\"GPress: a framework for querying General Feature Format (GFF) files and feature expression files in a compressed form\"

Abstract

11.1 MotivationSequencing data are often summarized at different annotation levels for further analysis. The general feature format (GFF) and its descendants, the gene transfer format (GTF) and GFF3, are the most commonly used data formats for genomic annotations. These files are extensively updated, queried and shared, and hence as the number of generated GFF files increases, efficient data storage and retrieval are becoming increasingly important. Existing GFF utilities for accessing these files, like gffutils and gffread, do not focus on reducing the storage space, significantly increasing it in some cases. Hence, we propose GPress, a framework for querying GFF files in a compressed form. In addition, GPress can also incorporate and compress feature expression files, supporting simultaneous queries on both files.\n\n1.2 ResultsWe tested GPress on several GFF files of different organisms, and showed that it achieves on average a 98% reduction in size, while being able to retrieve all annotations for a given identifier or a range of coordinates in a few seconds. For example, on a Human GFF file, GPress can find all items with a unique identifier in 2.47 seconds and all items with coordinates within the range of 1,000 to 100,000 in 4.61 seconds. In contrast, gffutils provides faster retrieval but doubles the size of the GFF files. When additionally linking an expression file, we show that GPress can reduce the size of the expression file by more than 92%, while still retrieving the information within seconds. GPress is freely available at https://github.com/qm2/gpress.