Genome-wide identification of Rab GTPases in Brassica napus: Expression dynamics indicative of roles in male gametophyte & seed development and in stress responses

As the most prominent family of small guanosine triphosphate (GTP)-binding proteins in plants, RAB GTPases are essential regulators of intracellular trafficking, cytokinesis, autophagy, growth and development, as well as mediators of plant-pathogen interactions and environmental (abiotic and biotic) stress responses. While structurally and functionally characterised in various crops, the RAB GTPase gene family and its functional roles have remained unexplored in allopolyploid canola ( Brassica napus ). This study identified 205 BnRAB (RAB GTPases in Brassica napus ) genes, representing the largest RAB GTPase family reported to date in a eudicot species. Phylogenetic and sequence analyses classified these genes into eight distinct groups (RABA–H), with members within each group exhibiting highly conserved gene structures and protein motif distributions. Evolutionary analysis suggested that the diversity of the BnRAB family may reflect the shared evolutionary history of the Brassica lineage, including ancient whole-genome triplication and subsequent hybridisation of Brassica rapa and Brassica oleracea . Transcriptomic analysis of publicly available RNA-Seq datasets indicates preferential expression of RAB GTPases in reproductive tissues and developing seeds, suggesting their potential roles in regulating agronomically important traits such as pollen development, seed set, and storage compound accumulation, thereby providing candidate targets for improving yield stability and stress resilience in canola. This is further supported by protein domain identification, promoter cis -element profiling and subcellular localisation prediction studies, which together associate these proteins with male gametophyte and seed development, and signalling pathways for light, phytohormones and various biotic (infection with Sclerotinia sclerotiorum , Leptosphaeria maculans , Leptosphaeria biglobosa ) and abiotic (salinity, cold, drought and heat) stresses. These findings are based on computational and transcriptomic analyses, and further research is needed to establish the link between RAB GTPases and agronomically important traits in canola. Collectively, this research provides a comprehensive catalogue of BnRABs, providing a valuable genomic resource for future functional studies investigating the molecular mechanisms that drive plant development and stress tolerance.