Syntenies of Nox/Duox genes. (A) Summary of the occurrence of Nox/Duox genes within eukaryotes. The number indicates the orthologs in each organism. Superscripted letters "a" and "b" represent incomplete amino acid sequences predicted from nucleotide fragments: a, 221 amino acid length of T. nigroviridis Nox4 and b, 201 amino acids of D. rerio Nox4 (sequences are shown in SD1). Superscripted letters "c" and "d" indicate these Nox5 orthologs do not contain N-terminal EF-hand-containing domain (#45 and #47 in Figure 2; sequences are shown in Additional file 4). A parenthesis represents an ambiguous classification of the "Ag-NoxM" (#38 in Figure 2) in the NoxA/NoxB subgroup. (B-G) Syntenies of the indicated vertebrate Noxes are shown. Genes are aligned in columns to illustrate orthology. Chromosome (Chr) or scaffold (Sc) numbers are indicated on the right.