Buchnera and aphids relationship test

buchnera and aphids relationship test

At that time, an ancestor of Buchnera infected an aphid ancestor. An important aspect in the evolution of this symbiosis is the vertical transmission of the. The relationship between aphids (Hemiptera: Aphididae) and the .. 6; Kruskal- Wallis test, P aphids reflects the high level of Buchnera. The pea aphid and its Buchnera symbiont are the animal symbiosis for .. s test ( Z test) (40), and multiple comparisons were conducted with a.

Genomic revelations of a mutualism: the pea aphid and its obligate bacterial symbiont

The generated amino acid sequences were used, in turn, as a template to align the corresponding nucleotides with MUSCLE v3. For each one of the genes present in B. Specifically, we applied a Tajima's relative rate test [ 25 ] with MEGA4, generating six comparisons for each of the aligned genes. Genes showing accelerated rates were grouped according to a nonredundant categories classification based on that used in the sequencing work on Aquifex aeolicus [ 26 ], with some modifications [ 27 ].

buchnera and aphids relationship test

Estimate of Evolutionary Acceleration among Genomes The sequence from the protein-coding genes shared by the four B. Three different estimates of substitution rates per site between species i and j Kij were carried out with MEGA4, using a the total and b nonsynonymous nucleotide positions, under the Kimura 2-parameters and the modified Nei-Gojobori methods, respectively, and c amino acid sequences, using the JTT substitution matrix. K01 and K02 were calculated according to Moran [ 28 ], being taxon 0 the last common ancestor of the endosymbiont strains compared in each test taxa 1 and 2.

The calculation of total and nonsynonymous substitutions allowed us to account for the phenomenon of saturation. This method has been successfully used previously to estimate saturation due to divergence [ 30 — 33 ]. Additionally, for each protein-coding gene under study, the values of both synonymous dS and nonsynonymous dN nucleotide substitutions were calculated, using a modified Nei-Gojobori model Jukes Cantor implemented by MEGA4 [ 23 ].

The T values used in these analyses were MY for B. These are the previously determined lowest values for each range of estimated divergence times among strains [ 15 ], based on the range of 50 to 70 MY since the strains used for calibration B. Phylogenetic Analyses Since saturation was achieved at the third position in all comparisons but BAp and BSg, in order to reduce the loss of phylogenetic signal we excluded this position when working with nucleotides to perform our phylogenetic analyses.

The concatenated sequence of the protein-coding genes shared by the four B. Nucleotides and amino acids were also used for Bayesian analysis, with MrBayes v3.

Buchnera - Aphids

In a previous study, the evolutionary analyses of the four B. Statistical Analyses All statistical analyses were performed using the software package R http: However, if an antibiotic that kills bacteria is added to the medium, the aphids fail to grow and reproduce.

This suggests that bacterial symbionts are essential in supplying the amino acids. This was further supported using labelled sulfur or nitrogen compounds that showed amino acids containing these labels appearing in the symbionts and being provided to the host.

Aphids and Buchnera

The symbionts genome also reflects this biosynthetic activity. Buchnera aphidicola, the symbiont of Schizaphis graminum, carries on a plasmid the two genes trpEG which are important in tryptophan synthesis. Each bacterium contains three or four plasmids that contain four tandem repeats of these genes, resulting in 12 to 16 copies of trpEG.

The Host Supplies Symbiont Nutrients The intracellular location of the symbionts requires that the host supplies the bacteria with energy, carbon, and nitrogen. One amino acid, gluatmine, is very abundant in the phloem. It was shown that glutamine is ingested by the aphid and transported to the cells in which the symbionts are housed bacteriocytes. The bacteriocytes take up glutamine, convert it to glutamic acid, that in turn is taken up by the bacterial symbiont.

buchnera and aphids relationship test

The nitrogen from glutamic acid is then used to synthesize the other amino acids which are ultimately utilized by the host animal. This cycling of amino acids permits the growth and reproduction of aphids.

Location of the symbionts The symbionts are found inside host cells intracellular that are called bacteriocytes also called mycetocytes. Each symbiont is surrounded by a membrane derived from the host cell that forms a vesicle called the symbiosome. The amino acids produced by the bacterial symbiont are thought to be released and taken up by the host cells.

John Werren, Tuesday, February 10, 2015

Digestion or destruction of the symbionts does not usually occur except during specific developmental stages. Being intracellular symbionts, the bacteria rely on the host to ensure transmission to the next generation.

In several aspects, these intracellular bacteria resemble cellular organelles. The study of this system, as well as other symbioses with intracellular symbionts, may aid in understanding how mitochondria and plastids became an integral part of eukaryotic cells. Genome sequence of the symbiont The sequence of the symbiont's genome was determined. These bacteria-housing cells have been discovered in insects of various orders and are all crucial for host fitness.

In aphids, bacteriocytes together form the bacteriome, which are structures located near to the midgut of their host.

buchnera and aphids relationship test

Buchnera are maternally passed to insect offsprings during reproduction through the ovary and eggs [6] to ensure continuous transmission. Nutrients in the environment Buchnera are continuously provided with nutrients from the host, most of them including carbohydrates and nonessential amino acids glutamate, serine, aspartate, glutamine, proline, alanine and asparagine that are synthesized by the host or found abundant in plant saps.

Such unique environment resulted in high dependence of Buchnera on their host and is reflected in the small size and composition of its genome [5]. Genome studies have shown that many of the crucial metabolic genes seen in free-living bacteria are not found in Buchnera genomes. Host gene regulation determines environmental conditions Unlike other environments, physical and chemical conditions within an organism could be largely determined by genetic backgrounds of the hosts.

Studies in expression profiles of aphids have shown that genes involving non-essential and essential amino acid biosynthesis are up-regulated in bacteriocytes harboring Buchnera, which provide nutrients or partial biosynthetic steps of essential amino acids [7].

buchnera and aphids relationship test

Microbial communities Buchnera aphidicola Cells of Buchnera are round or oval-shaped and lack flagella. Analysis of 16s rRNAs from Buchnera have shown that they belong to the gamma-3 subgroup of Proteobacteria, and are related with the Enterobacteriaceae family [3].

They have extremely small genomes and lack genes for many extracellular structures or metabolic pathways found in other closely related bacteria [6].

Genomic revelations of a mutualism: the pea aphid and its obligate bacterial symbiont

Other symbionts in aphids Besides Buchnera, other bacteria have also been found in aphids either living within bacteriocytes or not [8]. Among them include Wolbachia species and Hamiltonella defensa. The latter has be found to benefit their host by providing them protection against natural enemies [9].

Microbial processes and activities Biosynthesis of essential amino acids Treatments of antibiotics on aphids have shown detrimental effects in development and reproduction, which could be complemented by supplementation of crucial amino acids in diets.

buchnera and aphids relationship test

Together with findings showing retention of amino acids biosynthesis genes in the small Buchnera genome, it was concluded that Buchnera benefit their host mainly by producing essential amino acids [5] [2]. Utilization of nutrients in the host Due to the genome reduction process during evolution, Buchnera have lost genes necessary to produce many nutrients [5].