. Taken together, results substantiate hypothesis can play relevant roles acquisition