| Abstract: | In several plant species, certain cold-regulated proteins share unique properties. These proteins are (a) heat stable and (b) hydrophilic and are related to the Group 2 late embryogenesis abundant or dehydrin family of proteins. Our previous work with sibling deciduous and evergreen peach genotypes demonstrated a correlation between the level of accumulation of certain bark proteins and cold-acclimation potential of these tissues. Here we identify a 60-kD bark protein in peach (Prunus persica L.] Batsch), PCA60 ("peach cold acclimation"), that is accumulated during cold acclimation and is heat stable. Immunological studies indicated that this protein is related to the dehydrin family of proteins and accumulates at much higher levels in the bark tissues of the deciduous genotype than in the evergreen. Amino acid composition indicated that the 60-kD protein has a compositional bias for glycine (24%), glutamic acid/glutamine (11.4%), aspartic acid/asparagine (10%), and threonine (9.6%), contains relatively low levels of aromatic amino acids (phenylalanine and tyrosine), and is rich in hydrophilic amino acids. A novel characteristic of the 60-kD cold-acclimation protein is the presence of a repeating nine-amino acid sequence. A five-amino acid stretch, which is included within this repeating motif, shares striking homology with other cold-regulated proteins and dehydrins. |
