Transcriptome and proteome associated analysis of flavonoid metabolism in haploid Ginkgo biloba

Having different number if genome copies affect transcription and metabolite production of plants. This may be due to different gene transcription and protein expression, but the reasons for this remains poorly known. Here we measured flavonoid content in leaves of three haploid and diploid grafted plants of Ginkgo biloba, a model gymnosperm important economically for its flavonoid content. We reported the first combined transcriptomic and proteomic analysis of the difference in flavonoid content in three haploid ginkgos to investigate the effect of haploidy. Haploids had always smaller leaves and flavonoid content than the diploids. The selected haploid had also generally lower gene dosage than the selected diploid, with 1149 up-regulated (46.8 %) and 1309 down-regulated (53.2 %) among 2452 differentially expressed genes (DEGs). Of 686 differentially expressed proteins (DEPs) detected, 289 proteins (42.1 %) were upregulated, and 397 proteins (57.9 %) were downregulated in haploids. A particular attention deserves the downregulation of PAL, PAM, FLS, OMT1 hub genes involved in flavonoid biosynthesis regulation. Our study confirms the trend of haploids to have lower metabolic contents and points that lower flavonoid content in ginkgo monoploids could be due to reduced dosage of the corresponding regulatory genes and downregulation of genes involved in flavonoid synthesis.