Proteomic Analysis of Germinating Soybean Hypocotyl Using Quadrupole Orbitrap Mass Spectrometer

During seed germination, hypocotyl was first elongated, and then pushed the 2 cotyledons above ground. To determine protein profiles of soybeans hypocotyl under initiation of seed germination, total proteins extracted from the pith, vascular bundle, and cortex of 6-hour-imbibition hypocotyl dissected by Zeiss PALM MicroBeam LCM system were identified by quadrupole Orbitrap (Q Exactive) mass spectrometer. In total, 1697, 2091, and 2938 proteins from cortex, pith, and vascular bundle were mapped to published soybean genome sequence, respectively. Our results suggested that most LEA proteins highly accumulated in hypocotyl. This observation confirmed the results of in situ hybridization in previous study (Shih et al., 2010). On the other hand, numerous of chaperonins and transporters were also identified. These results suggested that most transporters were present in hypocotyl during seed development. Their structures and functions might be protected by stress-related proteins, such as LEA, and chaperonins. To conclude, most abundant proteins in hypocotyl during early germination stage were stress-related proteins and chaperonins. They might play important roles in maintenance germination process.