# Metabolomic and Transcriptomic Analyses Reveal the Molecular Mechanism of Flower Color Variations in Rosa chinensis Cultivar ‘Rainbow’s End’

## TL;DR

This study explores how flower color changes in Rosa chinensis cultivar ‘Rainbow’s End’ by analyzing metabolites and gene expression during different blooming stages.

## Contribution

The study identifies key genes and transcription factors involved in anthocyanin and carotenoid pathways responsible for flower color variation in Rosa chinensis.

## Key findings

- Anthocyanidin metabolites peak at R2 and R3 stages, correlating with red coloration.
- Carotenoid levels are highest at R1 and decline with blooming, linked to yellow coloration.
- Specific MYB transcription factors regulate genes in anthocyanin and carotenoid biosynthesis pathways.

## Abstract

Background: Rosa chinensis, commonly known as the Chinese rose, is one of the most economically significant ornamental plants worldwide. The Rosa chinensis cultivar ‘Rainbow’s End’ notably transitions in color from yellow to red throughout its blooming phase; however, the chemical and molecular foundations underlying this floral color transformation remain inadequately understood. Methods: This study used the petals of the Rosa ‘Rainbow’s End’ cultivar at four developmental stages (R1, R2, R3, and R4) for targeted metabolomic and transcriptomic analyses. Results: Targeted metabolomic analyses revealed that the majority of anthocyanidin metabolites were highest at stages R2 and R3 and lowest at R1 and R4. In contrast, most carotenoid metabolites reached their highest levels at R1 and declined continuously from R2 to R4. These results were consistent with the color phenotype of Rosa ‘Rainbow’s End’ petals and suggested that both anthocyanins and carotenoids play critical roles in flower color variation. Specifically, an upregulation of CHS, ANS, and UGT genes in the anthocyanin biosynthesis pathway was observed in R2 and R3, coinciding with the expression of two MYB transcription factors (MYB14 and MYB54). Conversely, consistent downregulation of PSY, PDS, Z-ISO, ZDS, CHYB, and NCED genes in the carotenoid biosynthesis pathway was detected in R2 to R4 and was associated with four MYB transcription factors (MYB20, MYB43, MYB44, and MYB86). Conclusions: Rosa ‘Rainbow’s End’ is an excellent model for studying variations in flower color. The expression patterns of the identified structural genes involved in anthocyanin and carotenoid biosynthesis pathways, along with the related MYB transcription factors, were aligned with the levels of metabolite changes in the petals of four flowering stages. These genes and transcription factors are likely responsible for the color shifts in Rosa ‘Rainbow’s End’. This study clarifies the mechanisms underlying color changes in Rosa ‘Rainbow’s End’ and provides a theoretical basis for future flower breeding efforts.