Annual patterns of total soluble sugars and proteins related to cold-hardiness in olive (Olea europaea L. 'Gemlik')

Abstract

Annual patterns of cold hardiness, total soluble sugars (TSS) and proteins (TSP) were characterised during two consecutive years (May 2003-April 2005) in leaf and bark tissues of olive (Olea europaea L.) 'Gemlik' trees. One-year-old shoots from 13-year-old olive trees were collected each month and exposed to low temperature at 4 degrees C, -5 degrees C, -10 degrees C, or -20 degrees C for 12 h to determine their cold-hardiness (LT50; assessed by electrolyte leakage). A considerable increase in cold-hardiness was observed with decreasing temperature. Leaf and bark tissues exhibited an increase in cold-hardiness during the Autumn, which reached a maximum in mid-Winter, then gradually decreased during the Spring, and reached a minimum in mid-Summer. Results indicated that leaf and bark tissues in both experimental years responded similarly to cold, with a continuous increase in their TSS and TSP contents during field adaptation in Autumn and Winter, which paralleled their cold-hardiness. The annual cycle of TSP from leaf and bark tissue was characterised by one dimensional SDS-PAGE. A seasonal fluctuation was observed in leaf proteins of 66 kDa and 43 kDa, and in bark proteins of 70 kDa, 43 kDa and 16 kDa, which paralleled cold-acclimation. Evaluation of these leaf and bark TSP profiles showed that these polypeptides disappeared in the Summer, followed by their accumulation again during the Autumn and Winter. Moreover, all these polypeptides became less visible during the Spring. The relationships between these five proteins, TSS contents, and cold-hardiness in olive are discussed.