Selection of housekeeping genes for gene expression studies on the development of fruit bearing shoots in Chinese jujube (Ziziphus jujube Mill.).

Chinese jujube (Ziziphus jujube Mill.) is important economically for its fruit and also bears attractive medical value. Its flower development concurs with the growth of current fruit bearing shoots (FBSs). However, events involved in current FBSs, including FBS differentiation, flower development, and reliable housekeeping gene are still unknown. In this study, the morphology of FBS development and floral formation were examined and expression profiles of several potential internal control genes was determined. These included genes encoding proteins involved in protein translation (translation elongation factor 1alpha, ZjEF1), protein folding (cyclophilin, ZjCyP) or degradation (ubiquitin extension protein, ZjUBQ), and proteins involved in the structure of the cytoskeleton (beta-actin, ZjACT) or nucleosome (histone3, ZjH3). Our results showed that the floral development in early growing FBSs (less than 20 mm in length) or shoot apices was not complete. Among ZjACT, ZjEF1, ZjCyP, ZjUBQ, and ZjH3, ZjH3 was the most suitable housekeeping gene to evaluate FBS development, based on their expression in early growing FBSs, shoot apices, and different organs. These results will be useful for further molecular mechanism study about FBS development in Chinese jujube.