Influence of graft incompatibility on gene expression and enzymatic activity of UDP-glucose pyrophosphorylase

Graft compatibility response is a complex mechanism with a wide range of different physiological, biochemical, and anatomical interactions. However, little is known about the biochemical basis for incompatibility and the molecular mechanism involved in this response. In the present paper, the influence of grafting on the protein pattern in the incompatible heterograft combination of apricot (Prunus armeniaca L. cv. Moniqui) on plum (Prunus cerasifera × Prunus munsoniana cv. Marianna 2624) and their homograft combinations using callus fusion in vitro was investigated. A decrease in a 55 kDa protein band at the stock of the incompatible union was observed during the 2 weeks after grafting. Using SDS-PAGE combined with MALDI-TOF, this protein was identified as an UDP-glucose pyrophosphorylase (UGPase) with a high homology to other higher plants. In addition, the UGPase mRNA transcript and enzyme activity were also diminished in the stock from the incompatible combination at 10 DAG. Furthermore, genotypic differences in UGPase activity were observed between the apricot cultivar 'Moniqui' and the plum rootstock 'Marianna 2624'. These results suggested that this protein could be related to the graft compatibility/incompatibility responses.