Apple trees and other perennial woody plants face persistent agronomic challenges due to their sparse root systems, which reduce nutrient acquisition efficiency and weaken stress responses. Under drought conditions, rootstocks with poor root vigour show significantly reduced expression of key stress‑response genes, and severe drought can push yield efficiency below 40 % while increasing plant mortality to 60 %. very‑long‑chain fatty acids (VLCFAs)—fatty acids with acyl chains over 18 carbons—are known to regulate root development in herbaceous plants such as Arabidopsis, where they influence lateral root spacing and pericycle cell proliferation. However, their role in woody plants, particularly apple, has remained completely unknown. Due to these challenges, there is an urgent need for in‑depth research into the molecular mechanisms that govern root development in apple and other woody fruit trees.
Now, researchers from the National Research Center for Apple Engineering and Technology at Shandong Agricultural University in China have identified a key regulatory pathway that controls root morphogenesis in apple. Published (DOI: 10.1093/hr/uhag168) in the journal Horticulture Research in 2026, the study demonstrates that a lipid transfer protein called MdLTPG17 and a fatty acid synthase called MdKCS19 work together under the control of the transcription factor MdARF19 to modulate VLCFAs accumulation and promote root elongation.
The team found that exogenous application of VLCFAs to apple seedlings significantly increased root length and surface area while elevating auxin (IAA) levels in roots—an effect achieved through both enhanced IAA biosynthesis and suppressed IAA degradation. They then demonstrated that MdLTPG17, a glycosylphosphatidylinositol‑anchored lipid transfer protein previously shown to transport cuticular wax components, promotes root elongation when overexpressed. Through yeast two‑hybrid screening, the researchers identified MdKCS19—a β‑ketoacyl‑CoA synthase involved in VLCFAs chain elongation—as an interacting partner of MdLTPG17. Both proteins were found to be direct transcriptional targets of MdARF19, which binds to auxin response elements in their promoters. Transgenic apple roots co‑overexpressing MdARF19, MdLTPG17 and MdKCS19 showed the greatest enhancements in root length and surface area, while double‑silenced lines exhibited the most severe reductions. Lipidomic analysis further pinpointed C18:0‑OH as a primary VLCFAs component driving root elongation in apple—a finding that contrasts with longer‑chain VLCFAs previously implicated in Arabidopsis root development, revealing both conservation and divergence in root system evolution across species.
“For years, we’ve known that auxin is central to root development, but our work shows that VLCFAs are not just passive structural components—they are active players in a regulatory network that amplifies auxin signals in roots,” the authors said. “What’s particularly exciting is that the specific fatty acid driving this effect in apple is C18:0‑OH, a shorter‑chain component, rather than the longer‑chain wax compounds that function in Arabidopsis. This tells us that while the core regulatory logic is conserved across plant species, the molecular players have adapted to meet the specific needs of woody perennials.”
These findings have significant implications for apple breeding and orchard management. By identifying MdARF19, MdKCS19 and MdLTPG17 as key regulators of root architecture, the study provides candidate genes for genetic improvement of root systems in apple and potentially other woody fruit trees. Enhanced root density could improve iron uptake under alkaline soil conditions—where sparse‑rooted plants show a 50 % reduction in active iron—and boost drought tolerance by strengthening stress signalling pathways. The results also open new avenues for CRISPR‑Cas9‑based engineering of root traits and for developing more resilient rootstocks that can maintain productivity under challenging environmental conditions. Ultimately, this research offers a roadmap for translating fundamental discoveries about lipid‑auxin crosstalk into practical solutions for sustainable fruit production.
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References
DOI
10.1093/hr/uhag168
Original Source URL
https://doi.org/10.1093/hr/uhag168
Funding information
This work was supported by the National Key Research and Development Program of China (2023YFD2301000), the National Key Research and Development Program of Shandong Province (2024CXGC010903, 2023CXPT013), the China Agriculture Research System of apple (CARS‑27), the National Natural Science Foundation of China (32472705, 32302513), the Young Talent of Lifting engineering for Science and Technology in Shandong (SDAST2024QTA083), and the Natural Science Foundation of Shandong Province (ZR2022JQ14, ZR2022QC112).
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.