Sun Heng, Song Heyun, Deng Xianbao, Liu Juan, Yang Dong, Zhang Minghua, Wang Yuxin, Xin Jia, Chen Lin, Liu Yanling, Yang Mei
Aquatic Plant Research Center, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China.
Hubei Key Laboratory of Wetland Evolution and Ecological Restoration, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China.
Front Plant Sci. 2022 May 23;13:885503. doi: 10.3389/fpls.2022.885503. eCollection 2022.
Lotus plumule is a green tissue in the middle of seeds that predominantly accumulates bisbenzylisoquinoline alkaloids (bis-BIAs) and chlorophyll (Chl). However, the biosynthetic mechanisms of these two metabolites remain largely unknown in lotus. This study used physiological and RNA sequencing (RNA-Seq) approaches to characterize the development and molecular mechanisms of bis-BIAs and Chl biosynthesis in lotus plumule. Physiological analysis revealed that exponential plumule growth occurred between 9 and 15 days after pollination (DAP), which coincided with the onset of bis-BIAs biosynthesis and its subsequent rapid accumulation. Transcriptome analysis of lotus plumule identified a total of 8,725 differentially expressed genes (DEGs), representing ~27.7% of all transcripts in the lotus genome. Sixteen structural DEGs, potentially associated with bis-BIAs biosynthesis, were identified. Of these, 12 encoded -methyltransferases (OMTs) are likely involved in the methylation and bis-BIAs diversity in lotus. In addition, functionally divergent paralogous and redundant homologous gene members of the BIAs biosynthesis pathway, as well as transcription factors co-expressed with bis-BIAs and Chl biosynthesis genes, were identified. Twenty-two genes encoding 16 conserved enzymes of the Chl biosynthesis pathway were identified, with the majority being significantly upregulated by Chl biosynthesis. Photosynthesis and Chl biosynthesis pathways were simultaneously activated during lotus plumule development. Moreover, our results showed that light-driven Pchlide reduction is essential for Chl biosynthesis in the lotus plumule. These results will be useful for enhancing our understanding of alkaloids and Chl biosynthesis in plants.
莲胚芽是种子中部的绿色组织，主要积累双苄基异喹啉生物碱（双BIAs）和叶绿素（Chl）。然而，这两种代谢产物在莲中的生物合成机制仍 largely 未知。本研究采用生理学和RNA测序（RNA-Seq）方法来表征莲胚芽中双BIAs和Chl生物合成的发育及分子机制。生理学分析表明，授粉后9至15天（DAP）莲胚芽呈指数生长，这与双BIAs生物合成的开始及其随后的快速积累相吻合。莲胚芽的转录组分析共鉴定出8725个差异表达基因（DEGs），占莲基因组所有转录本的约27.7%。鉴定出16个可能与双BIAs生物合成相关的结构DEGs。其中，12个编码 -甲基转移酶（OMTs）可能参与莲中双BIAs的甲基化和多样性。此外，还鉴定出了BIAs生物合成途径功能不同的旁系同源和冗余同源基因成员，以及与双BIAs和Chl生物合成基因共表达的转录因子。鉴定出22个编码Chl生物合成途径16种保守酶的基因，其中大多数在Chl生物合成过程中显著上调。莲胚芽发育过程中光合作用和Chl生物合成途径同时被激活。此外，我们的结果表明光驱动的原叶绿素酸酯还原对莲胚芽中的Chl生物合成至关重要。这些结果将有助于增进我们对植物中生物碱和Chl生物合成的理解。
