In insects, several examples suggest the involvement of Pglycoproteins in the resistance to insecticides used for crop protection. However, only few P-glycoprotein-like genes have been linked to a xenobiotic substrate such as Mdr49 and Mdr65 of D. melanogaster with tolerance against colchicine and a-amanitin, respectively. Mdr49 can act also as transporter for a germ cell attractant in fruit flies. Recent studies on lepidopteran species revealed that a P-glycoprotein-like transporter mediates the efflux of cardenolides in the nerve cord and thereby prevents the interactions of these toxins Baicalin with the susceptible target site of Na+/K+-ATPases. Similar to other insects, the eight sequences from C. populi encode full and half transporters. Bootstrapping of the ABCB phylogenetic tree in Figure 3 and Figure S1 produced nodes weakly supporting segregation of this subfamily containing human and insect ABCB sequences. Based on our phylogenetic analysis,Euphorbia factor L3 we found no homologs to TAP sequences in the insects, but insect homologs to the other human peptide transporters were identified. In accordance with the literature, we can also speculate that TAPL is the ancestor of the TAP family. Members of the ABCD subfamily are involved in the translocation of fatty acids into peroxisomes. The ABC transporters are half-size and assemble mostly as a homodimer after posttranslational transport to peroxisomal membranes. ABCD4 is not a peroxisomal membrane protein but an ERresident protein that mediates translocation of lipid molecules essential for lipid metabolism in the ER. Unlike humans but like all other sequenced insects C. populi contains two ABCD half transporters. Because they are homologous to the human peroxisomal and T. castaneum transporters, a similar function can be inferred in poplar leaf beetles. No insect sequence could be grouped to ABCD4. The ABCE and ABCF proteins comprise a pair of linked NBDs but lack TMDs. Therefore, they are not involved in molecule transport, but they are active in a wide range of other functions pivotal for cell viability. For example, the human ABCE1 not only acts as a ribonuclease L inhibitor, it also regulates RNA stability, viral infection, tumor cell proliferation, anti-apoptosis, translation initiation, elongation, termination, and ribosome recycling.