Regulation of Fig (Ficus carica L.) Fruit Color: Metabolomic and Transcriptomic Analyses of the Flavonoid Biosynthetic Pathway

Abstract

Combined metabolomic and transcriptomic analyses were carried out with fig cultivar Green Peel and its color mutant “Purple Peel.” Five and twenty-two metabolites were identified as having significantly different contents between fruit peels of the two cultivars at young and mature stages, respectively. Cyanidin O-malonylhexoside demonstrated a 3,992-fold increase in the mature purple peel, the first identification of a major cyanidin in fig fruit; cyanidin 3-O-glucoside, cyanidin O-malonylhexoside O-hexoside and cyanidin-3,5-O-diglucoside were upregulated 100-fold, revealing the anthocyanins underlying the purple mutation. Beyond the visible differences, there was very significant accumulation of the colorless flavonoids procyanidin B1, luteolin-3′,7-di-O-glucoside, epicatechin and quercetin-3-O-rhamnoside in the mature “Purple Peel” compared to “Green Peel.” At the young stage, only cyanidin O-malonylhexoside, cyanidin O-malonylhexoside O-hexoside and esculetin were upregulated a few fold in the mutant. Transcriptome analysis revealed a downregulated expression trend of genes encoding phenylpropanoid and flavonoid biosynthetic pathway enzyme in the young “Purple Peel” compared to the young “Green Peel,” whereas significant and simultaneous upregulation was revealed in almost all of the flavonoid and anthocyanin pathway components and relevant transcription factors in the mature-stage mutant. The role of R2R3-MYB transcription factors in the color morph mutation and its possible relation to the activity of retrotransposons are discussed. Moreover, large-scale upregulation of small heat-shock protein genes was found in the mature mutant. This is the first work to reveal comprehensive metabolome and transcriptome network changes underlying a fig mutation in a single horticultural attribute, and its profound effects on fruit nutrition and quality.

Comparative Metabolomic Analysis Reveals Distinct Flavonoid Biosynthesis Regulation for Leaf Color Development of Cymbidium sinense ‘Red Sun’

“…As [18]. In this study, 119 kinds of differential flavonoid-related metabolites were found (including 10 kinds of anthocyanins).…”

“…A study on green and purple asparagus suggested that the difference in color was mainly caused by the contents of peonidin and cyanidin and their glycoside derivatives [17]. Metabolomic analysis the color difference of fig peel showed that the content of anthocyanin derivatives in purple peel was significantly higher than that in green fruit [18]. These results indicate that metabolomics is an important and effective method to analyze the formation mechanism of plant color.…”

Metabolomics Analysis of the Peels of Different Colored Citrus Fruits (Citrus reticulata cv. ‘Shatangju’) During the Maturation Period Based on UHPLC-QQQ-MS

“…Plant metabolomics can yield a large amount of qualitative and quantitative data on metabolites according to the organism-specific metabolic pathways, metabolic networks, and functions that the metabolites participate in; thus, biologically meaningful data can be retrieved [13]. Plant metabolomic studies have been of value for the identification of metabolites, regional differences, natural variations, and intraspecific and interspecific differences in citrus fruits [14,15], figs [16], and tomatoes [17]. Therefore, plant metabolomics can be a good tool to improve upon plant research.…”

Analysis of Antioxidant Activity and Flavonoids Metabolites in Peel and Flesh of Red-Fleshed Apple Varieties

“…Previously, the techniques for detecting metabolites were mainly depended on single technique such as column chromatography, gas chromatography (GC) and liquid chromatography (LC), then the integrated approaches like gas chromatograph-mass spectrometer (GC-MS) and liquid chromatograph-mass spectrometer (LC-MS) became promising tools for the study of plant metabolites diversity [20,21]. Recently, more advanced technique LC-Electrospray Ionization−tandem mass spectrometry (LC-ESI-MS/MS) has emerged and been widely used in flavonoids study [22][23][24]. Nowadays, the relationship between differential metabolites profiles and biochemical properties could be analyzed based on the advanced metabolomics techniques [24].…”

“…The cutting edges of metabolomics approaches allow more accurate and precise identification of metabolites in biosynthetic pathway. Significant different metabolites in flavonoid biosynthetic pathway were reported in purple fig mutation compared to the green control [23]. The interaction of the primary and secondary metabolites profiles combined with proteomics elucidated the accumulation of phenolic substances and other major compounds related to flavonoids accumulation during seed development in cacao [25].Over the past decade, studies related to red-fleshed apple were mainly focused on the structural and regulatory genes which play important roles in anthocyanins biosynthesis [26][27][28][29].…”