Potential roles of pseudobulbs in mediating signal responses and hormone translocation during floral bud dormancy release in Pleione bulbocodioides

Pleione bulbocodioides, a world-renowned ornamental orchid, exhibits a pronounced winter dormancy in its floral buds, thereby presenting a spring flowering characteristic. Currently, the mechanisms underlying floral bud dormancy and its release in this orchid remain unclear. In this study, we investigated the regulatory mechanism of floral bud dormancy release in P. bulbocodioides using integrated physiological and transcriptome analysis. We observed that floral bud dormancy in P. bulbocodioides was significantly released within a one-week period, which was accompanied by a sharp decrease in abscisic acid (ABA) content and a simultaneous increase in gibberellin (GA) content and the GA/ABA ratio in both floral buds and pseudobulbs. Importantly, the levels of these hormones are significantly higher in the pseudobulbs than in the corresponding buds. Transcriptomic analysis identified ABA2-2 (transcript_30713) and GA20ox (transcript_29841) as key genes involved in ABA and GA biosynthesis, respectively. Furthermore, we speculate that pseudobulbs may serve as critical hubs for signal perception and hormone redistribution, supplying buds with phytohormones via transporters such as ABCGs and NPFs. This transport process is potentially regulated by day-length signaling, mediated by CONSTANS (CO) and phytochrome A (PHYA). Our results provide valuable insights into the key internal factors involved in floral bud dormancy release in Pleione species, and highlight the potential role of pseudobulbs in this process, thereby providing a theoretical basis for manipulating flowering time in this genus.