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. 2021 Mar 21;12(3):449.
doi: 10.3390/genes12030449.

Identification of Chlorophyll Metabolism- and Photosynthesis-Related Genes Regulating Green Flower Color in Chrysanthemum by Integrative Transcriptome and Weighted Correlation Network Analyses

Hansen Fu  1 , Tuo Zeng  1 , Yangyang Zhao  1 , Tingting Luo  1 , Huijie Deng  1 , Chenwei Meng  1 , Jing Luo  1 , Caiyun Wang  1
Affiliations

Identification of Chlorophyll Metabolism- and Photosynthesis-Related Genes Regulating Green Flower Color in Chrysanthemum by Integrative Transcriptome and Weighted Correlation Network Analyses

Hansen Fu et al. Genes (Basel). .

Abstract

Green chrysanthemums are difficult to breed but have high commercial value. The molecular basis for the green petal color in chrysanthemum is not fully understood. This was investigated in the present study by RNA sequencing analysis of white and green ray florets collected at three stages of flower development from the F1 progeny of the cross between Chrysanthemum × morifolium "Lüdingdang" with green-petaled flowers and Chrysanthemum vistitum with white-petaled flowers. The chlorophyll content was higher and chloroplast degradation was slower in green pools than in white pools at each developmental stage. Transcriptome analysis revealed that genes that were differentially expressed between the two pools were enriched in pathways related to chlorophyll metabolism and photosynthesis. We identified the transcription factor genes CmCOLa, CmCOLb, CmERF, and CmbHLH as regulators of the green flower color in chrysanthemum by differential expression analysis and weighted gene co-expression network analysis. These findings can guide future efforts to improve the color palette of chrysanthemum flowers through genetic engineering.

Keywords: chlorophyll metabolism; florist’s chrysanthemum; green ray floret; photosynthesis; segregating population; transcriptome; weighted gene co-expression network analysis (WGCNA).

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Phenotype and chlorophyll accumulation at three stages of flower development. (A) Floret color at each stage of flower development. (B) Chlorophyll content of petals from green and white pools at each stage.
Figure 2
Figure 2
TEM images of plastid ultrastructure. (A–C,G–I) Plastid ultrastructure in the epidermal cells (A–F) and mesophyll cells (G–L) of ray florets of green (A–C,G–I) and white (D–F,J–L) pools. S, starch granule; T, thylakoids; V, lipid vesicles.
Figure 3
Figure 3
Differentially expressed genes (DEGs) between green and white pools at each stage of flower development.
Figure 4
Figure 4
Expression heatmap of DEGs involved in chlorophyll metabolism in different samples.
Figure 5
Figure 5
qRT-PCR analysis of DEGs involved in chlorophyll metabolism in different samples.
Figure 6
Figure 6
Expression heatmap of genes in key pathways that are differentially expressed between green and white pools at three stages of flower development.
Figure 7
Figure 7
Co-expression modules determined by weighted gene co-expression network analysis (WGCNA). (A) Cluster dendrogram of genes in the WGCNA. (B) Heatmap of correlations between module eigengenes and samples. Genes in the black module showed the highest positive correlation with flower color (i.e., chlorophyll content).
Figure 8
Figure 8
Network of genes in the black module. The network was constructed from 51 genes based on edge weight values. The size of the nodes represents the betweenness centrality of the node, with larger nodes having more connections with other nodes.
Figure 9
Figure 9
qRT-PCR analysis of hub genes in green and white pools at different stages of flower development.
Figure 10
Figure 10
qRT-PCR analysis of hub genes in petals of green and white ray florets of chrysanthemum. (A–C) Chlorophyll content (A), color (B), and expression of hub genes in the six commercial cultivars (C).
See this image and copyright information in PMC

References

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