Genome sequencing, assembly and annotation of the carob tree, Ceratonia siliqua (Eudicots:Fabaceae)

Abstract

The carob tree, Ceratonia siliqua, is an evergreen tree that belongs to the family of Fabaceae. It has been cultivated for thousands of years in Mediterranean countries and thus, has a considerable impact on the nutrition of humans as well as other animals of this region. Despite its importance, genomic resources are still scarce for this plant species. To fill this gap, we undertook the sequencing, assembly and annotation of the carob tree genome, which resulted in the first, nearly chromosome-level assembly for this plant species. The total assembly size is 492 Mbp which is close to the previously estimated genome size. The assembly N50 is 34.99 Mbp, thus showing a high contiguity, which is also evident from the fact that >98% of the assembly is contained in as few as 17 very large contigs. Moreover, both the genome sequence as well as the predicted gene set contain more than 96% of conserved, full-length BUSCOs. Finally, a comparative orthology analysis with 10 other plant species showed that the vast majority of the predicted carob tree genes have orthologs in the other plants and only a small fraction of them appears to be species-specific. Additional analyses are in progress for a more detailed study of the agronomic traits of this important legume.