Long terminal repeat (LTR) retrotransposons are mobile DNA sequences that ubiquitously exist in eukaryotic genomes. They replicate themselves in the genome by copy-paste mechanism with RNA as medium. In higher plants, many active LTR retrotransposons have been applied to analyze molecular marker technology, genetic tagging, insertion mutation and gene function. Here, we systematically review the characteristics of plant active LTR retrotransposons, including their structures, copy numbers and distributions. We further analyzed the gag (group-specific antigen) and pol (polymerase) sequence features of different plants active LTR retrotransposons and the distribution patterns of the cis-acting elements in LTR regions. The results show that autonomous active LTR retrotransposons must contain LTR regions and code Gag, Pr, Int, Rt, Rh proteins. Both LTR regions are highly homologous with each other and contain many cis-regulatory elements; RVT and RNase_H1_RT domain are essential for Rt and Rh protein respectively. These results provide the basis for subsequent identification of plant active LTR retrotransposons and their functional analysis.
Genome, Plant ; Mutagenesis, Insertional ; Plants ; genetics ; Retroelements ; Terminal Repeat Sequences

Transposable elements (TEs), particularly, long terminal repeat retrotransposons (LTR-RTs), are the most abundant DNA components in all plant species that have been investigated, and are largely responsible for plant genome size variation. Although plant genomes have experienced periodic proliferation and/or recent burst of LTR-retrotransposons, the majority of LTR-RTs are inactivated by DNA methylation and small RNA-mediated silencing mechanisms, and/or were deleted/truncated by unequal homologous recombination and illegitimate recombination, as suppression mechanisms that counteract genome expansion caused by LTR-RT amplification. LTR-RT DNA is generally enriched in pericentromeric regions of the host genomes, which appears to be the outcomes of preferential insertions of LTR-RTs in these regions and low effectiveness of selection that purges LTR-RT DNA from these regions relative to chromosomal arms. Potential functions of various TEs in their host genomes remain blurry; nevertheless, LTR-RTs have been recognized to play important roles in maintaining chromatin structures and centromere functions and regulation of gene expressions in their host genomes.
Evolution, Molecular ; Gene Silencing ; Genome, Plant ; genetics ; Plants ; genetics ; Retroelements ; genetics ; Terminal Repeat Sequences ; genetics

Estrogen receptor (esr) mediates the effects of estrogen on the expression of related genes, thereby regulating the growth and reproduction of mammals. To investigate the effect of retrotransposon insertion polymorphism (RIP) of the porcine esr gene on porcine growth performance, retrotransposon insertion polymorphism of the esr gene were predicted by comparative genomics and bioinformatics, and PCR was used to verify the insertion polymorphisms in different porcine breeds. Finally, the correlation analysis between the genotypes and performance of Large White pigs was conducted. The results showed that four retrotransposon polymorphic sites were identified in the esr1 and esr2 genes, which are esr1-SINE- RIP1 located in intron 2 of the esr1 gene, esr1-LINE-RIP2 and RIP3-esr1- SINE located in intron 5 of the gene, and esr2-LINE-RIP located in intron 1 of the esr2 gene, respectively. Among them, insertion of a 287 bp of SINE into intron 2 of the esr1 gene significantly affected (P<0.05) the live back fat thickness and 100 kg body weight back fat thickness of Large White pigs. Moreover, the live back fat thickness and back fat thickness at 100 kg body weight of homozygous with insertion (SINE+/+) was significantly greater than that of heterozygous with insertion (SINE+/-) and homozygous without insertion (SINE-/-). Therefore, esr1-SINE-RIP1 could be used as a molecular marker to assist the selection of deposition traits in Large White pigs.
Animals ; Genotype ; Introns/genetics* ; Phenotype ; Polymorphism, Genetic/genetics* ; Retroelements/genetics* ; Swine/genetics*

