Transcriptome Analysis Reveals Molecular Signatures of Luteoloside Accumulation in Senescing Leaves of Lonicera macranthoides.

Zexiong Chen,Zexiong Chen,Ning Tang,Ning Tang,Zhengguo Li,Zhengguo Li,Guohua Liu

doi:10.3390/ijms19041012

Abstract

Lonicera macranthoides is an important medicinal plant widely used in traditional Chinese medicine. Luteoloside is a critical bioactive compound in L. macranthoides. To date, the molecular mechanisms underlying luteoloside biosynthesis are still largely unknown. In this work, high performance liquid chromatography (HPLC) was employed to determine the luteoloside contents in leaves, stems, and flowers at different developmental stages. Results showed that senescing leaves can accumulate large amounts of luteoloside, extremely higher than that in young and semi-lignified leaves and other tissues. RNA-Seq analysis identified that twenty-four differentially expressed unigenes (DEGs) associated with luteoloside biosynthesis were significantly up-regulated in senescing leaves, which are positively correlated with luteoloside accumulation. These DEGs include phenylalanine ammonia lyase 2, cinnamate 4-hydroxylase 2, thirteen 4-coumarate-CoA ligases, chalcone synthase 2, six flavonoid 3′-monooxygenase (F3′H) and two flavone 7-O-β-glucosyltransferase (UFGT) genes. Further analysis demonstrated that two F3′Hs (CL11828.Contig1 and CL11828.Contig2) and two UFGTs (Unigene2918 and Unigene97915) might play vital roles in luteoloside generation. Furthermore, several transcription factors (TFs) related to flavonoid biosynthesis including MYB, bHLH and WD40, were differentially expressed during leaf senescence. Among these TFs, MYB12, MYB75, bHLH113 and TTG1 were considered to be key factors involved in the regulation of luteoloside biosynthesis. These findings provide insights for elucidating the molecular signatures of luteoloside accumulation in L. macranthoides.

Highlights

Lonicera macranthoides, a member of the Caprifoliaceae family, is a medicinal plant primarily distributed in Southern China
Luteoloside contents fluctuated throughout the flower development and the highest luteoloside level in flowers was found in white flower, followed by green flower buds in length of 10 mm (Figure 1E,F)
In terms of the roles of testa glabrous1 (TTG1) in regulating flavonoid biosynthesis, we considered that Unigene108470 might be the candidate factor in controlling luteoloside biosynthesis

Summary

Introduction

A member of the Caprifoliaceae family, is a medicinal plant primarily distributed in Southern China It has been widely used as a critical raw material in traditional Chinese medicine for thousands of years, because it can effectively treat H1N1, respiratory syndrome, and hand-foot-and-mouth disease (China Pharmacopeia Commission, 2010). A subset of secondary metabolites, including flavonoids, phenolic acid, volatile oil and saponins, is present in whole plants of L. macranthoides [3]. These components possess a wide range of pharmacological activities, such as antioxidant, anti-inflammatory, antibacterial, antiviral, antipyretic, liver protective and anticancer effects [4,5,6]. The knowledge of quantitative profiling for luteoloside is of major importance for characterizing molecular basis of luteoloside biosynthesis and has significant implications for health benefits of L. macranthoides

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Discussion

Conclusion