Identification and analysis of differentially expressed proteins during cotyledon embryo stage in longan

The cotyledon stage is a crucial developmental stage during longan embryo development. Two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization-time of flight-tandem mass spectrometry (MALDI-TOF/TOF-MS) were conducted to separate and identify proteins expressed in the longan cotyledon embryos at different development stages. A total of 28 proteins that exhibited regulated expression were successfully identified with a protein identification success rate of 72.2%. The 28 proteins were assigned to six functional classes based on their putative biological functions: energy and metabolism (21%), secondary metabolism (18%), protein metabolism (21%), cell division (11%), antioxidation (4%), nucleic acid metabolism (4%), hormonal regulation (4%) and unknown proteins (18%). Interestingly, three enzymes involved in flavonoid biosynthesis, whose expression in embryos had not been observed previously were clearly up-regulated during the cotyledon stage of embryo development in longan. Identification and analysis of the 28 proteins would shed new lights on further understanding of the biochemical and physiological processes of the embryo development at cotyledon stage in longan.

Research highlights▶ We firstly used two-dimensional electrophoresis and matrix-assisted laser desorption ionization-time of flight-tandem mass spectrometry to separate and identify proteins expressed in the longan cotyledon embryos at different development stages. ▶ A total of 28 proteins that exhibited regulated expression were successfully identified. ▶ We find three enzymes involved in flavonoid biosynthesis, whose expression in embryos had not been observed previously were clearly up-regulated during the cotyledon stage of embryo development in longan. ▶ Identification and analysis of the proteins provide new leads to further understanding the biochemical and physiological processes of leading to the cotyledon stage of embryo development in longan.