Scientists identify dual-control gene that shapes pear fruit color during ripening

A pear's skin tells a story written in pigment. As the fruit ripens, red fades and green persists—a transformation so ordinary that few stop to ask why it happens. Scientists at Sichuan Agricultural University have now identified the molecular switch that orchestrates this shift, and it turns out to be far more elegant than anyone expected. The answer is a single gene regulator called PbrMYBL4, which does not simply control one color pathway but manages two at once, suppressing the production of red anthocyanin pigments while simultaneously slowing the breakdown of green chlorophyll. The discovery, published in Horticulture Research on April 17, 2026, reveals how a single upstream controller can coordinate the complex choreography of fruit ripening.

Fruit color matters in ways both practical and profound. It signals to consumers when a pear is ready to eat, and it shapes the market value of the crop. Yet the science of how that color emerges has long been fragmented. Researchers have identified many genes and proteins that influence either red pigment accumulation or green pigment loss, but they have typically studied these processes in isolation. The question of whether one master regulator might orchestrate both pathways simultaneously remained largely unexplored—particularly pressing for pear breeders, since red-skinned pear varieties are scarce and genetically unstable, making them difficult to work with in conventional breeding programs.

The team working with the red-striped cultivar 'Red Zaosu' began by mapping how pigments changed as the fruit developed. They tracked gene expression across different ripening stages and noticed that PbrMYBL4, an R2R3-MYB transcriptional repressor, showed a striking pattern: its levels rose precisely as chlorophyll was retained and anthocyanin declined. To test whether this correlation reflected genuine causation, they ran a series of experiments. When they artificially increased PbrMYBL4 in pear tissue, red pigmentation dropped and green color persisted. When they silenced the gene using RNA interference, the opposite occurred—more red, less green. The same dual effect held up across multiple experimental systems: transient overexpression in pear fruit, stable transformation in pear cell cultures, and even heterologous expression in tobacco plants.

The molecular mechanics proved intricate. Using techniques including dual-luciferase assays, yeast one-hybrid analysis, and electrophoretic mobility shift assays, the researchers mapped exactly how PbrMYBL4 exerts its control. On the red-pigment side, the gene works through multiple layers. It directly binds to and represses structural genes involved in anthocyanin synthesis, such as PbrF3H and PbrANS. But it also targets PbrMYB10b, a key activator gene that normally drives the entire anthocyanin pathway. By weakening this upstream activator, PbrMYBL4 amplifies its suppressive effect. The mechanism involves protein-protein interaction: PbrMYBL4 physically binds to PbrbHLH3, a protein that normally partners with PbrMYB10b to activate anthocyanin genes. This binding competition disrupts the activating complex, further dampening red pigment production. On the green-pigment side, PbrMYBL4 directly binds the promoter of PbrSGRL, a gene that promotes chlorophyll breakdown. By reducing PbrSGRL transcription, the regulator slows the loss of green color.

What makes this discovery significant is not simply the identification of another color-related transcription factor. Rather, it is the demonstration that one regulator can directly connect two pigment programs that jointly determine the final appearance of the fruit. The authors emphasize that PbrMYBL4 achieves this coordination through distinct molecular routes—one targeting anthocyanin biosynthesis at multiple levels, the other directly inhibiting chlorophyll degradation—yet both serve the same developmental purpose. This framework helps explain the characteristic red-to-yellowish-green transition seen in 'Red Zaosu' and provides a clearer molecular picture of how complex fruit-color patterns emerge during ripening.

The practical implications for breeding are substantial. Instead of selecting independently for high anthocyanin intensity and rapid chlorophyll loss—a laborious process requiring multiple crosses and generations—breeders might eventually manipulate this single shared control point to stabilize coloration, intensify certain hues, or create entirely new visual traits. The discovery also suggests that similar dual-function regulators may exist in other horticultural crops, potentially opening new avenues for color engineering across the produce industry. However, the path from laboratory to orchard remains cautious. The authors note that PbrMYBL4 overexpression disrupted normal flowering and fruiting in tobacco, a warning that manipulating this regulator could have unintended consequences on fruit development, yield, and other quality traits. Validation in stable pear lines across diverse genetic backgrounds, along with careful assessment of broader developmental effects, will be necessary before breeders can reliably deploy this knowledge in the field.