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Transcriptome-Wide Analysis Reveals Key DEGs in Flower Color Regulation of Hosta plantaginea (Lam.) Aschers.

ABSTRACT: BACKGROUND:Hosta plantaginea (Lam.) Aschers (HPA), a species in the family Liliaceae, is an important landscaping plant and herbaceous ornamental flower. However, because the flower has only two colors, white and purple, color matching applications are extremely limited. To date, the mechanism underlying flower color regulation remains unclear. METHODS:In this study, the transcriptomes of three cultivars-H. plantaginea (HP, white flower), H. Cathayana (HC, purple flower), and H. plantaginea 'Summer Fragrance' (HS, purple flower)-at three flowering stages (bud stage, initial stage, and late flowering stage) were sequenced with the Illumina HiSeq 2000 (San Diego, CA, USA). The RNA-Seq results were validated by qRT-PCR of eight differentially expressed genes (DEGs). Then, we further analyzed the relationship between anthocyanidin synthase (ANS), chalcone synthase (CHS), and P450 and the flower color regulation by Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Eukaryotic Orthologous Groups (KOG) network and pathway enrichment analyses. The overexpression of CHS and ANS in transgenic tobacco petals was verified using qRT-PCR, and the petal colors associated with the overexpression lines were confirmed using absorbance values. RESULTS:Over 434,349 transcripts were isolated, and 302,832 unigenes were identified. Additionally, through transcriptome comparisons, 2098, 722, and 606 DEGs between the different stages were found for HP, HC, and HS, respectively. Furthermore, GO and KEGG pathway analyses showed that 84 color-related DEGs were enriched in 22 pathways. In particular, the flavonoid biosynthetic pathway, regulated by CHS, ANS, and the cytochrome P450-type monooxygenase gene, was upregulated in both purple flower varieties in the late flowering stage. In contrast, this gene was hardly expressed in the white flower variety, which was verified in the CHS and ANS overexpression transgenic tobacco petals. CONCLUSIONS:The results suggest that CHS, ANS, and the cytochrome P450s-regulated flavonoid biosynthetic pathway might play key roles in the regulation of flower color in HPA. These insights into the mechanism of flower color regulation could be used to guide artificial breeding of polychrome varieties of ornamental flowers.

SUBMITTER: Zhang J

PROVIDER: S-EPMC7017146 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Transcriptome-Wide Analysis Reveals Key DEGs in Flower Color Regulation of <i>Hosta plantaginea</i> (Lam.) Aschers.

Zhang Jingying J Sui Changhai C Wang Yanli Y Liu Shuying S Liu Huimin H Zhang Zhengren Z Liu Hongzhang H

Genes 20191226 1

<h4>Background</h4><i>Hosta plantaginea</i> (Lam.) Aschers (HPA), a species in the family Liliaceae, is an important landscaping plant and herbaceous ornamental flower. However, because the flower has only two colors, white and purple, color matching applications are extremely limited. To date, the mechanism underlying flower color regulation remains unclear.<h4>Methods</h4>In this study, the transcriptomes of three cultivars-<i>H. plantaginea</i> (HP, white flower), <i>H. Cathayana</i> (HC, pur ...[more]

PMID: 31888085

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Project description:Background'Regal Splendour' (Hosta variety) is famous for its multi-color leaves, which are useful resources for exploring chloroplast development and color changes. The expressions of chlorophyll biosynthesis-related genes (HrHEMA, HrPOR and HrCAO) in Hosta have been demonstrated to be associated with leaf color. Herein, we isolated, sequenced, and analyzed HrHEMA, HrPOR and HrCAO genes. Subcellular localization was also performed to determine the location of the corresponding enzymes. After plasmid construction, virus-induced gene silencing (VIGS) was carried out to reduce the expressions of those genes. In addition, HrHEMA-, HrPOR- and HrCAO-overexpressing tobacco plants were made to verify the genes function. Changes of transgenic tobacco were recorded under 2000 lx, 6000 lx and 10,000 lx light intensity. Additionally, the contents of enzyme 5-aminolevulinic acid (5-ALA), porphobilinogen (PBG), chlorophyll a and b (Chla and Chlb), carotenoid (Cxc), superoxide dismutase (SOD), peroxidase (POD), malondialdehyde (MDA), proline (Pro) and catalase (CAT) under different light intensities were evaluated.ResultsThe silencing of HrHEMA, HrPOR and HrCAO genes can induce leaf yellowing and chloroplast structure changes in Hosta. Specifically, leaves of Hosta with HrCAO silencing were the most affected, while those with HrPOR silencing were the least affected. Moreover, all three genes in tobacco were highly expressed, whereas no expression was detected in wild-type (WT). However, the sensitivities of the three genes to different light intensities were different. The highest expression level of HrHEMA and HrPOR was detected under 10,000 lx of illumination, while HrCAO showed the highest expression level under 6000 lx. Lastly, the 5-ALA, Chla, Cxc, SOD, POD, MDA, Pro and CAT contents in different transgenic tobaccos changed significantly under different light intensities.ConclusionThe overexpression of these three genes in tobacco enhanced photosynthesis by accumulating chlorophyll content, but the influential level varied under different light intensities. Furthermore, HrHEMA-, HrPOR- and HrCAO- overexpressing in tobacco can enhance the antioxidant capacity of plants to cope with stress under higher light intensity. However, under lower light intensity, the antioxidant capacity was declined in HrHEMA-, HrPOR- and HrCAO- overexpressing tobaccos.

Project description:Flower color polymorphisms are widely used as model traits from genetics to ecology, yet determining the biochemical and molecular basis can be challenging. Anthocyanin-based flower color variations can be caused by at least 12 structural and three regulatory genes in the anthocyanin biosynthetic pathway (ABP). We use mRNA-Seq to simultaneously sequence and estimate expression of these candidate genes in nine samples of Silene littorea representing three color morphs (dark pink, light pink and white) across three developmental stages in hopes of identifying the cause of flower color variation. We identified 29 putative paralogs for the 15 candidate genes in the ABP. We assembled complete coding sequences for 16 structural loci and nine of ten regulatory loci. Among these 29 putative paralogs, we identified 622 SNPs, yet only nine synonymous SNPs in Ans had allele frequencies that differentiated pigmented petals (dark pink and light pink) from white petals. These Ans allele frequency differences were further investigated with an expanded sequencing survey of 38 individuals, yet no SNPs consistently differentiated the color morphs. We also found one locus, F3h1, with strong differential expression between pigmented and white samples (>42x). This may be caused by decreased expression of Myb1a in white petal buds. Myb1a in S. littorea is a regulatory locus closely related to Subgroup 7 Mybs known to regulate F3h and other loci in the first half of the ABP in model species. We then compare the mRNA-Seq results with petal biochemistry which revealed cyanidin as the primary anthocyanin and five flavonoid intermediates. Concentrations of three of the flavonoid intermediates were significantly lower in white petals than in pigmented petals (rutin, quercetin and isovitexin). The biochemistry results for rutin, quercetin, luteolin and apigenin are consistent with the transcriptome results suggesting a blockage at F3h, possibly caused by downregulation of Myb1a.

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Transcriptome-Wide Analysis Reveals Key DEGs in Flower Color Regulation of Hosta plantaginea (Lam.) Aschers.

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Transcriptome-Wide Analysis Reveals Key DEGs in Flower Color Regulation of <i>Hosta plantaginea</i> (Lam.) Aschers.

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