Identification of the WOX genes in Eucommia ulmoides and functional identification of EuWOX11 in adventitious root formation and plant growth

Eucommia ulmoides is a woody plant with high economic and medicinal value. Currently, the efficiency of its clonal propagation is severely constrained by the low capacity of adventitious root formation and development. WUSCHEL-related homeobox (WOX) transcription factors (TFs) have been widely reported to play critical regulatory functions in adventitious root development in plants. However, systematic characterization of the WOX gene family in E. ulmoides remain insufficient, and its potential function in adventitious root formation are still unclear. In this study, 11 EuWOX genes were identified from the E. ulmoides genome, and their phylogenetic relationships, gene structures, and expression patterns were systematically characterized. Protein sequence analysis and phylogenetic classification revealed that EuWOX11 shares high sequence homologous to AtWOX11 and AtWOX12 from Arabidopsis thaliana , as well as PtWOX12 in Populus trichocarpa . Furthermore, EuWOX11 exhibited a high expression level in the seedling roots of E. ulmoides . To further elucidate its biological function, EuWOX11 was heterologously overexpressed in Populus tomentosa ‘Lumao 50’. Compared with the wild-type (WT), EuWOX11 overespression lines produced a significantly higher number of adventitious root, accompanied by increased of root length and root biomass, as well as promoted vegetative growth. These results demonstrate that EuWOX11 functions as a positive regulator of adventitious root development in P. tomentosa . The functional characterization of EuWOX11 not only reveals its potential application in molecular breeding for improving clonal propagation efficiency of woody plants, but also provides an candidate target for elucidating the molecular regulatory mechanisms underlying adventitious root formation in E. ulmoides .