Analysis of differentially accumulated proteins associated with graft union formation in pecan (Carya illinoensis)

Grafting is of particular importance for the mass cultivation of pecan (Carla illinoensis), which can greatly shorten the long juvenile phase of this species. To reveal the molecular mechanism underlying graft union formation, the dynamic proteome changes at the graft union were investigated 0, 3, 8, 15, and 30 days after grafting in homograft of pecan by two-dimensional gel electrophoresis. Forty-nine protein spots that showed more than two-fold difference in their values were positively identified by mass spectrometry. These identified proteins were associated with energy metabolism, stress and defense responses, protein metabolism, amino acid and nucleotide metabolism, secondary metabolism, hormone related, cell cytoskeleton, and function unknown. Among the proteins, ascorbate peroxidase and peroxiredoxin could scavenge the excess reactive oxygen species induced by wounding, which might play an important role in the graft process. 1-aminocyclopropane-1-car-boxylic acid oxidase probably led to ethylene biosynthesis at the graft interface, participating in the wound response during the early stage of grafting. 30S ribosomal protein seemed to support callus proliferation through promoting the synthesis of proteins. Alpha tubulin and metacaspase might be involved in the differentiation of tracheary elements during graft-union formation. Analysis of the identified proteins will provide insights into the molecular mechanism of graft union formation.