Metabolomic and transcriptomic analyses of mutant yellow leaves provide insights into pigment synthesis and metabolism in Ginkgo biloba

Yaqiong Wu,Tongli Wang,Guibin Wang,Fuliang Cao,Jing Guo

doi:10.1186/s12864-020-07259-6

Abstract

BackgroundGinkgo (Ginkgo biloba L.) is an excellent landscape species. Its yellow-green leaf mutants are ideal materials for research on pigment synthesis, but the regulatory mechanism of leaf coloration in these ginkgo mutants remains unclear.ResultsWe compared the metabolomes and transcriptomes of green and mutant yellow leaves of ginkgo over the same period in this study. The results showed that the chlorophyll content of normal green leaves was significantly higher than that of mutant yellow leaves of ginkgo. We obtained 931.52M clean reads from different color leaves of ginkgo. A total of 283 substances in the metabolic profiles were finally detected, including 50 significantly differentially expressed metabolites (DEMs). We identified these DEMs and 1361 differentially expressed genes (DEGs), with 37, 4, 3 and 13 DEGs involved in the photosynthesis, chlorophyll, carotenoid, and flavonoid biosynthesis pathways, respectively. Moreover, integrative analysis of the metabolomes and transcriptomes revealed that the flavonoid pathway contained the upregulated DEM (−)-epicatechin. Fourteen DEGs from the photosynthesis pathway were positively or negatively correlated with the DEMs.ConclusionsOur findings suggest a complex metabolic network in mutant yellow leaves. This study will provide a basis for studies of leaf color variation and regulation.

Highlights

Ginkgo (Ginkgo biloba L.) is an excellent landscape species
The overall distribution among samples and the stability of the entire analytical process were examined by unsupervised principal component analysis (PCA), followed by supervised orthogonal partial least squares discriminant analysis (OPLS-DA)
Among the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, we identified three differentially expressed genes (DEGs) that were significantly upregulated in association with carotenoid biosynthesis in yellow leaves, including DWARF27, NCED (9-cis-epoxycarotenoid dioxygenase; Gb_33714), and CYP707A ((+)-abscisic acid 8′-hydroxylase; Gb_09843) (Fig. 4c)

Summary

Introduction

Ginkgo (Ginkgo biloba L.) is an excellent landscape species. Its yellow-green leaf mutants are ideal materials for research on pigment synthesis, but the regulatory mechanism of leaf coloration in these ginkgo mutants remains unclear. Ginkgo (Ginkgo biloba L.) is a one of the oldest dioecious gymnosperms [1], with a history dating back to approximately 200 million years ago [2, 3]. It is an important multipurpose tree species with medicinal and ornamental value [4]. The medicinal value of ginkgo is mainly due to the secondary metabolites of this plant, such as the flavonoids and terpene lactones in its leaves [5]. Ginkgo is an excellent landscape species, especially for its golden leaves in autumn, and has been widely planted all over the world [7]. A pigmentdeficient mutant of ginkgo, which exhibited a yellowgreen leaf phenotype on the main branch, was discovered and initially identified as a xantha mutant [8]

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