Elevated temperature and carbon dioxide effects on soybean seed composition and transcript abundance

Climate change due to increased [CO 2 ] and elevated temperature may impact the composition of crop seed. This study was conducted to determine the potential effects of climate change on composition and gene expression of soybean [Glycine max (L.) Merr. cv. 'Bragg'] seed. Soybean plants were grown in sunlit, controlled environment chambers under diel, sinusoidal temperatures of 28/18, 32/22, 36/26, 40/30, and 44/34°C (day/night, maximum/minimum), and two levels of [CO 2 ], 350 and 700 μmol mol -1 , imposed during the entire life cycle. The effect of temperature on mature seed composition and transcripts in developing seed was pronounced, but there was no effect of [CO 2 ]. Total oil concentration was highest at 32/22°C and decreased with further increase in temperature. Oleic acid concentration increased with increasing temperature whereas linolenic acid decreased. Concentrations of N and P increased with temperature to 40/30°C, then decreased. Total nonstructural carbohydrates (TNC) decreased as temperatures increased, and the proportion of soluble sugars to starch decreased. Transcripts of a gene that is downregulated by auxin (ADR12) were dramatically downregulated by elevated temperature, possibly reflecting the altered course of seed development under environmental stress. Transcripts of β-glucosidase, a gene expressed during normal soybean seed development, were detected in seed grown at 28/18°C but not in seed grown at 40/30°C, which also suggests that normal programs affecting seed composition were perturbed by elevated temperature. These results confirm previous studies indicating that high temperature alters soybean seed composition, and suggest possible mechanisms by which climate change may affect soybean seed development and composition.