Molecular Biology and Biotechnology, CSIR-National Botanical Research Institute (CSIR-NBRI), Council of Scientific and Industrial Research (CSIR-NBRI), Rana Pratap Marg, Lucknow 226001, India.
Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
Plant Physiol. 2024 Oct 1;196(2):1426-1443. doi: 10.1093/plphys/kiae400.
Tomato (Solanum lycopersicum L.) is rich in nutrients and has been an important target for enhancing the accumulation of various metabolites. Tomato also contains cholesterol-derived molecules, steroidal glycoalkaloids (SGAs), which contribute to pathogen defense but are toxic to humans and considered antinutritional compounds. Previous studies suggest the role of various transcription factors in SGA biosynthesis; however, the role of light and associated regulatory factors has not been studied in tomatoes. Here, we demonstrated that SGA biosynthesis is regulated by light through the ELONGATED HYPOCOTYL 5 homolog, SlHY5, by binding to light-responsive G-boxes present in the promoters of structural and regulatory genes. SlHY5 complemented Arabidopsis (Arabidopsis thaliana) and tobacco (Nicotiana tabacum) hy5 mutants at molecular, morphological, and biochemical levels. CRISPR/Cas9-based knockout tomato plants, SlHY5CR, showed downregulation of SGA and phenylpropanoid pathway genes, leading to a significant reduction in SGA (α-tomatine and dehydrotomatine) and flavonol contents, whereas plants overexpressing SlHY5 (SlHY5OX) showed the opposite effect. Enhanced SGA and flavonol levels in SlHY5OX lines provided tolerance against Alternaria solani fungus, while SlHY5CR lines were susceptible to the pathogen. This study advances our understanding of the HY5-dependent light-regulated biosynthesis of SGAs and flavonoids and their role in biotic stress in tomatoes.
番茄（Solanum lycopersicum L.）富含营养，一直是增强各种代谢物积累的重要目标。番茄还含有胆固醇衍生的分子，甾体糖苷生物碱（SGAs），它们有助于抵御病原体，但对人类有毒，被认为是抗营养化合物。先前的研究表明，各种转录因子在 SGA 生物合成中起作用；然而，番茄中尚未研究过光及其相关调节因子的作用。在这里，我们通过结合结构和调节基因启动子中存在的光反应 G-盒，证明了光通过伸长的下胚轴 5 同源物 SlHY5 调节 SGA 生物合成。SlHY5 在分子、形态和生化水平上补充了拟南芥（Arabidopsis thaliana）和烟草（Nicotiana tabacum）hy5 突变体。基于 CRISPR/Cas9 的番茄 SlHY5CR 敲除植物表现出 SGA 和苯丙素途径基因下调，导致 SGA（α-茄碱和脱氢茄碱）和类黄酮含量显著降低，而过量表达 SlHY5 的植物（SlHY5OX）则表现出相反的效果。SlHY5OX 系中增强的 SGA 和类黄酮水平为番茄提供了对Alternaria solani 真菌的耐受性，而 SlHY5CR 系则易受病原体感染。这项研究推进了我们对 HY5 依赖的光调控 SGA 和类黄酮生物合成及其在番茄生物胁迫中的作用的理解。
