Screenshot of the 'Orthology' tool. For any gene in the database, FLAGdb++ displays information about the closest homologous genes in the four integrated species in order to assist the prediction of orthology relationships. The results of all the reciprocal best BLASTP hits (RBH) are displayed together graphically, along with the global protein alignment and intron-exon structures of the genes concerned. In this way, gene structure can also be considered in the prediction of orthologs and eventual erroneous structural annotation (such as gene merging), which render the RBH approach futile, can be easily detected and removed. In this example, all the BLASTP best hits are reciprocal between all genome species (green lines) except between Vitis and Populus genomes.