Light-activated lily genes unlock petal color secrets
image: This figure illustrates the influence of LvBBX24 and LvbZIP44 on anthocyanin synthesis. Acting as individual transcription factors, LvBBX24 and LvbZIP44 can modulate anthocyanin accumulation by binding to the LvMYB5 promoter. LvBBX24, a member of the typical BBX protein family, is upregulated in response to light. Exposure of lily petals to daylight increases LvBBX24 expression, thereby enhancing LvMYB5 transcription and promoting anthocyanin accumulation. Moreover, elevated LvBBX24 levels enable complex formation with LvbZIP44, binding to the primary G-box site to change the configuration of the promoter. Subsequently, LvBBX24 undergoes rapid degradation, while LvbZIP44 assumes a pivotal role in enhancing anthocyanin accumulation by binding to the LvMYB5 promoter. In summary, our study unveils novel functionalities of LvBBX24 and LvbZIP44 in anthocyanin synthesis, enriching our understanding of the regulatory network governing anthocyanin biosynthesis.
Credit: Horticulture Research
The dazzling colors of lily petals are powered by anthocyanins, but how these pigments respond to light has long remained a mystery. In this new study, scientists discovered that two transcription factors—LvBBX24 and LvbZIP44—coordinate to drive anthocyanin production when exposed to light. LvBBX24 acts as a light-sensitive trigger, activating the expression of LvMYB5, a gene central to anthocyanin biosynthesis. LvbZIP44, although unaffected by light, physically interacts with LvBBX24 to enhance its regulatory power. Together, they orchestrate a dual-switch mechanism that amplifies pigment accumulation. This finding uncovers a key missing link in how lilies translate light signals into vivid petal coloration.
Lilies (Lilium spp.) are among the world’s most cherished ornamental flowers, valued for their beauty and commercial appeal. Their distinctive pink and purple tones stem from anthocyanins—plant pigments that also help defend against environmental stress. While the chemical pathway producing anthocyanins is conserved across plants, the regulatory systems governing their light-induced activation in monocots like lilies remain largely unexplored. Transcription factors such as MYB and BBX are known to play roles in pigment control, but the specific interactions that modulate gene expression in response to light remain obscure. Because of these unanswered questions, deeper investigation into transcriptional regulation under light exposure is urgently needed.
A research team from Shenyang Agricultural University has taken a major step in decoding how light shapes the color of lily petals. Published (DOI: 10.1093/hr/uhae211) on July 30, 2024, in Horticulture Research, their study identifies two transcription factors—LvBBX24 and LvbZIP44—that form a regulatory duo to activate LvMYB5, a gene essential for anthocyanin biosynthesis. Their work reveals a new molecular mechanism by which light exposure is translated into vibrant petal coloration, offering valuable insights for ornamental breeding and plant molecular biology.
The scientists began by exposing lily petals to light and monitoring pigment changes. They observed that light not only intensified petal color but also boosted expression of anthocyanin biosynthetic genes such as LvCHS and LvANS. Through transcriptome analysis, they identified LvBBX24 as a light-responsive gene whose expression increases with illumination. Silencing LvBBX24 led to a sharp decline in pigment levels and downregulation of LvMYB5, a known anthocyanin activator, while overexpressing LvBBX24 produced deeper pigmentation. Interestingly, LvBBX24 was also found to degrade rapidly in darkness, emphasizing its light-dependent role.
Further analysis revealed that LvBBX24 binds directly to the promoter of LvMYB5. A yeast two-hybrid screen identified LvbZIP44 as its interaction partner. Though not light-responsive itself, LvbZIP44 also binds to the LvMYB5 promoter and independently stimulates pigment production. The duo demonstrated a synergistic effect when co-expressed—amplifying promoter activity and anthocyanin accumulation more strongly than either factor alone. Silencing both genes resulted in a dramatic drop in pigment levels, confirming their cooperative function. Electrophoretic mobility shift assays showed that each factor binds to distinct G-box elements, suggesting they reshape the promoter's architecture to activate LvMYB5 more effectively.
“This research uncovers a finely tuned mechanism that connects light perception to pigment production in lilies,” said Dr. Lijing Chen, the study’s corresponding author. “LvBBX24 acts like a light-sensitive gatekeeper, while LvbZIP44 provides stable support regardless of lighting conditions. Their interaction ensures a robust response, allowing the plant to adjust its petal coloration to environmental cues. This dual regulatory model could have broad implications not just for lilies, but also for understanding how flowering plants use light to shape their appearance.”
The discovery of this two-factor regulatory system opens new avenues for horticultural innovation. By targeting LvBBX24 and LvbZIP44, breeders could develop lily varieties with brighter, more consistent petal colors that respond dynamically to light. This mechanism may also be leveraged in other ornamental or crop species to enhance visual traits or stress resilience. Moreover, understanding how plants use interacting transcription factors to fine-tune gene expression sheds light on broader regulatory networks in plant development. Future research could explore how this mechanism integrates with hormonal or temperature signals, providing a blueprint for precise manipulation of plant traits through genetic engineering.
###
References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae211
Funding information
This work was financially supported by Funds for the China Agriculture Research System (CARS-23) and National Key R & D Program of China (Grant No. 2019YFD1001002).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.