Project description:The genome sequencing of Buchnera aphidicola BCc from the aphid Cinara cedri, which is the smallest known Buchnera genome, revealed that this bacterium had lost its symbiotic role, as it was not able to synthesize tryptophan and riboflavin. Moreover, the biosynthesis of tryptophan is shared with the endosymbiont Serratia symbiotica SCc, which coexists with B. aphidicola in this aphid. The whole-genome sequencing of S. symbiotica SCc reveals an endosymbiont in a stage of genome reduction that is closer to an obligate endosymbiont, such as B. aphidicola from Acyrthosiphon pisum, than to another S. symbiotica, which is a facultative endosymbiont in this aphid, and presents much less gene decay. The comparison between both S. symbiotica enables us to propose an evolutionary scenario of the transition from facultative to obligate endosymbiont. Metabolic inferences of B. aphidicola BCc and S. symbiotica SCc reveal that most of the functions carried out by B. aphidicola in A. pisum are now either conserved in B. aphidicola BCc or taken over by S. symbiotica. In addition, there are several cases of metabolic complementation giving functional stability to the whole consortium and evolutionary preservation of the actors involved.
Project description:We analysed the DNA methylation patterns of inguinal white adipose tissue in M-SCT floxed and M-SCT KO, the results indicated a significant widepread hypermethylation modification in M-SCT floxed which contributed to the increased obesity susceptibility of M-SCT floxed
Project description:Particularly interesting cases of mutualistic endosymbioses come from the establishment of co-obligate associations of more than one species of endosymbiotic bacteria. Throughout symbiotic accommodation from a free-living bacterium, passing through a facultative stage and ending as an obligate intracellular one, the symbiont experiences massive genomic losses and phenotypic adjustments. Here, we scrutinized the changes in the coevolution of Serratia symbiotica and Buchnera aphidicola endosymbionts in aphids, paying particular attention to the transformations undergone by S. symbiotica to become an obligate endosymbiont. Although it is already known that S. symbiotica is facultative in Acyrthosiphon pisum, in Cinara cedri it has established a co-obligate endosymbiotic consortium along with B. aphidicola to fulfill the aphid's nutritional requirements. The state of this association in C. tujafilina, an aphid belonging to the same subfamily (Lachninae) that C. cedri, remained unknown. Here, we report the genome of S. symbiotica strain SCt-VLC from the aphid C. tujafilina. While being phylogenetically and genomically very closely related to the facultative endosymbiont S. symbiotica from the aphid A. pisum, it shows a variety of metabolic, genetic, and architectural features, which point toward this endosymbiont being one step closer to an obligate intracellular one. We also describe in depth the process of genome rearrangements suffered by S. symbiotica and the role mobile elements play in gene inactivations. Finally, we postulate the supply to the host of the essential riboflavin (vitamin B2) as key to the establishment of S. symbiotica as a co-obligate endosymbiont in the aphids belonging to the subfamily Lachninane.
Project description:The pea aphid, Acyrthosiphon pisum, can host different facultative symbionts (FS), which may provide various benefits to the host, including adaptation to the host plant and resistance to heat or natural enemies (fungi, bacteria, parasitoid wasps). Here, we searched whether and how the presence of some FS could affect a key component of insect innate immunity, the phenoloxidase, under normal and stressed conditions. For this, we used A. pisum clones of different genetic background (LL01, YR2 and T3-8V1) and harboring or not FS (Regiella insecticola (Ri), Hamiltonella defensa (Hd) or Serratia symbiotica (Ss)). Proteomic analysis of aphid hemolymph and PCR indicated that the two A. pisum phenoloxidases, PO1 and PO2, are expressed and translated into protein. They seem mainly secreted as circulating enzymes in the hemolymph and a proteolytic cleavage was not necessary for their activation. PO genes expression was dependent upon the aphid genotypes as well as the amount of PO proteins and activity in the total hemolymph (T3-8V1-Amp > LL01 = YR2-Amp). The presence in YR2 and T3-8V1 clones of Hd or Ri, but not Ss, caused a sharp decrease in PO activity by interfering with both transcription and translation. Microinjection of different types of stressors (yeast, E. coli, latex beads) in YR2 lines affected the survival rate of aphids and in most cases, it also decreases the PO genes expression after 24h, whereas the amount and activity of the proteins varied differently depending on the FS and the stressor, regardless of the genes expression. These data provide new hypothesis on the mechanism by which some facultative symbionts act on the pea aphid immunity.
