Grafting is a practical way to propagate elite trees, especially varieties with desirable wood quality but poor rooting ability. In woody plants, however, the partnership between rootstock and scion remains hard to decode because water, nutrients, hormones, proteins, metabolites and RNA molecules may all travel through vascular tissues. Mobile messenger ribonucleic acid (mRNA) has been studied more widely, but mobile long non-coding ribonucleic acid (lncRNA) is less understood, particularly in trees, where long life cycles and complex genomes make experiments difficult. Based on these challenges, there is a need to carry out in-depth research into how mobile RNAs and metabolic pathways cooperate to regulate growth in grafted woody plants.
A research team from the Institute of Forest Biotechnology, Forestry College, Agricultural University of Hebei, and the Hebei Key Laboratory for Tree Genetic Resources and Forest Protection published (DOI: 10.1093/hr/uhag086) the study on March 11, 2026, in Horticulture Research. The study used Populus × euramericana cultivar ‘Neva’ (poplar 107) as the rootstock and Populus tomentosa ‘Yixian’ as the scion, combining physiological measurements, transcriptome sequencing, metabolomics and mobile RNA identification to explain how a vigorous rootstock regulates scion growth in a woody grafting system.
Compared with self-grafted Populus tomentosa, heterografted scions on poplar 107 were taller and had higher net photosynthetic rates. Metabolomic profiling detected 3,036 metabolites and showed that the rootstock shifted scion metabolism toward carbon fixation, carbon metabolism and cell-structure-related pathways, while reducing pathways linked to respiration and defense. This matched the observed rise in photosynthetic performance. Transcriptome analysis identified 2,913 differentially expressed mRNAs and 345 differentially expressed lncRNAs in scions, suggesting that lncRNA-based regulation is part of the growth response. The team also found extensive RNA movement across the graft junction: 118 mRNAs and 14 lncRNAs moved upward from rootstock to scion, while 487 mRNAs and 94 lncRNAs moved downward from scion to rootstock. Mobile mRNA-associated genes were mainly linked to amino acid metabolism, whereas mobile lncRNA-associated genes were enriched in energy metabolism. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) supported the mobile RNA identification with an 85% validation rate. Integrated transcriptome–metabolome analysis then singled out flavonoid biosynthesis as a shared pathway, and the gene POTOM_056827 was positively associated with kaempferol accumulation. In Nicotiana benthamiana, root-applied kaempferol increased height gain, leaf area and photosynthetic capacity, while reducing reactive oxygen species (ROS) indicators, including hydrogen peroxide (H₂O₂), superoxide anion (O₂−) and malondialdehyde (MDA).
The authors said the study begins to show how a rootstock can influence a scion not only by supplying water and minerals, but also by sending molecular information. They said poplar 107 appears to help the scion capture more carbon, spend less energy on defense-related metabolism and strengthen antioxidant protection. They also said the contrasting roles of mobile mRNAs and lncRNAs provide a useful framework for studying grafting in woody plants, where long-distance signaling has been difficult to track and even small molecular shifts can shape growth.
These findings could help guide rootstock selection in poplar propagation and other woody plant improvement programs. For Populus tomentosa, whose excellent trunk form and wood quality are limited by poor rooting ability, pairing with an easy-to-root rootstock such as poplar 107 may improve early growth and production efficiency. The work also points to mobile RNAs and kaempferol-related flavonoid metabolism as candidate markers or targets for future breeding and nursery management. It may help breeders screen rootstock–scion pairs before large field trials. Because the kaempferol test was performed in an herbaceous model plant, further studies in woody species will be needed. Even so, the study moves grafting closer to a predictive tool for improving tree vigor.
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References
DOI
10.1093/hr/uhag086
Original Source URL
https://doi.org/10.1093/hr/uhag086
Funding information
This study was supported by the Major Project of Agricultural Biological Breeding (2022ZD0401502) and The Province Key Research and Development Program of Hebei (Grant No. 21326301D).
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.