The impact of solar UV radiation on the proteome in three soybean lines differing in flavonoid content

Even though a substantial number of studies have evaluated the response of plants to changing levels of solar ultraviolet-B radiation (UV-B between 280 and 320 nm), relatively few have investigated these responses at the proteome level. In this study, two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) was used to systematically investigate the impact of solar ultraviolet-B (UV-B) radiation on the soybean (Glycine max) leaf proteome. In order to investigate the protective role of flavonoids against UV-B, two isolines of the Clark cultivar (the standard line with moderate levels of flavonoids and the magenta line with reduced flavonoids) were grown in the field with or without natural levels of UV-B. The first trifoliate leaf was harvested after days for proteome analysis. More than 300 protein spots were reproducibly resolved and detected on each gel. Statistical analysis showed that 67 protein spots were significantly (P < 0.05) altered by ambient UV-B, compared to the controls. The effects on the magenta line were magnified and the direction of the response varied among the proteins identified. Twelve protein spots were not altered by UV-B but showed significantly (P < 0.05) different accumulations between the two lines. The proteins altered by UV-B exposure were quite diverse and were involved in metabolism, energy, protein destination/storage, protein synthesis, disease/defense, transcription, and secondary metabolism. These results indicate that ambient levels of UV-B may provide a key regulatory signal for an array of plant biochemical and physiological processes.