Shan Xiaotong, Li Yueqing, Yang Song, Yang Zhongzhou, Qiu Meng, Gao Ruifang, Han Taotao, Meng Xiangyu, Xu Zhengyi, Wang Li, Gao Xiang
Key Laboratory of Molecular Epigenetics of MOE and Institute of Genetics & Cytology, Northeast Normal University, Changchun, 130024, China.
New Phytol. 2020 Dec;228(6):1864-1879. doi: 10.1111/nph.16818. Epub 2020 Aug 18.
Floral flavonols play specific pivotal roles in pollinator attraction, pollen germination and fertility, in addition to other functions in vegetative organs. For many plants, the process of flavonol biosynthesis in late flower development stages and in mature flower tissues is poorly understood, in contrast to early flower development stages. It is thought that this process may be regulated independently of subgroup 7 R2R3 MYB (SG7 MYB) transcription factors. In this study, two FLS genes were shown to be expressed synchronously with the flower development-specific and tissue-specific biosynthesis of flavonols in Freesia hybrida. FhFLS1 contributed to flavonol biosynthesis in early flower buds, toruses and calyxes, and was regulated by four well-known SG7 MYB proteins, designated as FhMYBFs, with at least partial regulatory redundancy. FhFLS2 accounted for flavonols in late developed flowers and in the petals, stamens and pistils, and was targeted directly by non SG7 MYB protein FhMYB21L2. In parallel, AtMYB21 and AtMYB24 also activated AtFLS1, a gene highly expressed in Arabidopsis anthers and pollen, indicating the conserved regulatory roles of MYB21 against FLS genes in these two evolutionarily divergent angiosperm plants. Our results reveal a novel regulatory and synthetic mechanism underlying flavonol biosynthesis in floral organs and tissues which may be exploited to investigate supplementary roles of flavonols in flowers.
除了在营养器官中发挥其他功能外，花中的黄酮醇在吸引传粉者、花粉萌发和育性方面发挥着特定的关键作用。与花发育早期阶段相比，许多植物在花发育后期阶段和成熟花组织中的黄酮醇生物合成过程仍知之甚少。据认为，这一过程可能独立于第7亚组R2R3 MYB（SG7 MYB）转录因子进行调控。在本研究中，两个FLS基因被证明与小苍兰中黄酮醇的花发育特异性和组织特异性生物合成同步表达。FhFLS1有助于早期花芽、花托和花萼中的黄酮醇生物合成，并受四种著名的SG7 MYB蛋白（称为FhMYBFs）调控，且至少存在部分调控冗余。FhFLS2负责发育后期花朵以及花瓣、雄蕊和雌蕊中的黄酮醇合成，并直接受非SG7 MYB蛋白FhMYB21L2的靶向作用。同时，AtMYB21和AtMYB24也激活了AtFLS1，该基因在拟南芥花药和花粉中高表达，表明MYB21对这两种进化上不同的被子植物中的FLS基因具有保守的调控作用。我们的研究结果揭示了花器官和组织中黄酮醇生物合成的一种新的调控和合成机制，这可能有助于研究黄酮醇在花中的补充作用。
