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Evolution of multipartite mitochondrial genomes in the booklice of the genus Liposcelis (Psocoptera).

Chen SC, Wei DD, Shao R, Shi JX, Dou W, Wang JJ - BMC Genomics (2014)

Bottom Line: We found that these two species of booklice also have multipartite mt genomes, like L. bostrychophila, with the mt genes we identified on two chromosomes.Numerous pseudo mt genes and non-coding regions were found in the mt genomes of these two booklice, and account for 30% and 10% respectively of the entire length we sequenced.L. entomophila and L. paeta differ substantially from each other and from L. bostrychophila in gene content and gene arrangement in their mt chromosomes.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, P, R, China. jjwang7008@yahoo.com.

ABSTRACT

Background: The genus Liposcelis (Psocoptera: Troctomorpha) has more than 120 species with a worldwide distribution and they pose a risk for global food security. The organization of mitochondrial (mt) genomes varies between the two species of booklice investigated in the genus Liposcelis. Liposcelis decolor has its mt genes on a single chromosome, like most other insects; L. bostrychophila, however, has a multipartite mt genome with genes on two chromosomes.

Results: To understand how multipartite mt genome organization evolved in the genus Liposcelis, we sequenced the mt genomes of L. entomophila and L. paeta in this study. We found that these two species of booklice also have multipartite mt genomes, like L. bostrychophila, with the mt genes we identified on two chromosomes. Numerous pseudo mt genes and non-coding regions were found in the mt genomes of these two booklice, and account for 30% and 10% respectively of the entire length we sequenced. In L. bostrychophila, the mt genes are distributed approximately equally between the two chromosomes. In L. entomophila and L. paeta, however, one mt chromosome has most of the genes we identified whereas the other chromosome has largely pseudogenes and non-coding regions. L. entomophila and L. paeta differ substantially from each other and from L. bostrychophila in gene content and gene arrangement in their mt chromosomes.

Conclusions: Our results indicate unusually fast evolution in mt genome organization in the booklice of the genus Liposcelis, and reveal different patterns of mt genome fragmentation among L. bostrychophila, L. entomophila and L. paeta.

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Alignment of nucleotide sequences of “cox2 + NCRI-1” from chromosome I and “Pcox2-2 + NCRII-2” inLiposcelis entomophila. Consensus sequences are shown in the green background.
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Fig7: Alignment of nucleotide sequences of “cox2 + NCRI-1” from chromosome I and “Pcox2-2 + NCRII-2” inLiposcelis entomophila. Consensus sequences are shown in the green background.

Mentions: Prior to the present study, pseudo mt genes have been described in L. bostrychophila and numerous other animals. Most of the pseudo mt genes are short and derived from tRNAs [40, 51–56]. Pseudo mt genes longer than 100 bp, derived from protein-coding genes, were also reported [13, 57–60]. Mt gene rearrangements are usually explained by a tandem duplication-random loss (TDRL) model [61, 62], and pseudo mt genes are considered to be redundant genes in the process of being eliminated [53, 54, 57]. The large numbers of pseudo mt genes we found in L. entomophila and L. paeta in this study and in L. bostrychophila[13] are extraordinary for insects and animals, indicating that large-scale changes, such as tandem duplication or mt chromosome duplication, occurred relatively recently in the multipartite mt genomes of these booklice. Intriguingly, no pseudo mt gene has been found in L. decolor, although it also has numerous gene rearrangements like the other three Liposcelis species that have multipartite mt genomes [15]. It infers that mt genome fragmenting is the important inducement for pseudo mt gene appearance in booklice. For fragmented mt genomes, mt pseudogenes were found in the human pubic louse [26], the Polyplax rat lice [40], the Globodera nematodes [59, 60] and the chimeric mt minichromosomes of the human body louse [63]. The explanation for the pseudo mt gene present in these species is that a recombinatorial mechanism is responsible for their production. This explanation may be applicable for multipartite mt genome in Liposcelis, pseudo mt gene would be residues of interchromosome recombination. Duplicated non-coding sequence present coincided with pseudo mt gene in booklice multipartite mt genomes. The sequences, “cox2 + NCRI-1” from chromosome I and “Pcox2-2 + NCRII-2” from chromosome II in L. entomophila, have a 98.95% similarity and four nucleotides changed (Figure 7). This indicats that “Pcox2-2 + NCRII-2” is generated as an entire block and derived from “cox2 + NCRI-1”. Therefore, the causation of duplicated non-coding sequences present in booklice might be consistent with that of pseudo mt genes. The same situation has also been found in L. bostrychophila[13] and human body louse [63].Figure 7


Evolution of multipartite mitochondrial genomes in the booklice of the genus Liposcelis (Psocoptera).

