Marthe, N. | Search bioRxiv

bioRxiv2025

GraTools, an user-friendly tool for exploring and manipulating pangenome variation graphs

BackgroundPangenome variation graphs (PVGs), which represent genomic diversity through multiple genomes alignment, are powerful tools for studying genomic variations in populations. However, current tools often lack integration, efficiency, or require format conversions, to use them, hindering their usability. ResultsHere, we introduce GraTools, a member of the GraSuite [1], and a fast and user-friendly command-line tool for manipulating PVGs using the original GFA file. After a one-time graph import, GraTools enables rapid subgraph extraction, FASTA sequence retrieval, and comprehensive analyses, including core/dispensable genome ratio calculation or group-specific segment identification. The import step results in conversion in standard data formats (BAM/BED), enabling the reuse of well-optimized existing tools, allowing an efficient storage and the querying of the PVGs large complex data structures. Scalability is ensured by a modular architecture supporting parallel processing and asynchronous I/O operations. GraTools supports coordinates defined on both the primary reference as well as from alternative genomes within the graph without re-import, and its outputs can be easily visualized or manipulated using external tools. Using an Asian rice pangenome graph (13 accessions), we demonstrate its ability to easily extract subgraphs, compute depth statistics, and identify subspecies-specific segments. An intuitive command-line interface, a real-time execution feedback and a detailed logging system make this tool suitable for a wide range of applications, from population genetics to breeding and genomic medicine, for both biologists and bioinformaticians. ConclusionsThrough its unified graph manipulation interface, GraTools offers an interesting alternative to the few existing tools for manipulating PVGs, facilitating rapid, efficient and flexible downstream analyses. It is available as an open-source tool (GNU GPLv3), with its documentation available at https://gratools.readthedocs.io.

bioinformatics↗

bioRxiv2025

GrAnnoT, a tool for effecient and reliable annotation transfer through pangenome graph

The increasing availability of genome sequences has highlighted the limitations of using a single reference genome to represent the diversity within a species. Pangenomes, encompassing the genomic information from multiple genomes, thus offer a more comprehensive representation of intraspecific diversity. However, pangenomes in form of a variation graph often lack annotation information and tools for, which limits their utility for downstream analyses. We introduce here GrAnnoT, a tool designed for an efficient and reliable integration of annotation information in such variation graphs. It projects existing annotations from a source genome to the variation graph and subsequently to other embedded genomes. GrAnnoT was benchmarked against state-of-the-art tools on pangenome variation graphs and linear genomes from Asian rice, and tested on human and E. coli data. The results demonstrate that GrAnnoT is consensual, conservative, and fast. It provides informative outputs, such as presence-absence matrices for genes, and alignments of transferred features between source and target genomes, helping in the study of genomic variations and evolution. GrAnnoTs robustness and replicability across different species make it a valuable tool for enhancing pangenome analyses. GrAnnoT is available under the GNU GPLv3 licence at https://forge.ird.fr/diade/dynadiv/grannot.

bioinformatics↗