Structure of the aphid LdcA. (A) ClustalX alignment of amino acid sequences of LdcAs. Residues conserved in all lineages, four lineages, and three lineages are shaded black, dark gray, and light gray, respectively. Arrowheads indicate the residues required for LdcA activity. The long form of the aphid LdcA is used for the alignment. (B) Domain structure of the aphid LdcA protein and structures of the corresponding mRNA and genomic DNA.