Distribution of Seasonally Expressed Storage Proteins in Different-aged Shoots and Roots of `Loring' Peach

Abstract

During autumnal leaf senescence, leaf nitrogen is translocated to other sites for storage, especially bark tissues. By definition, proteins that accumulate in large amounts in winter and are absent in summer are called storage proteins. Previously, we have characterized three proteins in peach bark tissues 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, 1-year-old, scaffold, and trunk bark, and 4- to 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. The greatest amount of all three proteins was present in current-year and 1-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 16-kDa protein appears to be related to defensins. The identity of the 19-kDa protein has not been confirmed. The amino acid composition of the three proteins will be presented and the implications of these results on management practices will be discussed.