Chen SC, Wei DD, Shao R, Shi JX, Dou W, Wang JJ - BMC Genomics (2014)

Alignment of nucleotide sequences of “cox2 + NCRI-1” from chromosome I and “Pcox2-2 + NCRII-2” inLiposcelis entomophila. Consensus sequences are shown in the green background.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4197233&req=5

Fig7: Alignment of nucleotide sequences of “cox2 + NCRI-1” from chromosome I and “Pcox2-2 + NCRII-2” inLiposcelis entomophila. Consensus sequences are shown in the green background.
Mentions: Prior to the present study, pseudo mt genes have been described in L. bostrychophila and numerous other animals. Most of the pseudo mt genes are short and derived from tRNAs [40, 51–56]. Pseudo mt genes longer than 100 bp, derived from protein-coding genes, were also reported [13, 57–60]. Mt gene rearrangements are usually explained by a tandem duplication-random loss (TDRL) model [61, 62], and pseudo mt genes are considered to be redundant genes in the process of being eliminated [53, 54, 57]. The large numbers of pseudo mt genes we found in L. entomophila and L. paeta in this study and in L. bostrychophila[13] are extraordinary for insects and animals, indicating that large-scale changes, such as tandem duplication or mt chromosome duplication, occurred relatively recently in the multipartite mt genomes of these booklice. Intriguingly, no pseudo mt gene has been found in L. decolor, although it also has numerous gene rearrangements like the other three Liposcelis species that have multipartite mt genomes [15]. It infers that mt genome fragmenting is the important inducement for pseudo mt gene appearance in booklice. For fragmented mt genomes, mt pseudogenes were found in the human pubic louse [26], the Polyplax rat lice [40], the Globodera nematodes [59, 60] and the chimeric mt minichromosomes of the human body louse [63]. The explanation for the pseudo mt gene present in these species is that a recombinatorial mechanism is responsible for their production. This explanation may be applicable for multipartite mt genome in Liposcelis, pseudo mt gene would be residues of interchromosome recombination. Duplicated non-coding sequence present coincided with pseudo mt gene in booklice multipartite mt genomes. The sequences, “cox2 + NCRI-1” from chromosome I and “Pcox2-2 + NCRII-2” from chromosome II in L. entomophila, have a 98.95% similarity and four nucleotides changed (Figure 7). This indicats that “Pcox2-2 + NCRII-2” is generated as an entire block and derived from “cox2 + NCRI-1”. Therefore, the causation of duplicated non-coding sequences present in booklice might be consistent with that of pseudo mt genes. The same situation has also been found in L. bostrychophila[13] and human body louse [63].Figure 7

Bottom Line: We found that these two species of booklice also have multipartite mt genomes, like L. bostrychophila, with the mt genes we identified on two chromosomes.Numerous pseudo mt genes and non-coding regions were found in the mt genomes of these two booklice, and account for 30% and 10% respectively of the entire length we sequenced.L. entomophila and L. paeta differ substantially from each other and from L. bostrychophila in gene content and gene arrangement in their mt chromosomes.

View Article: PubMed Central - PubMed

Affiliation: Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, P, R, China. jjwang7008@yahoo.com.

ABSTRACT

Background: The genus Liposcelis (Psocoptera: Troctomorpha) has more than 120 species with a worldwide distribution and they pose a risk for global food security. The organization of mitochondrial (mt) genomes varies between the two species of booklice investigated in the genus Liposcelis. Liposcelis decolor has its mt genes on a single chromosome, like most other insects; L. bostrychophila, however, has a multipartite mt genome with genes on two chromosomes.

Results: To understand how multipartite mt genome organization evolved in the genus Liposcelis, we sequenced the mt genomes of L. entomophila and L. paeta in this study. We found that these two species of booklice also have multipartite mt genomes, like L. bostrychophila, with the mt genes we identified on two chromosomes. Numerous pseudo mt genes and non-coding regions were found in the mt genomes of these two booklice, and account for 30% and 10% respectively of the entire length we sequenced. In L. bostrychophila, the mt genes are distributed approximately equally between the two chromosomes. In L. entomophila and L. paeta, however, one mt chromosome has most of the genes we identified whereas the other chromosome has largely pseudogenes and non-coding regions. L. entomophila and L. paeta differ substantially from each other and from L. bostrychophila in gene content and gene arrangement in their mt chromosomes.

Conclusions: Our results indicate unusually fast evolution in mt genome organization in the booklice of the genus Liposcelis, and reveal different patterns of mt genome fragmentation among L. bostrychophila, L. entomophila and L. paeta.

Show MeSH
Related in: MedlinePlus