Root meristem growth factors (RGFs), a class of small peptide hormones that help shape plant roots, may offer a new route to designing better apple rootstocks. By tracing the RGF gene family across 64 plant species and testing its function in apple, researchers found that the family emerged in canonical form in ferns, later contracted and expanded, and diversified markedly within Malus. In apple, the gene MdglRGF1 acted as a brake on adventitious root formation: increasing its expression reduced rooting, while silencing it promoted stronger root growth. The work connects the deep evolutionary history of peptide signaling with a practical target for controlling root architecture in graft-propagated fruit trees.
Apple production depends heavily on grafting, making rootstock traits central to water and nutrient uptake, stress resilience, and orchard performance. Small secreted peptides are increasingly recognized as developmental signals, and root meristem growth factor peptides are known to regulate root meristems and root-system architecture in model plants. Yet their evolutionary origin, natural variation across apple germplasm, and functions during adventitious rooting in woody fruit crops have remained poorly resolved. The availability of a Malus pan-genome now makes it possible to compare these genes across wild and cultivated apples while linking sequence diversity to biological function. Given these challenges, deeper investigation is needed into how Root meristem growth factors (RGFs) evolution and signaling shape apple root regeneration and architecture.
Published (DOI: 10.1093/hr/uhag151) online on April 28, 2026, in Horticulture Research , the study was conducted by researchers from the College of Life Sciences at Shandong Agricultural University, the College of Biology and Oceanography at Weifang University, and the College of Biology and Brewing Engineering at Taishan University. The team combined pan-species comparative genomics, Malus pan-genome analysis, peptide treatments, transgenic experiments, transcriptomics, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) to map RGFs evolution and determine how MdglRGF1 influences primary, lateral, and adventitious root development in apple.
The researchers first built a pan-species small secreted peptide library spanning 64 plants and identified 495 RGF genes. Phylogenetic analysis indicated that canonical RGFs with complete secretory signal features arose in ferns, followed by contraction and renewed expansion during plant evolution. Within 32 Malus accessions, they identified 334 RGF family members grouped into 12 clades. Cultivated apples showed contraction of the family relative to wild apples, while gene copy number differed significantly among ploidy groups, suggesting an association between RGF expansion and polyploidization.
The team then focused on the root-enriched gene MdglRGF1 , which encodes the mature peptide DYTPARKKPPIHN. In Malus hupehensis var. pingyiensis seedlings, exogenous peptide treatment produced a biphasic effect on primary-root growth and progressively suppressed lateral-root density; tyrosine sulfation strengthened these effects. In ‘Gala’ apple, overexpression of MdglRGF1 produced fewer and shorter adventitious roots, whereas RNA interference (RNAi)-mediated silencing promoted rooting. Transcriptome profiling identified 1,714 upregulated and 2,187 downregulated genes in overexpression roots, while expression analyses linked MdglRGF1 activity to altered auxin biosynthesis and transport, suggesting that the peptide reshapes auxin homeostasis during adventitious rooting.
The authors said, “Our results connect the evolution of RGF peptide signaling with a root-development function that is directly relevant to apple propagation. MdglRGF1 does not simply switch root growth on or off; its effects depend on peptide dose, developmental context, and gene activity. By combining pan-genome analysis with functional experiments, we can begin to see how naturally varying peptide-signaling systems may be used to tune root architecture. This gives us a clearer genetic and molecular framework for future rootstock improvement.”
The findings point to two complementary applications. First, the pan-species peptide library and Malus RGF catalog provide resources for discovering small signaling peptides and selecting alleles associated with desirable root traits. Second, MdglRGF1 offers a candidate target for breeding or biotechnology aimed at improving adventitious rooting and shaping root-system architecture in apple rootstocks. The authors also propose that carefully optimized peptide treatments could eventually provide a non-genetic way to influence root growth, although field-scale effectiveness and long-term responses still require testing. More broadly, the study suggests that peptide signaling may become a useful layer in rootstock design, alongside conventional breeding and genomic selection, particularly for orchards facing water, nutrient, and environmental constraints.
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References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhag151
Funding information
This research was financially supported by Key R&D Program of Shandong Province (2025LZGC005), the Taishan Program of Shandong Province (grants tsqn202408127), and the National Natural Science Foundation of China (32372659 and 31972357).
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.
Horticulture Research
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Pan-species genome-wide evolution of the RGF peptide gene family and its impact on adventitious root regeneration in apple
28-Apr-2026
The authors declare that they have no competing interests.