A Versatile Hairy Root Transformation System and Its Application in EjLEC2 Functional Research of Loquat

Loquat (Eriobotrya japonica) regeneration and transformation are difficult, hindering gene function studies. To overcome this limitation, we developed a rapid and stable regeneration and transformation system for hairy roots in loquat by optimising key conditions, in order to explore the potential functions of key genes involved in root growth and development. LEAFY COTYLEDON 2 (LEC2) is a central hub linking embryonic development, lipid synthesis, root system development, and hormonal regulation. However, the role of the LEC2 protein in regulating root growth and development in loquat remains unclear. This study demonstrates a specific interaction between LEC2 and FUSCA3 (FUS3) in loquat, with FUS3 acting downstream of LEC2. Overexpression of LEC2 or FUS3 showed longer root length and increased root numbers, while loss-of-function mutants of either LEC2 or FUS3 exhibited shorter root lengths and reduced root numbers, and overexpression of FUS3 effectively compensated for the root growth defects in LEC2 knockout mutants. In summary, the stable Agrobacterium rhizogenes-mediated transformation system provides an effective approach for gene function analysis and genetic engineering research in loquat, and the LEC2-FUS3 complex functions as a key regulator in auxin-regulated root growth and development.