Concerning their role in olfaction, only two CCEs able to metabolize sex pheromones have been functionally characterized in insects.
It ranged between the kcat values of the two CCEs previously characterized as PDEs in A. polyphemus (Apol-PDE) and in P. japonica (Pjap-PDE): kcat values for the sex pheromone of 127 s−1 [18] and 1.36 s−1 (calculated from [17]), respectively.
However, only two CCEs were both identified at the molecular level and functionally characterized as PDEs until recently.
Two CCEs, enriched in antennae and belonging to distinct clades, were shown to present different substrate specificities toward pheromone and plant compounds.
We have then selected two CCEs restricted to the antennae to test their catalytic properties toward pheromones but also toward plant components.
Each species had at most one CCE in each neuroligin subcluster, while B. mori had two CCEs in the Nlg-4 subcluster, the first evidence of a neuroligin duplication event in the Insecta.
We have functionally characterized two CCEs, SlCXE10 and SlCXE7, belonging to the first and second class, respectively., In situ hybridization revealed that these two genes were associated with long and short olfactory sensilla, tuned to pheromones and plant odorants, respectively.
Investigation of detoxification genes specifically over-expressed in each resistant strain disclosed that two CCEs, one UGT, and 11 P450s (in total 14) were specifically up regulated in GR9-IS strain, with one CCE and one P450 having the higher logFC (2.7 and 3.7 respectively).
Seven CCE and six GST genes were also found among NWS unigenes.
The lack of complementation suggests that these five cce mutants are allelic and thus designated as cce5-1 to cce5-5.
