The role of light in soybean seed filling metabolism
Article first published online: 27 JAN 2009
© 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd
The Plant Journal
Volume 58, Issue 2, pages 220–234, April 2009
How to Cite
Allen, D. K., Ohlrogge, J. B. and Shachar-Hill, Y. (2009), The role of light in soybean seed filling metabolism. The Plant Journal, 58: 220–234. doi: 10.1111/j.1365-313X.2008.03771.x
- Issue published online: 8 APR 2009
- Article first published online: 27 JAN 2009
- Received 29 October 2008; revised 18 November 2008; accepted 27 November 2008; published online 27 January 2009.
- seed metabolism;
- redox balance;
- isotopic labeling;
- metabolic flux analysis;
- soybean embryo;
Soybean (Glycine max) yields high levels of both protein and oil, making it one of the most versatile and important crops in the world. Light has been implicated in the physiology of developing green seeds including soybeans but its roles are not quantitatively understood. We have determined the light levels reaching growing soybean embryos under field conditions and report detailed redox and energy balance analyses for them. Direct flux measurements and labeling patterns for multiple labeling experiments including [U-13C6]-glucose, [U-13C5]-glutamine, the combination of [U-14C12]-sucrose + [U-14C6]-glucose + [U-14C5]-glutamine + [U-14C4]-asparagine, or 14CO2 labeling were performed at different light levels to give further insight into green embryo metabolism during seed filling and to develop and validate a flux map. Labeling patterns (protein amino acids, triacylglycerol fatty acids, starch, cell wall, protein glycan monomers, organic acids), uptake fluxes (glutamine, asparagine, sucrose, glucose), fluxes to biomass (protein amino acids, oil), and respiratory fluxes (CO2, O2) were established by a combination of gas chromatography-mass spectrometry, 13C- and 1H-NMR, scintillation counting, HPLC, gas chromatography-flame ionization detection, C:N and amino acid analyses, and infrared gas analysis, yielding over 750 measurements of metabolism. Our results show: (i) that developing soybeans receive low but significant light levels that influence growth and metabolism; (ii) a role for light in generating ATP but not net reductant during seed filling; (iii) that flux through Rubisco contributes to carbon conversion efficiency through generation of 3-phosphoglycerate; and (iv) a larger contribution of amino acid carbon to fatty acid synthesis than in other oilseeds analyzed to date.