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.