On May 23, 2025, a research team from the Fruit Research Institute of Guangdong Academy of Agricultural Sciences published a paper titled "Establishment of an efficient Agrobacterium rhizogenes-mediated hairy root transformation method for subtropical fruit trees" in Horticultural Plant Journal.
As a core technology in the field of plant genetic engineering, Agrobacterium tumefaciens-mediated genetic transformation has established a mature application system in herbaceous plants such as Arabidopsis and tobacco, laying a solid foundation for gene function research and crop genetic improvement. However, this technology still faces many bottlenecks in the genetic transformation system of perennial fruit trees: on the one hand, woody plants grow slowly and can only obtain seeds after the juvenile stage; on the other hand, the sensitivity of lignified tissues to Agrobacterium infection is reduced, resulting in significantly lower genetic transformation efficiency than herbaceous model plants. This double dilemma has greatly delayed the progress of fruit tree functional genomics research.
The A. rhizogenes-mediated hairy root transformation system provides a new strategy to overcome this technical problem, but it still faces special challenges in subtropical fruit tree research. Most of these fruit tree seeds are recalcitrant seeds. Their physiological characteristics of being intolerant to dehydration and sensitive to low temperatures make it impossible to effectively preserve them using conventional low-temperature storage technology. At the same time, the existing hairy root transformation technology is highly dependent on a large number of sterile seedlings as transformation receptors, and the unstable seed yield makes it difficult to continuously and stably supply sterile seedling materials, further exacerbating the difficulty of constructing the transformation system and becoming a key constraint on the genetic transformation research of subtropical fruit trees.
In order to break through the limitation of recalcitrant seeds, the authors developed a new method for genetic transformation of hairy roots that does not rely on seed germination, thereby solving the high dependence of the existing transformation system on seeds and providing a new path for genetic research of subtropical fruit trees.
Construct an efficient, convenient and universally applicable A. rhizogenes-mediated hairy root transformation system, which can be adapted to a variety of fruit tree varieties, overcome the current problems of low efficiency and complex operation of hairy root genetic transformation of fruit trees, and promote the rapid development of gene function research and genetic improvement of fruit trees.
Without tissue culture, the hairy root transformation system was successfully established by directly inoculating A. rhizogenes in the ring-barking wounds of living litchi branches and combining the RUBY visual reporter gene.
In addition, the ring-barking method only caused slight damage to the branches, with low branch mortality, and the branches can be reused in theory.
Figure 1. Simple and effective transformation methodology for subtropical fruit trees. (Yin, et al., 2025)
This study developed an efficient A. rhizogenes-mediated hairy root transformation system, which innovatively uses branches as explants and can be widely used in the genetic transformation of hairy roots of woody fruit trees such as litchi, longan, citrus and mango.
This study successfully broke through the technical barriers of traditional genetic transformation that relies on seed germination by establishing a non-seed-dependent hairy root transformation system, providing an important reference for the genetic transformation of hairy roots in other woody or recalcitrant seed plants.
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