Abstract
The Flos Lonicerae Japonicae (FLJ), Lonicera japonica Thunb, belonging to the Caprifoliaceae family, is an economically important plant that is highly utilized in traditional Chinese medicine as well as in Japanese medicine. The flowers of these plants are rich in chlorogenic acid (CGA) and luteoloside. Our previous study revealed that tetraploid L. japonica has higher fresh/dry weight, phenolic acids and flavonoids contents than those of diploid plants. However, why tetraploid L. japonica can yield higher CGA and luteolosides than that in diploid and what is the difference in the molecular regulatory mechanism of these pathways between diploid and tetraploids remained unclear. Therefore, in the present study, we performed comprehensive transcriptome analyses of different flowering stages of diploid and tetraploid L. japonica. The CGA content of tetraploid was found higher than that of diploid at all the growth stages. While the luteoloside content of diploid was higher than that of tetraploid at S4 and S6 growth stages. We obtained a high-quality transcriptome assembly (N50 = 2,055 bp; Average length = 1,331 bp) compared to earlier studies. Differential expression analysis revealed that several important genes involving in plant hormone signal transduction, carbon metabolism, starch/sucrose metabolism and plant-pathogen interaction were upregulated in tetraploid compared with the diploid L. japonica, reflecting the higher adaptability and resistance of tetraploid species. Furthermore, by associating the phenotypic data and gene expression profiles, we were able to characterize the potential molecular regulatory mechanism of important biosynthetic pathways at different flowering stages. Overall, our work provides a foundation for further research on these important secondary metabolite pathways and their implications in traditional Chinese/Japanese medicine.
Highlights
Lonicera japonica Thunb, belonging to the Caprifoliaceae family, is a stolon shrub featured with perennial, evergreen and twining vine, which has been used as an important raw material in Chinese traditional medicine (TCM) as a treatment various diseases such as to clean away the heat-evil or heal the swelling for over thousands of years (Shang et al, 2011; Rai et al, 2017)
To further investigate the molecular regulatory mechanism to correlate with gene expression profile, we measured the chlorogenic acid (CGA) and luteoloside contents in a unit weight of diploid and tetraploid L. japonica throughout the six growth stages
A total of 87,809 unigenes were obtained and RNA-Seq analysis was performed on differentially expressed genes (DEGs) between diploid and tetraploid L. japonica at different growth stages based on these data
Summary
Lonicera japonica Thunb, belonging to the Caprifoliaceae family, is a stolon shrub featured with perennial, evergreen and twining vine, which has been used as an important raw material in Chinese traditional medicine (TCM) as a treatment various diseases such as to clean away the heat-evil or heal the swelling for over thousands of years (Shang et al, 2011; Rai et al, 2017). Modern pharmacological studies suggested that the pharmacological effects of L. japonica are diverse and a wide range of bioactive properties, including anti-bacterial, anti-inflammatory, anti-oxidant, anti-viral, anti-angiogenic, antipyretic, hepatoprotective and anti-tumor effects (Lee et al, 2010; Shang et al, 2011; Kong et al, 2017a). Recent studies indicated these functions are mainly attributed to the complex and diverse chemical composition of L. japonica (Li, Kong & Wu, 2018). Most recently, Wang et al (2019) provided a comprehensive characterization of the expression profiles of transcription factors (TFs) during the developmental stages of L. japonica
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