Immunolocalization and in Vitro Cryoprotective Activity of PCA60: A Peach Dehydrin

Abstract

<jats:p>Cold acclimation in temperate, woody plants is a complex phenomenon that involves distinct changes in gene activity and protein synthesis. In previous research, a 60-kDa protein (PCA60), belonging to the dehydrin family of stress-related proteins, was identified in peach bark, and its corresponding gene (<jats:italic>ppdhn1</jats:italic>) was cloned and characterized. Presently, we report on the results of immunolocalization studies and in vitro cryoprotection assays. Seasonal collections of current-year stems were embedded in LR White or epoxy resin and sections of bark were probed with either a polyclonal antibody directed against a 15 amino acid sequence consensus region of dehydrins or a polyclonal antibody directed against partially-purified PCA60. In vitro cryoprotection assays utilized lactose dehydrogenase (LDH), a cold-labile enzyme. Immunolocalization at the light level indicated that the dehydrin was confined to the cytoplasm and absent in organelles. This localization was preliminarily confirmed at the ultrastructural level. LDH assays indicated cryoprotective activity in total protein extracts collected from winter bark tissues but completely absent in extracts of summer bark tissues. Preliminary LDH assays utilizing purified PCA60 also demonstrated cryoprotective activity. In general, the data further support a role for dehydrins in cold acclimation of woody plants.</jats:p>

Additional freeze hardiness in wheat acquired by exposure to −3 °C is associated with extensive physiological, morphological, and molecular changes

“…It appears that these cold-induced proteins are either isoforms that have antifreeze activity or are post-translationally converted to have antifreeze activity (Thomashow, 1999). Other proteins, such as peach dehydrin (PCA 60) and thaumatin-like protein (AHCSP 33) from peanut, evidently have both antifreeze and cryoprotective activity (Wisniewski, 1997;Dave and Mitra, 1998). In addition, a novel antifreeze protein, with a leucine-rich repeat, has been purified and characterized from carrots (Worrall et al, 1998;Smallwood et al, 1999).…”