Distribution of the Bathycoccus BOC1 orthologous genes in the genome of several other green alga species. (a-d) Bathycoccus BOC1 orthologous genes in the genomes of Ostreococcus tauri (a), Micromonas sp. RCC299 (b), Chlamydomonas reinhardtii (c) and Coccomyxa sp. C-169 (d), each peripheral bar representing a chromosome. The Bathycoccus BOC1 region genes (lower right corner, labeled as 'Bathy_BOC1') are connected by red lines to their orthologs (curated as best BLAST hits) on the chromosomes of other species. Where a Bathycoccus gene also represents a BOC1 Mamiellales core gene (Table 3), the link is colored blue. Green bars show the BOC1 regions in Bathycoccus, Micromonas and Ostreococcus. The Micromonas sp. RCC299 region showing partial clustering of BOC1 orthologs lacks typical BOC1 features. This region has high GC content (66%), is not enriched for a high intron content and does not group highly expressed genes (Table S4 in Additional file 1). For the sake of legibility, all small scaffolds of Chlamydomonas reinhardtii that harbored a Bathycoccus BOC1 orthologous gene were joined together into a virtual chromosome 00 (scaffolds 19, 20, 22, 23, 24, 26 and 32).