Functional insights into a putative 2-OG oxygenase involved in jasmonic acid metabolism and xylem development in <i>Populus trichocarpa</i>

The xylem vascular tissue constitutes an efficient system of long-distance transport of water and nutrients, as well as structural support to the plant body. Despite its importance, the molecular mechanisms regulating xylogenesis remain only partially understood. In this study, we investigated two genes from Populus trichocarpa, encoding 2-oxoglutarate and Fe(II)-dependent oxygenases, whose expression is significantly upregulated during secondary growth. Proteins encoded by those genes share similarities with Arabidopsis enzymes known as jasmonic acid oxygenases (JAOs) or jasmonate-induced oxygenases (JOXs), which are involved in the hydroxylation of jasmonic acid (JA) - a hormone precursor critical for plant development and stress responses. We hypothesized that the Populus 2-OG oxygenases participate in JA metabolism and thereby influence wood formation. Their in silico structural analysis indicated that one of these proteins likely binds JA with similar efficiency to known JAO proteins. A link was supported by in vitro and in vivo experiments. Studies in an Arabidopsis JAO-depleted mutant revealed altered stem anatomy, characterized by a reduced stem diameter and an increased proportion of xylem area relative to the total stem cross-section, suggesting that disrupted JA metabolism can interfere with normal vascular development. These findings provide new insights into the hormonal regulation of vascular development and may have practical implications for improving wood quality or stress resilience in trees.