The LmWRKY114-LmGA20ox1 regulatory module promotes stem growth and secondary xylem development in poplar

Gibberellins serve as master regulators of plant growth and development by coordinating growth-related physiological and developmental processes. Gibberellin 20-oxidase (GA20ox), an indispensable rate-limiting enzyme in gibberellin biosynthesis, modulates endogenous gibberellin levels, thereby influencing plant height. However, systematic studies on the function of GA20ox in Lonicera maackii remain limited. Here, we introduced LmGA20ox1 into tobacco and demonstrated that LmGA20ox1 localized to both the cytoplasm and nucleus. Then, we transformed LmGA20ox1 into 84 K poplar ( Populus alba × Populus tremula var. glandulosa ) by genetic transformation. Under both constitutive (35S) and xylem-preferential DX15 promoter (DX15) regulatory control, LmGA20ox1 overexpression led to significant increases in plant height, lignin content, and endogenous gibberellic acid 3 (GA 3 ) levels in stems compared to WT plants at 3 months. Compared to WT, xylem development was enhanced and the vascular layer was significantly increased in these transgenic lines. Yeast one-hybrid (Y1H) and dual-luciferase reporter assays showed conclusively that LmWRKY114 transcriptionally regulated LmGA20ox1 by binding to its promoter. Overall, our results reveal that LmGA20ox1 promotes stem elongation and secondary xylem development in poplar and is transcriptionally controlled by LmWRKY114 , deciphering the molecular basis of GA-regulated growth in woody plants.