Abstract
Ginkgo (Ginkgo biloba L.) is a high-value medicinal tree species characterized by its flavonoids beneficial effects that are abundant in leaves. We performed a temporospatial comprehensive transcriptome and metabolome dynamics analyses of clonally propagated Ginkgo plants at four developmental stages (time: May to August) across three different environments (space) to unravel leaves flavonoids biosynthesis variation. Principal component analysis revealed clear gene expression separation across samples from different environments and leaf-developmental stages. We found that flavonoid-related metabolism was more active in the early stage of leaf development, and the content of total flavonoid glycosides and the expression of some genes in flavonoid biosynthesis pathway peaked in May. We also constructed a co-expression regulation network and identified eight GbMYBs and combining with other TF genes (3 GbERFs, 1 GbbHLH, and 1 GbTrihelix) positively regulated the expression of multiple structural genes in the flavonoid biosynthesis pathway. We found that part of these GbTFs (Gb_11316, Gb_32143, and Gb_00128) expressions was negatively correlated with mean minimum temperature and mean relative humidity, while positively correlated with sunshine duration. This study increased our understanding of the molecular mechanisms of flavonoids biosynthesis in Ginkgo leaves and provided insight into the proper production and management of Ginkgo commercial plantations.
Highlights
Ginkgo (Ginkgo biloba L.) leaves contain a variety of medicinal compounds, which have been used in healthcare and food industries
The Kyoto Encyclopedia of Genes and Genomics (KEGG) pathway enrichment analysis (Figure 3C) indicated that the expression of genes from Profile 0 presented a down-regulated trend with leaf development, and these genes were significantly enriched in both phenylpropanoid and flavonoid biosynthesis pathways. These results indicated that a set of genes related to flavonoid biosyntheses, such as structural genes and transcription factor (TF) genes, performed the stage-specific function under external environmental stimuli
These findings were confirmed by the result of high-performance liquid chromatography (HPLC) analysis; where we found that the content of total flavonoid glycosides (TFG) peaked in the early stage (Figure 1A)
Summary
Ginkgo (Ginkgo biloba L.) leaves contain a variety of medicinal compounds, which have been used in healthcare and food industries. Flavonoids are the major bioactive ingredients in Ginkgo leaves, including flavonols, flavones, and anthocyanins (Meng et al, 2019) These molecules have been reported to have beneficial effects in preventing metabolic syndrome at different levels such as early stage Alzheimer’s and cardiovascular diseases (Tian et al, 2017; Gruenwald et al, 2020). Transcriptome libraries have been constructed for various Ginkgo tissues (Ye et al, 2019) and leaves with different flavonoid contents (Wu et al, 2018), for improving the understanding of flavonoid biosynthesis Another strategy for improving Ginkgo leaves metabolites yield is through genetic engineering; detailed information on gene expression profiling and transcriptional dynamics that regulate flavonoids accumulation is scarce
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