Position matters: light repatterns m⁶A to tune anthocyanin accumulation in roses

Roses have played a significant part in human history, appearing in some of the earliest written records. Beyond their aesthetic appeal, they have carried symbolic meaning across millennia, including in the religions and cultures of many societies (Goody 1993). Various traits have been bred over time, leading to the tens of thousands of rose varieties cultivated today. One such trait, petal coloration, reflects the accumulation (or absence) of pigments such as anthocyanins and carotenoids. Pigment production is tightly regulated during flower development and in response to environmental cues, including light (Winkel-Shirley 2001). Understanding how pigment biosynthesis is controlled is therefore of major economic importance for rose breeders, both to enable the creation of new varieties and to predict how environmental conditions influence coloration. For example, some cultivars produce inadequate pigmentation when light is limiting.

Anthocyanin biosynthesis, a major contributor to rose petal coloration, proceeds through a multistep pathway involving several enzymes acting in sequence. In hybrid tea rose (Rosa hybrida), the expression of anthocyanin biosynthesis genes in petals is regulated spatially and temporally by transcription factors that form MYB-bHLH-WD40 (MBW) complexes (Lloyd et al. 2017). In some cultivars, such as the light-sensitive R. hybrida cv. Spectra, light helps prevent rapid turnover of the central photomorphogenesis protein RhHY5, which in turn promotes binding of the MBW component RhMYB114a to the promoters of anthocyanin biosynthesis genes, increasing their expression (Yan et al. 2023). By contrast, light-insensitive cultivars such as R. hybrida cv. Samantha do not require light to produce anthocyanins.

Despite a working model of the transcription factor cascade that regulates anthocyanin biosynthetic gene transcription in R. hybrida (Yan et al. 2023), this network only partially explains pigment accumulation. Additional factors are likely involved, including post-transcriptional layers of regulation. Insights from other species provide clues: during strawberry fruit ripening, which involves anthocyanin production, transcript stability of anthocyanin biosynthesis genes has been suggested to be regulated by the RNA modification N⁶-methyladenosine (m⁶A) (Zhou et al. 2021). Such observation raises the question of whether similar RNA modifications also contribute to rose coloration.

Recently in Plant Physiology, Gao et al. (2026) used m⁶A-seq to profile the m⁶A epitranscriptome of R. hybrida cv. Spectra petals under light and dark conditions and found that changes in m⁶A distribution were enriched among transcripts of anthocyanin biosynthesis genes. Among these genes, the anthocyanin synthase gene RhANS showed higher transcript levels and m⁶A abundance within the coding region under light. By contrast, in the dark (where RhANS transcript levels are lower) m⁶A was more abundant within the 3ʹ UTR. Differences in transcript abundance between light and dark were due in part to the increased transcript stability under light, which was accompanied by increased translation efficiency. Together, these findings suggest a link between m⁶A patterning and anthocyanin biosynthesis.

To investigate the possible connection between m⁶A modification and anthocyanin biosynthesis, the authors first transiently overexpressed RhANS in R. hybrida cv. Spectra petal discs under light, which resulted in increased pigmentation. This result confirmed that increased RhANS expression is a key contributor to light-induced pigmentation. Next, the authors identified 2 candidate m⁶A demethylases, RhALKBH10A and RhALKBH10B, both of which were transiently downregulated in petals after initial exposure to light. Using virus-induced gene silencing (VIGS), the authors showed that suppressing the expression of the m⁶A demethylases led to an increase in RhANS transcript levels and m⁶A abundance in the coding region, resulting in pigmentation of petal discs. This increase in pigmentation was abrogated when RhANS was additionally silenced in the VIGS experiments. In summary, the data support a model in which light represses RhALKBH10A/B, allowing accumulation of m⁶A in the coding region. In addition, m⁶A is reduced in the 3ʹ UTR by some yet-unknown mechanism, and together this repatterning of m⁶A leads to increased RhANS stability and translation and boosting anthocyanin accumulation (Fig. 1).

Figure 1.

Proposed model for the role of m⁶A in light-induced anthocyanin biosynthesis in R. hybrida cv. Spectra. In the dark, the m⁶A demethylases RhALKBH10A and RhALKBH10B prevent m⁶A accumulation in the coding region of the anthocyanin synthase RhANS transcript and instead promote m⁶A accumulation in the 3ʹ UTR, reducing transcript stability. After exposure to light, expression of these demethylases is suppressed, triggering a shift in m6A patterning that increases transcript stability and translation efficiency, ultimately promoting petal pigmentation. Adapted from Fig. 6 of Gao et al. (2026).

The findings of Gao et al. further expand our understanding of the regulation of light-induced pigmentation in R. hybrida cv. Spectra by revealing a post-transcriptional regulatory layer that tunes transcript abundance of anthocyanin biosynthesis genes. While this work adds to our understanding of rose pigmentation, it also leaves open questions. For example, although the authors demonstrated the importance of RhANS for pigmentation in the light-sensitive cultivar, they observed low RhANS expression in the light-insensitive R. hybrida cv. Samantha cultivar, suggesting that cultivar-specific regulatory mechanisms may control anthocyanin accumulation and that RhANS transcript abundance may not be a key determinant of pigmentation across all roses.

Finally, this study has broad implications for m⁶A function in plants. Although m⁶A has been shown to play an important role in mediating transcript stability during development and stress responses, the impact of m⁶A patterning is less well understood. Gao et al. found that m⁶A within the coding region of the RhANS transcript was associated with increased transcript stability and translation efficiency, whereas m⁶A within the 3ʹ UTR was associated with decreased transcript stability. It remains to be seen whether these associations are shared by other transcripts, including in other species, and what mechanisms allow m⁶A position to differentially influence these processes.

Recent related articles in Plant Physiology:

• Guan et al. (2025) reviewed the current knowledge of the regulation of rose petal size.

• Gao et al. (2025) found that transcript stability and translation efficiency of volatile biosynthesis genes in tomato were dynamically regulated by m⁶A, contributing to fruit flavor during ripening.

Funding

None declared.

Data availability

None required.