There are two customizable steps in the OrthoFinder method: (1) the sequence search method and (2) the orthogroup tree inference method. The default option for step 1 is DIAMOND [5 (link)]. The default option for step 2 is DendroBLAST [24 (link)]. The default options are recommended by the authors as they are fast and achieve high accuracy on the Quest for Orthologs benchmarks [1 (link)] (Fig. 4 a–d). However, the user is free to substitute any alternative methods for these steps. Currently, supported methods for step 1 include BLAST [4 (link)] and MMseqs2 [6 (link)]. Similarly, any combination of multiple sequence alignment and tree inference method can be substituted in for step 2. For illustrative purposes, the default multiple sequence alignment method is MAFFT [35 (link)] and the default tree inference method is FastTree [25 (link)]; this combination is benchmarked above. It is impossible for the authors to test all possible combinations of multiple sequence alignment and tree inference methods, and the selected methods were chosen because of their speed and scalability characteristics [25 (link), 35 (link)]. OrthoFinder provides flexibility for the user to select their preferred method. More accurate multiple sequence alignment and tree inference methods should give more accurate ortholog inference, and many studies exist comparing the accuracy and runtime characteristics of the available methods [36 (link), 37 (link)]. A user-editable configuration file is provided in JSON format that allows new sequence search, multiple sequence alignment, and tree inference methods to be added to OrthoFinder. To facilitate the trialing of alternative multiple sequence alignment and tree inference methods, OrthoFinder provides the option to restart an existing analysis after the orthogroup inference stage. This skips the requirement to compute the all-vs-all sequence search and orthogroup inference and thus accelerates testing of different internal steps.
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