Transcriptomic analysis reveals biosynthesis genes and transcription factors related to leaf anthocyanin biosynthesis in Aglaonema commutatum

Abstract

Background: Aglaonema commutatum 'Red Valentine', as a foliage ornamental plant, is widely used for interior and exterior decoration because of its easy cultivation and management. However, reduced proportion of red foliage during large-scale production of A. commutatum seedlings is a frequent occurrence, which has considerable implications on the plant's ornamental and market value. However, the molecular mechanisms underlying this phenomenon remain unclear.

Results: To explore the molecular basis of the variation in leaf color of A. commutatum Red Valentine, we performed transcriptome sequencing with the Illumina platform using two different varieties of A. commutatum, namely Red Valentine and a green mutant, at three different stages of leaf development. We annotated 63,621 unigenes and 14,186 differentially expressed genes by pairwise comparison. Furthermore, we identified 26 anthocyanin biosynthesis structural genes. The transcript per million (TPM) values were significantly higher for Red Valentine than for the green mutant in all three developmental stages, consistent with the high anthocyanin content of Red Valentine leaves. We detected positive transcription factors that may be involved in the regulation of anthocyanin biosynthesis using BLAST and through correlation analysis. Downregulation of these transcription factors may downregulate the expression of anthocyanin genes. We obtained full-length cDNA of the anthocyanin biosynthesis and regulatory genes and constructed phylogenetic trees to ensure accuracy of the analysis.

Conclusions: Our study provides insights into the molecular mechanisms underlying leaf variation in A. commutatum Red Valentine and may be used to facilitate the breeding of ornamental cultivars with high anthocyanin levels.

Keywords: Aglaonema commutatum ‘red valentine’; Anthocyanin biosynthesis; R2R3-MYB; Transcriptional regulation; Transcriptomics.

Fig. 1

Morphological characteristics of Aglaonema commutatum leaves. A Pigmentation and phenotypes of A. commutatum Red Valentine and the green mutant. B Leaf phenotypes: stage 1, white curly leaves with small amount of pigment (7 d); stage 2, uncurled leaves exhibiting light pink coloration (28 d); stage 3: mature leaves exhibiting dark red coloration with oily surface (35 d). R1, R2, and R3: stages 1, 2, and 3 of A. commutatum Red Valentine, respectively; G1, G2, and G3: stages 1, 2 and 3 of the green mutant, respectively. The scale bars are 1 cm. C Anatomical observation of pigments in the lamina of A. commutatum Red Valentine and a green mutant. The scale bars are 100 μm

Fig. 2

Pigment accumulation in the leaves of Aglaonema commutatum Red Valentine and a green mutant at three developmental stages. A Total anthocyanin content. B Total chlorophyll content. C Anthocyanin/chlorophyll ratio. D Anthocyanin monomer content

Fig. 3

Functional annotation and classification. A Gene ontology (GO) classification of unigenes. B Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway classification. C Numbers of functional annotation of all unigenes in six databases. D Species distribution of unigenes matching the main species obtained using BLASTx in the NR database

Fig. 4

Identification of differentially expressed genes (DEGs) in Aglaonema commutatum Red Valentine. A Venn diagrams of the DEGs. B List of DEGs between pairs of treatments. C KEGG pathway enrichment of DEGs in G1 vs. G2, G2 vs. G3, R1 vs. R2, and R2 vs. R3

Fig. 5

Heatmap of differentially expressed genes (DEGs) related to anthocyanin biosynthesis. The pathway can be divided into two sections: the phenylpropanoid and flavonoid pathways and early (EBGs) and late biosynthesis genes (LBGs) are involved in the flavonoid pathway

Fig. 6

Top 20 transcription factors in the leaves of Aglaonema commutatum Red Valentine and a green mutant

Fig. 7

Comparative expression of candidate genes in the Red Valentine variety. Real-time qPCR of PAL1 (TRINITY_DN98590_c0_g3); PAL3 (TRINITY_DN89524_c3_g6); C4H (TRINITY_DN95047_c0_g1); 4CL (TRINITY_DN95116_c0_g1); CHS1 (TRINITY_DN78614_c3_g1); UFGT2 (TRINITY_DN90166_c0_g1); F3’H1 (TRINIY_DN103984_c0_g1); DFR1 (TRINITY_DN75107_c2_g1); DFR3 (TRINITY_DN99635_c0_g4); AcbHLH; AcMYB1; AcMYB2 in A. commutatum Red Valentine leaves. The columns represent means ± standard deviations from three independent biological replicates