Abstract
Forkhead box (Fox) genes code for transcription factors that play important roles in different biological processes. They are found in a wide variety of organisms and appeared in unicellular eukaryotes. In metazoans, the gene family includes many members that can be subdivided into 24 classes. Cephalochordates are key organisms to understand the functional evolution of gene families in the chordate lineage due to their phylogenetic position as an early divergent chordate, their simple anatomy and genome structure. In the genome of the cephalochordate amphioxus Branchiostoma floridae, 32 Fox genes were identified, with at least one member for each of the classes that were present in the ancestor of bilaterians. In this work we describe the expression pattern of 13 of these genes during the embryonic development of the Mediterranean amphioxus, Branchiostoma lanceolatum. We found that FoxK and FoxM genes present an ubiquitous expression while all the others show specific expression patterns restricted to diverse embryonic territories. Many of these expression patterns are conserved with vertebrates, suggesting that the main functions of Fox genes in chordates were present in their common ancestor.
Highlights
Forkhead box (Fox) transcription factors originated early during evolution and are specific to opisthokonts
Molecular Phylogenetic Analysis of B. lanceolatum Fox Gene Sequences We looked for Fox gene sequences in the reference transcriptome of B. lanceolatum (Oulion et al, 2012)
We showed that B. lanceolatum possesses at least 28 Fox genes, each of them being orthologous to one of the 32 genes described in B. floridae and corresponding to at least one member of each of the 22 families present in the bilaterian ancestor (Yu et al, 2008a)
Summary
Forkhead box (Fox) transcription factors originated early during evolution and are specific to opisthokonts. They are present in fungi as well as in metazoans (Mazet et al, 2006; Larroux et al, 2008; Shimeld et al, 2010a) in which they play essential roles during embryonic development (Carlsson and Mahlapuu, 2002; Tuteja and Kaestner, 2007a,b; Benayoun et al, 2011). It has been proposed that 22 Fox gene families were already present in the bilaterian ancestor (Shimeld et al, 2010b)
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