Genetic and Transcriptomic Variation in Response of Soybean to Enhanced Ultraviolet-B Irradiation

The depletion of the ozone layer in stratosphere has led to periodic but unpredictable spike in UV-B intensity as well as increased UV-B light levels. Therefore, it is incredibly necessary to elucidate defense responses of soybean (Glycine max [L.]) to UV-B stress for UV-B resistant variety development. In this study, a total of 140 genotypes, including 94 G. max and 46 Glycine soja accessions, were first evaluated for their sensitivity to supplemental UV-B irradiation, resulting in identifying the most UV-B resistant (Buseok) and sensitive (Cheongja3) G. max genotypes. Using these two soybean genotypes, we provided a more comprehensive report about both genetic and transcriptomic variation in the response to enhanced UV-B exposure. We surveyed UV-B-related genes in soybean by performing homology searches using Arabidopsis genes previously reported to be involved in UV-B response. Sequence variations within and/or near the UV-B-related genes were then identified at the whole-genome level between two genotypes, including non-synonymous ones in four genes related to UV-B photomorphogenesis. Furthermore, transcriptomic comparison between two genotypes exposed to high UV-B fluences revealed that UV-B resistant Buseok provoked the defense mechanisms against UV-B stress through the phosphatidic acid-dependent signaling pathways via phospholipase C/DGK enzymes and also operated cell death and immunity systems.