Submitted to: Tree Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/10/2003
Publication Date: 1/2/2004
Citation: WISNIEWSKI, M.E., BASSETT, C.L., ARORA, R. DISTRIBUTION & PARTIAL CHARACTERIZATION OF SEASONALLY EXPRESS PROTEINS IN DIFFERENT AGED SHOOTS & ROOTS OF 'LORING' PEACH. TREE PHYSIOLOGY. Vol. 24, pgs. 339-345 January 2004. Interpretive Summary: The limited cold hardiness of peach trees results in major economic losses to fruit growers as a result of winter injury to trees, frost damage to open flowers, and increased levels of disease due to the presence of injured tissues. In order to improve cold hardiness, both a better understanding of how trees adapt to freezing temperatures and what proteins confer cold resistance are needed. In the current study, the accumulation of three seasonally-regulated proteins was monitored in bark tissues of different-aged shoots and roots of 'Loring' peach trees. Although the pattern and levels of accumulation of these proteins would suggest that they function in nitrogen storage, one of them appears to play a cryoprotective role, and another one is involved in disease resistance. They also accumulate to significantly different amounts in different aged tissues. Only one of the three proteins may play a role in nitrogen storage. The results indicate that a better understanding of protein function is needed before specific proteins are labeled as storage proteins. This information will be used to develop a more complete knowledge of the biochemical basis for cold hardiness in fruit trees. Future studies will focus on identifying the genes coding these proteins in order to better understand how these proteins are regulated.
Technical Abstract: By definition, proteins that accumulate in bark and xylem in large amounts in winter and are absent in summer are called storage proteins and are believed to serve as a vehicle for storing nitrogen reserves. These reserves are important for spring growth and helping trees to tolerate and/or recover from both abiotic and biotic stress. Based on seasonal patterns of accumulation we previously identified three proteins in bark tissues of peach (Prunus persica [L.] Batsch) that fall into this category. Little is known, however, about the distribution of these proteins in different-aged tissues or whether they have any function other than to act as a nitrogen reserve. The present study characterizes the seasonal distribution of a 60, 19, and 16 kDa protein in bark tissues of current-year, one-year-old shoots, scaffold branches, main trunks, and 4-5 year-old roots of 'Loring' peach. Verification of protein identity was based on molecular mass and reaction with antibodies directed against each specific protein. Distribution of the proteins was variable. For all three proteins, the greatest amount was present in mid-winter in current-year and one-year-old shoots. These tissues also showed the greatest seasonal variation in the amount of protein present. The 16 kDa protein was present only in the youngest shoots whereas the 19 kDa was present in all tissues examined. The 60 kDa protein was absent in root tissue. The 60 kDa protein has been identified as a dehydrin, and the 19 kDa protein appears to be related to a family of allergen proteins in Rosaceous plants, some members of which have also been identified as pathogenesis-related. The sequence obtained from the 16 kDa protein does not appear to have homology with any other proteins in the SwissProt database. Defining storage proteins solely by their pattern of accumulation and by the extent to which they accumulate may not be a good functional definition. It is possible that storage proteins may have functional roles other than just nitrogen storage.