Proteomic evaluation of the response of soybean (Glycine max var Seoritae) leaves to UV-B

UV-B radiation plays an important role in photomorphogenesis; however, excessive UV-B radiation decreases photosynthesis and causes damage to cellular DNA. In the present study, two different light sources (UV-B and natural light) were applied to 18 day-old young soybean plants (Glycine max Merr. var Seoritae), after which the plants were harvested and their pigment contents, chlorophyll fluorescence, and proteomic changes investigated. The contents of carotenoids and anthocyanins increased significantly in response to excessive UV-B radiation. Additionally, several proteins such as ATP synthase, sedoheptulose-1,7-bisphosphatase, transketolase, peroxiredoxins and oxygen-evolving enhancer proteins were up-regulated in soybean leaves exposed to excessive UV-B. Alanine-2-oxoglutarate aminotransferase 1, aldolase, gamma-glutamyl hydrolase, and 28 kDa stem glycoprotein were down-regulated in soybean leaves exposed to excessive UV-B. Excessive UV-B light also led to a dramatic reduction in photosynthetic efficiency when compared to controls by causing irreversible damage to PSII determined by a fluorescence imaging system. With the treatment of natural illumination, the contents of carotenoids and anthocyanains were not changed in the leaves and the photosynthetic ability in the natural light was retained. These findings indicate that Seoritae soybean leaves might protect themselves from excessive UV-B radiation via up-regulation of antioxidative proteins and antioxidant pigments.