Learning from nature: phytochemical strategies to protect against UV-B damage
Mustafa Bulut, Takayuki Tohge, Wei Chen, Jie Luo, Zhirong Wang, Xu Huang, Meiliang Zhou, Alisdair R. Fernie
Abstract
The colonization of terrestrial ecosystems exposed plants to intensified solar radiation, particularly that of UV-B (280-315 nm), which induces DNA, RNA and protein damage. While historical ozone depletion exacerbated UV-B stress, recent stabilization efforts have mitigated its effects. However, independent fluctuations in UV-B levels continue to challenge crop performance, particularly in equatorial regions. Plants have evolved diverse UV-B-protective strategies, including producing specialized metabolites such as flavonoids, phenylpropanoids and ascorbate alongside lineage-specific compounds like mycosporine-like amino acids. These metabolites act as antioxidants, UV-B absorbers and stress mitigators, with their diversity driven by gene duplication and environmental adaptation. In keeping with this, genome-wide association studies (GWAS) have identified key genetic loci, such as OsUVR8 and OsMYB44, regulating UV-B tolerance through enhanced flavonol glycoside and tryptamine derivatives biosynthesis. These combined data suggest that we should be able to fortify plants' tolerance to UV-B by future breeding strategies. Advances in spatially resolved metabolomics and machine learning hold promise for identifying novel UV-B-protective compounds and facilitating precise metabolic engineering. In addition, modifications to cell wall composition, including lignin thickening and embedding UV-B-absorbing phenylpropanoids, offer another venue for protective mechanisms. Recent discoveries of natural variation in UV-B protectants across species like rice, barley and maize highlight the potential for breeding UV-resilient crops. Such innovations will not only bolster UV-B tolerance but also enhance crop nutritional value, as many UV-B-protective compounds also serve as essential nutrients as well as harbor antioxidant properties. This comprehensive understanding of UV-B responses, from molecular signaling to phytochemical strategies and structural adaptations, underscores the potential for leveraging genetic engineering and natural variation to mitigate UV-B-induced stress.