posted on 2020-09-04, 12:34authored byLauren Fedenia, Robert R. Klein, Linda Dykes, William L. Rooney, Patricia E. Klein
Black sorghum [Sorghum bicolor (L.) Moench] is
characterized by the black appearance of the pericarp and production
of 3-deoxyanthocyanidins (3-DOA), which are valued for their cytotoxicity
to cancer cells and as natural food colorants and antioxidant additives.
The black pericarp phenotype is not fully penetrant in all environments,
which implicates the light spectrum and/or photoperiod as the critical
factor for trait expression. In this study, black- or red-pericarp
genotypes were grown under regimes of visible light, visible light
supplemented with UVA or supplemented with UVA plus UVB (or dark control).
Pericarp 3-DOAs and pericarp pigmentation were maximized in the black
genotype exposed to a light regime supplemented with UVB. Changes
in gene expression during black pericarp development revealed that
ultraviolet light activates genes related to plant defense, reactive
oxygen species, and secondary metabolism, suggesting that 3-DOA accumulation
is associated with activation of flavonoid biosynthesis and several
overlapping defense and stress signaling pathways.