The research team, led by Jianhang Zhang and Jiecheng Li with corresponding authors Hongqing Li and Shuai Liao, began with a deceptively simple observation. In nature, Saxifraga stolonifera displays three stable leaf phenotypes: fully green, white-variegated, and purple-variegated. Crucially, these phenotypes show both air space-type variegation, in which microscopic cavities between tissue layers scatter light and create pale patches, and pigment-type variegation, in which colored compounds accumulate unevenly within cells. Most variegated plants rely on just one of these mechanisms. Understanding how a single species orchestrates both at once required a far more comprehensive toolkit than any single sequencing approach could provide.

That toolkit started with the genome itself. The researchers assembled a high-quality, chromosome-scale genome of approximately 2.01 gigabases, confirming a diploid chromosome number of 2n = 36. Comparative genomics revealed that after the ancient gamma-triplication event shared across core eudicots, Saxifraga stolonifera underwent its own recent whole-genome duplication, a doubling that supplied raw genetic material for evolutionary experimentation. The team also identified 155 expanded gene families, and when they examined what those expansions were enriched for, a telling pattern emerged: the duplicated and proliferating genes clustered heavily in flavonoid and phenylpropanoid biosynthesis pathways, the metabolic machinery that plants use to build pigments and protective secondary metabolites. In other words, the plant’s evolutionary history had already primed it for chemical coloration.

To connect that genomic potential to visible color, the researchers turned to metabolomics, cataloguing the small molecules present in the different leaf regions. They detected 58 anthocyanin-related compounds, the water-soluble pigments responsible for reds, purples, and blues across the plant kingdom. Within this chemical library, ten key pigments stood out as the ones responsible for the distinctive purple patches on variegated leaves. Among them were cyanidin-3-O-glucoside, peonidin-3-O-galactoside, and quercetin-3-O-glucoside, each a flavonoid backbone decorated with sugar groups. That decoration is not cosmetic trivia. The attachment of sugar molecules, a process called glycosylation, changes a pigment’s solubility, stability, and where it ends up stored inside the cell, and it proved to be the decisive step in this plant’s coloring scheme.

The enzyme responsible for that decisive step belongs to a family called anthocyanidin 3-O-glucosyltransferases, and the study pinpointed a specific gene, SsBZ1, with two copies annotated as Sst12G009310 and Sst14G006050. In the purple-variegated leaves, these genes were strongly upregulated, and their activity tracked precisely with the accumulation of the ten key glycosylated pigments in the sub-palisade cells, the layer beneath the leaf’s photosynthetic workhorse tissue. The implication is elegant: the purple patches are not simply the result of making more anthocyanin, but of a glycosylation step that determines which pigment forms are produced and where they are deposited. Without SsBZ1-mediated sugar tagging, the flux through the anthocyanin pathway apparently never resolves into the visible purple chemistry that gives the leaves their moody splashes.

White variegation told a completely different story. Rather than pigment, the pale zones on white-variegated leaves arise from anatomy, specifically from air spaces that form between the epidermis and the palisade tissue along the veins. These intercellular cavities reflect and scatter light before it can be absorbed, producing the milky appearance that gardeners prize. When the researchers measured plant hormones across the leaf types, they found that white-variegated leaves accumulate high levels of bioactive gibberellins, specifically GA4 and GA7. Gibberellins are best known as growth-promoting hormones that drive stem elongation and seed germination, but here they appeared to be sculpting leaf architecture from the inside out.

The source of those hormones was traced to a single gene with outsized influence. Gibberellin 3β-dioxygenase, encoded in this species as SsGA3ox (Sst05G017510), catalyzes the final activation step that converts precursor gibberellins into their bioactive forms. Expression of SsGA3ox was elevated in the white-variegated leaves, consistent with the elevated GA4 and GA7 levels. To place this gene in a broader regulatory context, the team performed weighted gene co-expression network analysis, a computational method that groups thousands of genes into modules based on correlated activity across samples. One module, labeled salmon, emerged as gibberellin-associated, and SsGA3ox sat at its center as the hub gene, the most connected and influential member of the network.

What makes the finding conceptually important is the hierarchical model the authors propose from these results. In their framework, gibberellin-driven upstream flavonoid flux is activated in both variegated phenotypes, meaning the hormone system and the pigment precursor pathway are engaged in white and purple leaves alike. But the final visible pigmentation is determined by SsBZ1-mediated glycosylation specificity and by the spatial localization of the resulting compounds. This suggests a possible hierarchical separation between the structural pathway, which builds air spaces and pale zones through cell expansion, and the pigmentation pathway, which fills specific cells with colored glycosides. Two programs, running in parallel and resolved at different points, produce a single integrated pattern on every leaf.

The practical implications reach well beyond one species. Leaf variegation is a major ornamental trait, and breeders have long selected for it without understanding its genetic basis. The integrative omics framework established here, linking genome, metabolome, and transcriptome into a coherent causal model, offers a template for dissecting variegation in other ornamental plants, from hostas to calatheas. The identification of SsBZ1 and SsGA3ox as candidate genes gives molecular breeders concrete targets, whether through marker-assisted selection or eventual genome editing, to stabilize or enhance variegated patterns in horticultural lines. The expanded flavonoid gene families documented in the genome may also hold value for studying pigment chemistry more broadly.

The authors are careful to note the limits of the current work. Functional validation of the identified candidate genes is still required to confirm their precise roles, since co-expression and metabolite correlation, however compelling, do not constitute proof of causation. Future experiments, such as knocking out or overexpressing SsBZ1 and SsGA3ox, will be needed to close that loop. Even so, the study marks a genuine advance: it takes one of botany’s most familiar visual puzzles, the painted leaf, and resolves it into two traceable molecular threads, a sugar-tagging enzyme painting purple patches in the sub-palisade layer and a gibberellin enzyme inflating air spaces along the veins. For a plant long admired for its appearance, Saxifraga stolonifera has finally begun to explain itself, and the explanation is as intricate as the pattern itself.

Subject of Research: Multi-omics dissection of the genetic and biochemical mechanisms underlying leaf variegation in Saxifraga stolonifera

Article Title: Multi-omics reveals divergent regulation of anthocyanin glycosylation and gibberellin biosynthesis underlying leaf variegation in Saxifraga stolonifera

Article References: Zhang, J., Li, J., Xing, H., Zhang, F., Wang, C., Tang, F., Li, H., & Liao, S. (2026). Multi-omics reveals divergent regulation of anthocyanin glycosylation and gibberellin biosynthesis underlying leaf variegation in Saxifraga stolonifera. BMC Genomics. https://doi.org/10.1186/s12864-026-13339-w

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13339-w

Keywords: Saxifraga stolonifera, leaf variegation, anthocyanin glycosylation, gibberellin biosynthesis, SsBZ1, SsGA3ox, whole-genome duplication, metabolomics, transcriptomics, WGCNA, flavonoid biosynthesis, ornamental plants