Abstract
Ornamental kale is a popular decorative plant. We identified a peculiar bicolor leaf double haploid line, with green margins and red centers. The development of bicolor leaves can be divided into three stages: S1, S2, and S3. To probe the reason for bicolor formation, we analyzed the anthocyanin and chlorophyll contents, detected the changes in indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellin 3 (GA3), sugar, and starch contents, and identified the differentially expressed genes (DEGs) using RNA-seq. Results showed that the bicolor leaf phenotype is gradually formed with anthocyanin degrading and chlorophyll accumulation. Anthocyanin content is lower in the green margin (S3_S) than in the red center (S3_C) part at S3. IAA content was positively correlated with anthocyanin content during the bicolor leaf development. During anthocyanin degrading from S1 to S2, cinnamate-4-hydroxylase (C4H) and transport inhibitor response 1 (TIR1) were downregulated, while lateral organ boundaries domain 39 (LBD39) was upregulated. Two peroxidases, two β-glucosidases (BGLU), LBD39, LBD37, detoxifying efflux carrier 35 (DTX35), three no apical meristem (NAC) transcription factors (TFs), and 15 WRKY DNA-binding protein (WRKY) TFs were downregulated in S3_S vs. S3_C. The bicolor phenotype was mainly linked to anthocyanin degrading and chlorophyll accumulation, and that anthocyanin degrading resulted from reduced anthocyanin biosynthesis and increased anthocyanin degradation.
Highlights
Ornamental kale (Brassica oleracea L. var. acephala) is popular because of its bright color and various leaf shapes
The gene expression patterns of the differentially expressed genes (DEGs) involved in pigment biosynthesis were validated by Quantitative Real-Time PCR (qRT-PCR) (Figure 7, Table S8), which indicated that the transcriptome analysis was reliable
The expression patterns of the anthocyanin biosynthesis genes were consistent with the changes in anthocyanin content at stage 2 (S2) compared to stage 1 (S1), S3_S compared to S3_C, and S3_S compared to S2 (Figure 10)
Summary
Ornamental kale (Brassica oleracea L. var. acephala) is popular because of its bright color and various leaf shapes. The genes involved in the regulation of anthocyanin biosynthesis have been identified. A set of DEGs were identified as involved in anthocyanin degrading and bicolor formation. This information might be applied for breeding plants with desirable color traits and it lays the foundation for further genetic studies on anthocyanin degradation in ornamental kale and other plants. DDiiffffeerreenntt lleetttteerrss aammoonngg ssttaaggeess iinnddiiccaattee ssiiggnniifificcaanntt ddiiffffeerreenncceess aatt pp ≤≤ 00..0011 bbaasseedd oonn tthhee aannaallyyssiiss ooff vvaarriiaannccee((AANNOOVVAA))((TTuukkeeyytetesst)t.). IAA, ABA, GA3, Sugar, and Starch Contents in Leaves Previous studies showed that plant hormone and sugar contents are related with anthocyanin accumPurelavtiioouns. The gene expression patterns of the DEGs involved in pigment biosynthesis were validated by qRT-PCR (Figure 7, Table S8), which indicated that the transcriptome analysis was reliable
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