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Abstract：
Flavonol synthase gene (FLS) is a member of the 2-oxoglutarate-dependent dioxygenase (2-ODD) superfamily and plays an important role in plant flavonoids biosynthetic pathways. Safflower (Carthamus tinctorius L.), a key source of traditional Chinese medicine, is widely cultivated in China. Although the flavonoid biosynthetic pathway has been studied in several model species, it still remains to be explored in safflower. In this study, we aimed to elucidate the role of CtFLS1 gene in flavonoid biosynthesis and drought stress responses. The bioinformatics analysis on the CtFLS1 gene showed that it contains two FLS-specific motifs (PxxxIRxxxEQP and SxxTxLVP), suggesting its independent evolution. Further, the expression level of CtFLS1 in safflower showed a positive correlation with the accumulation level of total flavonoid content in four different flowering stages. In addition, CtFLS1-overexpression (OE) Arabidopsis plants significantly induced the expression levels of key genes involved in flavonol pathway. On the contrary, the expression of anthocyanin pathway-related genes and MYB transcription factors showed down-regulation. Furthermore, CtFLS1-OE plants promoted seed germination, as well as resistance to osmotic pressure and drought, and reduced sensitivity to ABA compared to mutant and wild-type plants. Moreover, CtFLS1 and CtANS1 were both subcellularly located at the cell membrane and nucleus; the yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assay showed that they interacted with each other at the cell membrane. Altogether, these findings suggest the positive role of CtFLS1 in alleviating drought stress by stimulating flavonols and anthocyanin accumulation in safflower.
摘要：
黄酮醇合成酶基因（FLS）是2-氧戊二酸依赖性双加氧酶（2-ODD）超家族的成员，在植物类黄酮生物合成途径中起着重要作用。红花（红花L.），中药的关键来源，在中国广泛种植。虽然类黄酮生物合成途径已经在几个模型物种中进行了研究，在红花中仍有待探索。在这项研究中,我们旨在阐明CtFLS1基因在类黄酮生物合成和干旱胁迫响应中的作用。对CtFLS1基因的生物信息学分析表明，它含有两个FLS特异性基序(PxxxIRxxxEQP和SxxTxLVP)，表明它的独立进化。Further,红花中CtFLS1的表达水平与4个不同开花期总黄酮含量的积累水平呈正相关。此外,CtFLS1过表达（OE）拟南芥植物显着诱导了黄酮醇途径中关键基因的表达水平。相反,花青素途径相关基因和MYB转录因子表达下调。此外，CtFLS1-OE植物促进种子萌发，以及对渗透压和干旱的抵抗力，与突变体和野生型植物相比，对ABA的敏感性降低。此外，CtFLS1和CtANS1均位于细胞膜和细胞核的亚细胞内；酵母双杂交和双分子荧光互补（BiFC）分析表明，它们在细胞膜上相互作用。总之,这些发现表明CtFLS1通过刺激红花中黄酮醇和花色苷的积累在缓解干旱胁迫中的积极作用。
