Learning from nature: phytochemical strategies to protect against UV-B damage

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.