Submitted to: Journal of Basic and Applied Sciences
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/5/2013
Publication Date: 3/13/2013
Publication URL: http://handle.nal.usda.gov/10113/57120
Citation: Lee, H., Garrett, W.M., Sullivan, J., Forseth, I., Natarajan, S.S. 2013. Differentially expressed proteins of soybean (Glycine max) pulvinus in light and dark conditions. Journal of Basic and Applied Sciences. 9:157-171. Interpretive Summary: Genetic modifications (GM) affecting specific tissues of the soybean plant have the potential to be important for providing nutritious and high quality soybean products. The pulvinus, a tissue at the base of leaves, allows leaves to move in response to the sun, which is important for maximizing light capture and avoiding light damage. We applied a modified extraction procedure to extract proteins from the soybean pulvinus and used modern proteomic techniques to elucidate the identity of proteins expressed in the pulvinus under light and dark conditions. We identified 11 pulvinus proteins that were present in higher amounts in the dark than in the light, and 7 proteins that decreased in the dark. This information is useful to scientists for understanding the physiology of the pulvinus as a basis for future modification using classical breeding or genetic modification, and provides researchers with a basis for determining protein changes that might occur in edible portions of the plant as a result of such modifications.
Technical Abstract: Soybean leaves (Glycine max) both track and avoid the sun through turgor changes of the pulvinus tissue at the base of leaves. Pulvinar response is known to be affected by both diurnally varying environmental factors and circadian patterns. Differential expression of the proteins between light and darkness are not well-known. In this study we used two-dimensional gel electrophoresis and mass spectrometry to separate and identify proteins in the soybean pulvinus that were differentially expressed in the light compared to a dark control. Out of 165 protein spots identified in our earlier study, 11 were found to have decreased expression in the light and 7 had increased light expression. The proteins that were more highly expressed in the light were mostly stress response proteins, while the under-expressed proteins were categorized as energy proteins. While the higher levels of expression of stress response proteins in the light align with other studies, the under-expressed light proteins require further examination to rule out artefactual results. These findings can provide a better understanding of the circadian pattern of protein expression in the legume pulvinus proteome.