The study, led by Sujuan Xu, Xiaoyu Hu and Ting Li under the supervision of Nianjun Teng and Ze Wu at Nanjing Agricultural University, began with a sweeping computational survey. The researchers searched the genomes of three lily species — Lilium davidii var. unicolor, Lilium sargentiae and Lilium regale — for members of the heat shock transcription factor family, the master switches that plants flip when temperatures rise. What they found was striking: 48 heat shock factor genes in L. davidii var. unicolor, 62 in L. sargentiae and a remarkable 114 in L. regale. Those numbers are large by plant standards and reflect the enormous, duplicated genomes that lilies carry, which have been shaped by transposon insertions and polyploidization events over evolutionary time.

Heat shock transcription factors, or HSFs, sit at the top of the plant heat-response hierarchy. When a plant senses dangerous temperatures, these proteins bind to specific DNA sequences in the promoters of protective genes, switching on the production of heat shock proteins and other molecular chaperones that shield cells from damage. In the model plant Arabidopsis, the family is compact, but in crops and ornamentals it can be far more elaborate. The lily analysis showed that while the core protein domains — the DNA-binding domain and the oligomerization domain that lets HSFs pair up and grab DNA — have been conserved across the family, the genes themselves have expanded and diversified considerably, particularly within two branches known as class B and class C.

To understand what all this expansion means functionally, the team examined the regulatory regions upstream of each gene and profiled gene activity across heat treatments. Promoter analysis revealed that many lily HSF genes carry binding sites for stress, hormonal and developmental signals, suggesting they do more than simply respond to temperature — they may integrate a wide range of cues, from drought and salinity to growth hormones and flowering time. Transcriptome profiling confirmed that a substantial number of the genes are indeed heat-responsive, ramping up or down when temperatures climb. Among them, one gene stood out: LdHSFC1, a member of the class C branch, which was strongly induced by heat treatment.

That induction might sound like a good sign — a gene waking up to fight the heat — but the team’s functional experiments told a very different story. When they determined where the LdHSFC1 protein operates inside the cell, they found it accumulates in the nucleus, the expected location for a transcription factor. But when they tested its effect on gene expression, LdHSFC1 behaved as a transcriptional repressor, dampening the activity of the genes it contacted rather than activating them. In transient transformation assays in lily, plants carrying the gene showed clearly reduced thermotolerance, wilting under heat conditions that control plants handled better.

The mechanism behind this effect became clear when the researchers traced LdHSFC1’s influence across the heat-response network. Overexpressing LdHSFC1 suppressed the expression of four key protective genes: LdHSFA1, LdHSFA2, LdHSFA3 and LdMBF1c. Silencing the gene, by contrast, enhanced the expression of all four. This matters because HSFA2 is widely regarded as one of the most important positive regulators of acquired thermotolerance in plants — in Arabidopsis, it is required for plants to extend their heat protection after a mild warming episode, and HSFA3 works alongside it in complexes that drive transcriptional memory of heat stress. MBF1c, meanwhile, is a transcriptional coactivator that helps relay heat signals to the defense machinery. By holding these genes down, LdHSFC1 effectively applies a brake to the plant’s entire heat-defense program.

To prove the connection was direct rather than indirect, the team turned to two complementary molecular assays. Yeast one-hybrid experiments showed that the LdHSFC1 protein physically binds to the promoter region of LdHSFA2. Dual-luciferase assays, a standard technique for measuring transcriptional activity, then confirmed that this binding represses LdHSFA2 transcription. Together, the results establish LdHSFC1 as a negative regulator of thermotolerance that acts by directly suppressing the plant’s central heat-response activator — a finding that the authors describe as the first genome-wide overview of the lily HSF family combined with the identification of a clear functional villain in the heat-stress story.

The result is notable because it complicates a simple picture of heat shock factors as uniformly protective. Class B and class C HSFs in other species have shown mixed roles: some, like Arabidopsis HsfB1 and HsfB2b, repress heat-inducible genes yet still contribute positively to acquired thermotolerance, while others, such as rice OsHsfB2b, clearly undermine stress tolerance. In lily itself, earlier work from the same group showed that LlHSFC2 coordinates with class A factors to balance the heat response and actually improve tolerance, and that LdHSFB2a plays its own role in the network. LdHSFC1 now emerges as a class C member with the opposite effect, underscoring how evolutionarily related genes within the same family can evolve sharply divergent functions — and how dangerous it would be to assume that any heat-induced transcription factor is automatically a friend.

Why would a plant evolve a gene that weakens its own heat tolerance? The most likely answer lies in the economics of stress responses. Mounting a full heat-defense program — churning out chaperones, remodelling membranes, adjusting metabolism — is expensive, and plants must balance immediate survival against growth, reproduction and development. Repressors like LdHSFC1 may serve as tuning knobs, preventing the heat response from running too hot and too long when conditions do not warrant it. Under natural conditions this trade-off may be adaptive; under the increasingly extreme temperatures of a changing climate, it can become a liability. Understanding which genes act as brakes, and when, is therefore just as important for breeders as knowing which genes act as accelerators.

The practical implications reach well beyond basic biology. Lilies are among the most valuable cut flowers worldwide, and heat stress during cultivation reduces bloom quality, shortens vase life and narrows the geographic range where commercial growing is viable. The new genome-wide catalogue gives breeders and biotechnologists a complete parts list of lily heat-response regulators, and LdHSFC1 offers an obvious intervention point: silencing or editing the gene, or selecting natural variants with weaker repressor activity, could plausibly produce lilies that hold their blooms through hotter summers. The findings also carry lessons for other ornamental and crop species, where class B and class C HSFs remain underexplored. As the authors note, the work broadens understanding of heat-responsive transcriptional regulation in ornamental plants and highlights potential targets for enhancing lily thermotolerance — a small gene with an outsized role in deciding whether one of the world’s favorite flowers can keep its cool.

Subject of Research: Genome-wide analysis of heat shock transcription factor genes and the role of LdHSFC1 in heat stress tolerance in lily

Article Title: Genome-wide analysis of the HSF gene family in lily and functional characterization of LdHSFC1 under heat stress

Article References: Genome-wide analysis of the HSF gene family in lily and functional characterization of LdHSFC1 under heat stress. (n.d.). https://doi.org/10.1007/s00299-026-03995-3

Image Credits: AI Generated

DOI: 10.1007/s00299-026-03995-3

Keywords: lily, heat shock transcription factors, LdHSFC1, thermotolerance, LdHSFA2, heat stress, genome-wide analysis, transcriptional repressor, Plant Cell Reports, ornamental plants, gene regulation, Lilium