The study, published in Plant Cell Reports, set out to answer two intertwined questions. First, where did a family of plant stress genes known as ERF-VII come from in the deep history of plant evolution? Second, what do these genes actually do in the tea plant when the temperature drops? To resolve both, the researchers combined broad comparative genomics across 14 plant lineages with detailed analyses of 20 tea plant cultivars, creating one of the most comprehensive portraits of this gene family in any woody beverage crop.

The ERF-VII family belongs to the larger AP2/ERF superfamily of transcription factors, master regulators that bind specific DNA sequences and switch suites of target genes on or off. In the model plant Arabidopsis thaliana, ERF-VII proteins are famous for their role in oxygen sensing: they carry a conserved N-terminal motif, the MCGGA/I motif, that tags them for destruction by the oxygen-dependent branch of the N-degron protein degradation pathway. When oxygen is scarce, as during flooding or submergence, these proteins escape degradation, accumulate in the nucleus and activate survival programs. The new work shows that this regulatory architecture is ancient and evolutionarily telling.

By reconstructing phylogenetic trees of ERF-VII proteins across lineages ranging from algae to flowering plants, the team found that the family originated after the divergence of vascular plants, and that its emergence coincided precisely with the appearance of the MCGGA/I motif linked to oxygen-dependent degradation. This suggests that the oxygen-sensing capacity of ERF-VII factors was built into the family at its inception. Gymnosperms, the conifers and their relatives, retained only a few conserved members, while angiosperms underwent dramatic, lineage-specific expansion. Monocots, the grasses and their kin, expanded the family extensively, apparently driven by whole-genome duplication events, whereas eudicots showed more moderate expansion accompanied by functional diversification, with duplicated genes taking on specialized roles in stress and development.

With the evolutionary framework established, the researchers turned to the tea plant itself. A pan-genome analysis, comparing genome sequences from 20 different tea cultivars, revealed that the ERF-VII gene complement is not identical across varieties. Some cultivars carry genes that others lack, and the family members fall into categories that differ in number and distribution between accessions. This varietal variation is significant because it provides raw material for breeders: genes present in hardy landraces but absent or divergent in elite cultivars could underpin differences in freezing tolerance that breeders can exploit through marker-assisted selection.

To identify which ERF-VII members respond to cold, the team mined transcriptome data from the Tea Plant Information Archive, a public repository of gene expression profiles. One member, named CsRAP2.2, stood out. Its expression was strongly induced by low temperature and, crucially, remained sustained throughout cold treatment rather than flickering briefly and fading. The name is telling: CsRAP2.2 is an ortholog of Arabidopsis RAP2.2, a factor previously implicated in hypoxia survival and low-oxygen, oxidative and osmotic stress responses. The tea version appears to have been recruited into the cold-response network, hinting at an evolutionary link between oxygen sensing and chilling tolerance in this species.

Correlation alone does not prove function, so the researchers ran a series of direct tests. When they silenced CsRAP2.2 in tea leaves, the plants became measurably more vulnerable to cold. Conversely, when they overexpressed the gene in tea leaves and introduced it heterologously into Arabidopsis, both systems showed enhanced cold tolerance. The physiological basis of this protection was traced to three pillars of cellular defense. Transgenic and overexpressing material maintained photosystem II efficiency, the quantum engine of photosynthesis that cold typically damages; they suffered less membrane lipid peroxidation, the oxidative rancidity of cellular membranes that accompanies freezing injury; and they showed improved antioxidant capacity, the enzymatic and chemical scavenging of reactive oxygen species that otherwise accumulate as toxic byproducts of cold stress.

To place CsRAP2.2 within the wider regulatory landscape, the team applied weighted gene co-expression network analysis, a computational method that clusters thousands of genes into modules based on coordinated expression across samples and conditions. This analysis positioned CsRAP2.2 as a hub, a highly connected node integrating cold signaling, hormone pathways and oxygen-sensing machinery. Gene Ontology enrichment of its co-expressed network highlighted processes ranging from protein transport to the detection of oxygen and hypoxia, consistent with the idea that cold, hormone and low-oxygen signals converge on ERF-VII factors in tea. In practical terms, CsRAP2.2 may act less like a lone switch and more like a control tower, coordinating multiple stress-response programs simultaneously.

The broader implications extend well beyond tea biology. Global tea production is concentrated in subtropical and highland regions where frost events are becoming increasingly erratic as the climate shifts. A validated cold-tolerance gene with demonstrated function in both tea and a heterologous model gives breeders a concrete molecular target. Marker-assisted breeding or genome editing approaches could introduce or amplify favorable CsRAP2.2 alleles in susceptible cultivars, potentially protecting harvests without the long timelines of conventional crossing. The pan-genome perspective adds another layer: because ERF-VII gene content varies among cultivars, screening germplasm collections for the most protective variants becomes a tractable strategy.

The study also enriches our understanding of transcription factor family evolution. By anchoring the origin of ERF-VII genes to the rise of vascular plants and tying it to a specific protein motif, the work illustrates how a single molecular innovation, a degron recognized by the N-end rule pathway, can seed an entire regulatory system that plants later repurposed for drought, flooding, hypoxia and now cold tolerance. For the humble tea bush, it seems, survival in the cold may hinge on an ancient oxygen-sensing trick repurposed by millions of years of evolution. For the scientists and growers betting on climate-resilient agriculture, CsRAP2.2 offers a promising lead, and possibly the genetic key to keeping the world’s favorite infusion flowing through frosts to come.

Subject of Research: Evolution and cold-stress function of the ERF-VII gene family in tea plant (Camellia sinensis)

Article Title: Genome-wide identification and evolutionary analysis of the ERF-VII gene family in the tea plant (Camellia sinensis) and functional characterization of CsRAP2.2 in response to cold stress

Article References: Huang, Q., Pan, R., Wu, L., Chen, S., Hu, J., Long, Z., Zhao, J., Hao, X., & Tang, H. (2026). Genome-wide identification and evolutionary analysis of the ERF-VII gene family in the tea plant (Camellia sinensis) and functional characterization of CsRAP2.2 in response to cold stress. Plant Cell Reports, 45(10), Article 290. https://doi.org/10.1007/s00299-026-03973-9

Image Credits: AI Generated

DOI: 10.1007/s00299-026-03973-9

Keywords: tea plant, Camellia sinensis, ERF-VII, CsRAP2.2, cold stress, transcription factors, pan-genome, oxygen sensing, N-degron pathway, plant evolution, molecular breeding, abiotic stress