Phenotypic, Phytochemical, and Transcriptomic Analysis of Black Sorghum (Sorghum bicolor L.) Pericarp in Response to Light Quality

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.

黑高粱[Sorghum bicolor (L.) Moench]以果皮呈黑色且可合成3-脱氧花青素（3-deoxyanthocyanidins，3-DOA）为典型特征；该物质因对癌细胞具有细胞毒性、可作为天然食品着色剂及抗氧化添加剂而备受重视。黑色果皮表型并非在所有环境中均完全外显，这表明光谱和/或光周期是调控该性状表达的关键因素。本研究将黑果皮或红果皮基因型高粱分别种植于四种光照处理方案下：纯可见光、可见光补充UVA、可见光补充UVA与UVB，以及黑暗对照组。实验结果显示，在经UVB补充光照的黑果皮基因型材料中，果皮内3-脱氧花青素含量与果皮着色程度均达到峰值。对黑果皮发育过程中的基因表达变化进行分析后发现，紫外线可激活与植物防御、活性氧代谢及次生代谢相关的基因，这提示3-脱氧花青素的积累与类黄酮生物合成通路以及多个重叠的防御与应激信号通路的激活密切相关。