An Integrative morphology-hormone-transcriptome analysis of uniconazole induced internode shortening in Paeonia lactiflora.

Plant height represents a critical ornamental trait in Paeonia lactiflora. While uniconazole has been demonstrated to effectively modulate plant height in this species-enhancing its ornamental value and supporting commercial production-the molecular mechanisms responsible for uniconazole-induced dwarfism remain largely elusive. In this study, we employed an integrated approach combining morphological, physiological, cytological, and molecular analyses to elucidate the dwarfing mechanism in P. lactiflora 'Dafugui'. Our results indicate that uniconazole treatment significantly suppressed internode elongation, reduced cell length, and decreased active gibberellin content. Notably, although exogenous GA4 application elevated endogenous GA4 levels, it exerted negligible effects on plant height, internode elongation, and cell length, suggesting a marked reduction in gibberellin sensitivity in the dwarf phenotype. Integrated transcriptomic and morphological profiling revealed consistent downregulation of the gibberellin receptor gene GID1 and the positive regulatory F-box gene GID2 across four developmental stages under uniconazole treatment. Conversely, the DELLA family negative regulator GAI was persistently upregulated. These findings implicate GID1, GID2, and GAI as pivotal regulators of plant height architecture. Subsequent functional validation in Arabidopsis thaliana confirmed that overexpression of PlGID1b and PlGID2 promoted plant height and cell elongation, whereas overexpression of PlGAI resulted in reduced plant height and shorter cells, underscoring their essential roles in cell expansion and internode development. Collectively, this study provides fundamental insights into the regulatory network underlying uniconazole-mediated dwarfism and offers valuable genetic tools for the molecular breeding of plant architecture in P. lactiflora.