Transcriptomic analysis reveals differential gene expression patterns during cannabis leaf morphogenesis and phase transition

Understanding the molecular mechanisms governing leaf morphogenesis and phase transition in <i>Cannabis sativa</i> is critical for optimizing its growth, development and yield. In this study, we conducted a comparative transcriptomic analysis to investigate the gene expression patterns associated with leaf development and the transition from vegetative to reproductive phases in cannabis plants. Following germination, cannabis plants display a distinct leaf developmental pattern. While the specific number of leaflets varies among cultivars, here we focused on the White Widow cultivar as a model. It showed an increase in the number of serrated leaflets from one (L1) to nine (L5) in a node-specific manner. Subsequently, the number of leaflets decreased from eight (L6) to three (L9). The transition from vegetative to reproductive phases, marked by the appearance of solitary flowers and a shift from opposite to alternate leaf phyllotaxy, occurred at node 7 and node 12, respectively. Analysis of gene expression revealed 1358 differentially expressed genes, with 1,182 genes showing differential expression across all leaves. Notably, several genes involved in leaf morphogenesis (e.g. <i>YAB</i>, <i>AGO5</i>, and <i>TCP4</i>) were found to be upregulated in compound leaves (L2) compared to simple leaves (L1), implying a role in leaflet formation and overall leaf morphology. Furthermore, several genes associated with phase transition and flowering (e.g. <i>SPLs</i>, <i>ELFs</i>, <i>SOC1</i>, and <i>CEN-Like</i>) exhibited specific expression patterns during the transition from vegetative to reproductive phases. These findings provide valuable insights into the genetic regulation of leaf morphogenesis and phase transition in cannabis.