Genome-Wide Identification and Expression Analysis of R2R3-MYB Family Genes Associated with Petal Pigment Synthesis in Liriodendron

Lichun Yang,Ziyuan Hao,Yaxian Zong,Huanhuan Liu,Yufang Shen,Huogen Li,Hui Xia

doi:10.3390/ijms222011291

Lichun Yang, Ziyuan Hao + Show 5 more

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https://doi.org/10.3390/ijms222011291

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Abstract

The MYB transcription factor family is one of the largest families in plants, and its members have various biological functions. R2R3-MYB genes are involved in the synthesis of pigments that yield petal colors. Liriodendron plants are widely cultivated as ornamental trees owing to their peculiar leaves, tulip-like flowers, and colorful petals. However, the mechanism underlying petal coloring in this species is unknown, and minimal information about MYB genes in Liriodendron is available. Herein, this study aimed to discern gene(s) involved in petal coloration in Liriodendron via genome-wide identification, HPLC, and RT-qPCR assays. In total, 204 LcMYB superfamily genes were identified in the Liriodendron chinense genome, and 85 R2R3-MYB genes were mapped onto 19 chromosomes. Chromosome 4 contained the most (10) R2R3-MYB genes, and chromosomes 14 and 16 contained the fewest (only one). MEME analysis showed that R2R3-MYB proteins in L. chinense were highly conserved and that their exon-intron structures varied. The HPLC results showed that three major carotenoids were uniformly distributed in the petals of L. chinense, while lycopene and β-carotene were concentrated in the orange band region in the petals of Liriodendron tulipifera. Furthermore, the expression profiles via RT-qPCR assays revealed that four R2R3-MYB genes were expressed at the highest levels at the S3P/S4P stage in L. tulipifera. This result combined with the HPLC results showed that these four R2R3-MYB genes might participate in carotenoid synthesis in the petals of L. tulipifera. This work laid a cornerstone for further functional characterization of R2R3-MYB genes in Liriodendron plants.

Highlights

To test whether R2R3-MYB genes are involved in the accumulation of carotenoids or pigments synthesis during L. tulipifera floral development, we identified the R2R3-MYB gene family and revealed the precise spatiotemporal characteristics of orange band formation during L. tulipifera floral development based on the L. chinense genome and high-performance liquid chromatography (HPLC) results
85 R2R3-MYB genes were located across all 19 chromosomes; 14 genes were located on Contigs
We identified members of clade C4 in L. chinense for which there are no representatives in A. thaliana, suggesting that these proteins might have specific functions that were either lost in Arabidopsis or differentiated at the time of the last common ancestor

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. MYB transcription factors (TFs) compose one of the largest superfamilies of TFs and exhibit various biological functions in plants. MYB proteins contain a conserved DNAbinding domain composed of one to four conserved repeats comprising approximately. MYB superfamily genes are grouped into MYB-related (1R-MYB), R2R3-MYB (2R-MYB), R1R2R3-MYB (3R-MYB), and 4R-MYB genes according to the number of imperfect MYB tandem repeats [1,2]. The R1R2R3-MYB family is the largest of the MYB superfamily in animals, while in plants, the R2R3-MYB family is the largest [3]. There are 126 R2R3-MYB genes and 5 R1R2R3-MYB genes in Arabidopsis thaliana [4,5]

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