Transcriptomic analysis of fat body from quasi-aposymbiotic Blattella germanica
We have explored the metabolic integration between Blattella  germanica and its obligate endosymbiont Blattabacterium cuenoti by comparative  transcriptomic analysis of the fat body of quasi-aposymbiotic cockroaches, where the  endosymbionts were almost removed by rifampicin treatment. Fat body from  quasi-aposymbiotic insects displayed large differences in gene expression  comparing/compared to the control population. Thus, in quasi-aposymbionts, the metabolism of  phenylalanine and tyrosine involved in cuticle sclerotization and melanization was  drastically increased to compensate the deficiency in the biosynthesis of these  amino acids by the endosymbionts. On the other hand, probably because the small  population of endosymbionts was unable to metabolize urea to ammonia, the  uricolytic pathway as well as the biosynthesis of uric acid were drastically  decreased. Immune system and antimicrobial peptides (AMPs) gene expression were also  altered in quasi-aposymbionts: two genes encoding peptidoglycan-recognition proteins  (one of them, a cytoplasmic isoform of PGRP-LB with amidase activity) were  underexpressed providing clues for the maintenance of the symbiotic relationship;  and three antimicrobial peptide genes were also underexpressed but their  involvement in the symbiotic relationship will require additional analysis, since their  main place of expression is hemolymph. Finally, searching for AMP-like factors,  two orphan genes encoding proteins smaller than 200 amino acids, whose expression  was mainly restricted to fat bodies were also underexpressed suggesting a link  with host-endosymbionts relationship.