ITRAQ-based comparative proteomic analysis of embryogenic and non-embryogenic tissues of Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr)

Abstract

Prince Rupprecht’s larch (Larix principis-rupprechtii Mayr) is an important native coniferous tree species with major ecological and commercial value in China. In larch, somatic embryogenesis (SE) occurs commonly employing immature zygotic embryos as explants through an indirect process beginning with the formation of embryogenic tissue on the auxin-rich medium and further development of embryos. During the induction stage, we observed embryogenic callus (EC) and non-embryogenic callus (NEC) sharing the same origin arise in the presence of both 2,4-D and 6-BA. Visual and histological observation indicated that EC and NEC possess distinctly different appearances and structures. However, the precise molecular mechanisms during SE induction in larch were unclear, and a comparative proteomic analysis of EC and NEC was performed to examine somatic embryogenic-specific proteins. Isobaric tags for relative and absolute quantitation combined with LC–MS/MS were employed to detect differences between EC and NEC proteomes. In total, 503 proteins were detected, revealing 71 differentially expressed proteins. Obtained proteins were further analyzed to determine their potential functions in the induction of SE. Several proteins involved in the development metabolic processes, such as ADP-ribosylation factor GTPase-activating proteins, triosephosphate isomerase, and proliferating cell nuclear antigen, were significantly upregulated in EC, indicating candidate protein markers of SE in larch. The results provide new insights on the characterization and understanding SE at the proteome level.