Background: Soybean is a nutritionally important source of proteins and oils. Organspecific
analyses of the plants provided valuable information about physiological changes occurring
in particular organ. However, studies on the vegetative stage soybean during the growth and development
are lacking. Analyzing the growth stages of soybean at proteomic level is particularly important
for understanding the growth dynamics.
Objectives: The main objective of this study was to investigate the organ-specific growth pattern of
proteins during early growth stage.
Methods: Soybean (Glycine max L. cv Enrei) seeds were sown in each seedling case for 10 days and
roots, hypocotyls, and leaves were collected. Proteins were extracted and analyzed by nano-liquid
chromatography mass spectrometry. Mole percent abundance was calculated using emPAI values. To
determine the functional role of the proteins identified in the MS analysis, functional categorization
was performed using MapMan bin codes. Visualization of protein abundance ratio was performed
using MapMan software. Enzyme activity and quantitative reverse transcription-polymerase chain
reaction analyses were performed.
Results: A total of 357, 360, and 392 proteins were identified in root, hypocotyl, and leaf of vegetative
stage soybean, respectively. Proteins related to stress, cell organization, transport, signaling, and
mitochondrial electron transport chain decreased in root, hypocotyl, and leaf. Proteins related to protein
metabolism, glycolysis, and cell wall were comparable in root and hypocotyl; however, in leaf,
glycolysis and cell wall related proteins were decreased. Aldehyde dehydrogenase was decreased in
abundance and activity in hypocotyl and leaf as compared to root. Major latex proteins 43 and 423
changed in abundance in an organ-specific manner. The mRNA expression level of major latex proteins
exhibited a differential expression in the hypocotyl of soybean during flooding stress and recovery.
Conclusion: Our results suggest that aldehyde dehydrogenase and major latex proteins play key roles
in growth of soybean in an organ-specific way.