miR172-AP2 Controls Age-Dependent Regeneration Competence in Populus.

Plants maintain remarkable regenerative potential, yet this capacity declines with developmental age, limiting clonal propagation and biotechnological applications. Here, we show that the miR172-AP2 module serves as a central determinant of regeneration competence in Populus. Regenerative capacity declines progressively along the shoot developmental gradient, correlating with elevated miR172 and reduced AP2 transcript levels. Functional analyses demonstrate that AP2 promotes both shoot and root regeneration by directly activating downstream transcriptional programmes, including AINTEGUMENTA-LIKE1, BIG LEAF and LIKE APETALA1, which regulate organogenic growth and developmental competence. Elevated miR172 or cytokinin signalling represses AP2, reducing regenerative outcomes, indicating that hormonal and developmental signals converge on this module. Genome-wide analyses reveal that AP2 coordinates a broad network of genes controlling wound response, hormone signalling and cell fate specification. Notably, enhanced regeneration via AP2 occurs without detectable developmental abnormalities, highlighting the practical potential of this module. Collectively, these findings uncover a mechanistic link between developmental phase identity and regeneration, revealing a conserved regulatory module that may be leveraged to enhance regeneration across plant species, with broad implications for propagation, tissue culture and biotechnology.