Changes of proteins during dormancy and bud development of sweet cherry (Prunus avium L.)

Trees control the flowering processes in response to both environmental and endogenous (mechanisms at cellular/tissue level) conditions. Dormancy of flower buds is characterized by the reduction of growth and the enhancement of frost and desiccation resistance. The release of endodormancy and the beginning of ontogenetic development, as two important dates for developing reliable phenological models, escape from any visible signs. Thus, we identified - to our knowledge as first - relevant proteins in sweet cherry buds occurring during these phenological phases at high time resolution in three seasons (2012/13–2014/15) under natural conditions in Northeast Germany. The protein content of buds from the first week of October to leaf fall, from leaf fall to the end of endodormancy (t1), from t1 to the beginning of ontogenetic development (t1*), and from t1* until swollen bud, was comparable in each of the seasons. The increase of the protein content began after swollen bud and markedly differences occurred at side green, green tip, tight and open cluster. SDS gel electrophoresis followed by peptide mass fingerprinting accomplished by MALDI-TOF MS was applied for protein identification. ‘Volume intensity’ has been used to demonstrate the pattern and changes of proteins. None of the analysed proteins like for cell proliferation/differentiation (Phytosulfokines 3), carbon fixation (Rubisco), and defense against pathogenes (Major allergen Pru sv 1) indicates the date of endodormancy release or the beginning of the (invisible) ontogenetic development. The stages around green tip, tight, and open cluster resulted in markedly increase of the volume intensity of the protein for cell proliferation/differentiation and the carbon fixation, whereas the volume intensity of a protein for defense against pathogens markedly decreased. The pattern and changes of the volume intensity of neoxanthin synthase (NXS) in sweet cherry buds followed the increasing demand during endo- and ecodormancy to produce neoxanthin, which is a prominent member of the group of reactive oxygen species (ROS) scavengers.