Abstract
BackgroundMatricaria recutita (German chamomile) and Chamaemelum nobile (Roman chamomile) belong to the botanical family Asteraceae. These two herbs are not only morphologically distinguishable, but their secondary metabolites – especially the essential oils present in flowers are also different, especially the terpenoids. The aim of this project was to preliminarily identify regulatory mechanisms in the terpenoid biosynthetic pathways that differ between German and Roman chamomile by performing comparative transcriptomic and metabolomic analyses.ResultsWe determined the content of essential oils in disk florets and ray florets in these two chamomile species, and found that the terpenoid content in flowers of German chamomile is greater than that of Roman chamomile. In addition, a comparative RNA-seq analysis of German and Roman chamomile showed that 54% of genes shared > 75% sequence identity between the two species. In particular, more highly expressed DEGs (differentially expressed genes) and TF (transcription factor) genes, different regulation of CYPs (cytochrome P450 enzymes), and rapid evolution of downstream genes in the terpenoid biosynthetic pathway of German chamomile could be the main reasons to explain the differences in the types and levels of terpenoid compounds in these two species. In addition, a phylogenetic tree constructed from single copy genes showed that German chamomile and Roman chamomile are closely related to Chrysanthemum nankingense.ConclusionThis work provides the first insights into terpenoid biosynthesis in two species of chamomile. The candidate unigenes related to terpenoid biosynthesis will be important in molecular breeding approaches to modulate the essential oil composition of Matricaria recutita and Chamaemelum nobile.
Highlights
Matricaria recutita (German chamomile) and Chamaemelum nobile (Roman chamomile) belong to the botanical family Asteraceae
We compared genes between German chamomile and Roman chamomile, as well as from other Compositae family plants based on Pfam database, and the results showed that unigenes encoding Transcription factors (TFs) such as WD-repeat and zinc-finger proteins were more prevalent in German chamomile and Roman chamomile compared to other plants in the Compositae
We found there are more monoterpenoids and sesquiterpenoids in flowers of German chamomile compared to Roman chamomile, and these compounds were more prevalent in disk florets than in ray florets
Summary
Matricaria recutita (German chamomile) and Chamaemelum nobile (Roman chamomile) belong to the botanical family Asteraceae. These two herbs are morphologically distinguishable, but their secondary metabolites – especially the essential oils present in flowers are different, especially the terpenoids. The flowers of German chamomile contain 0.2 to 1.9% essential oils [2] that consist mainly of terpenoids. The essential oil, which is present in the dried flowers of Roman chamomile (Chamaemelum nobile) at 0.3–1.5%, consists mainly of esters and a small amount sesquiterpenes such as angelic acid, angelic acid butyl ester, and chamazulene [5, 6]. The oil is used to treat mild skin irritation and inflammation [3] [7, 8]
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