The dynamic activity of transposable elements (TEs) contributes to the vast diversity of genome size and architecture among plants. Here, we examined the genomic distribution and transposition activity of long terminal repeat retrotransposons (LTR-RTs) in Arabidopsis thaliana (Ath) and three of its relatives, Arabidopsis lyrata (Aly), Eutrema salsugineum (Esa), and Schrenkiella parvula (Spa), in Brassicaceae. Our analyses revealed the distinct evolutionary dynamics of Gypsyretrotransposons, which reflects the different patterns of genome size changes of the four species over the past million years. The rate of Gypsy transposition in Aly is approximately five times more rapid than that of Ath and Esa, suggesting an expanding Aly genome. Gypsy insertions in Esa are strictly confined to pericentromeric heterochromatin and associated with dramatic centromere expansion. In contrast, Gypsy insertions in Spa have been largely suppressed over the last million years, likely as a result of a combination of an inherent molecular mechanism of preferential DNA removal and purifying selection at Gypsy elements. Additionally, species-specific clades of Gypsy elements shaped the distinct genome architectures of Aly and Esa.
Brassicaceae/genetics* ; Evolution, Molecular ; Genome Size ; Genome, Plant ; Genomics ; Phylogeny ; Retroelements ; Species Specificity

OBJECTIVETo investigate the susceptibility gene of type 2 diabetes mellitus (T2DM) through a novel strategy.

METHODSFirstly, the common feature of the putative susceptibility genes in the reported susceptibility loci was searched by using NCBI BLAST, and a functional L1 retrotransposon in the loci was found. Secondly, the mRNA expression level of the functional L1 retrotransposon in 25 Han T2DM patients and 22 normal controls was investigated by reverse transcription-polymerase chain reaction, and statistical analysis was implemented in statistical package SPSS10.0. Thirdly, L1 retrotransponson genome mutation screening was performed via sequencing.

RESULTSScreening the human genome for the retrotransposon genome via alignment with the L1 genome using NCBI BLAST showed the functional L1 retrotransposons distribute on most chromosomes except for chromosomes 19, 21 and Y on which rare type 2 diabetes susceptibility loci were reported to reside, and their distribution sites are consistent with the locations of the reported candidate type 2 diabetes susceptibility loci. The mRNA expression level of the functional L1 retrotransposon in the T2DM patients was significantly lower than that in normal subjects (P<0.001). Nonsense mutations including deletion and/or point mutations were observed in all of the 6 T2DM patients tested, but no mutation was observed in all of the 4 normal controls tested.

CONCLUSIONThe functional L1 retrotransposon may be a candidate susceptibility gene of type 2 diabetes or a key regulator of the susceptibility genes, and it may be an ideal candidate biomarker for screening type 2 diabetes.

Adult ; Chromosomes, Human ; genetics ; Databases, Genetic ; Diabetes Mellitus, Type 2 ; genetics ; Genetic Predisposition to Disease ; genetics ; Genome, Human ; genetics ; Genotype ; Humans ; Polymerase Chain Reaction ; Retroelements ; genetics

Using universal primer Ty1-copia retrotransposon RT,43 Ty1-copia like retrotransposon RT with high heterogeneity, stop codon mutation and frameshift mutation were amplified by PCR from genomic DNA of Zhejiang Lin'an (C15) and Yunnan Guangnan (A39) of Dendrobium officinale. The length of these sequences varied from 260 to 266 bp, and was rich in AT and consistency ranged from 47.1% to 97.7%. Different c/s-acting regulatory elements induced by low temperature, heat, light, all kinds of plant growth regulating substances and the starting transcription signals, corresponding to CAAT box, TATA box conserved sequences and some other regulatory elements. When being translated into amino acids, ten sequences presented stop codon mutation, five sequences presented frameshift mutation, and thirty-seven sequences presented conserved sequence "SLYGKQ" mutation. Six categories were identified through phylogenic analysis after alignment analyses of their amino acid sequences, and with other plants (eg. Triticum aestivum, Eleocharis quinqueflora) having high homology, which indicated that horizontal transmission of retrotransposon occurred among the plants in the past.
Amino Acid Sequence ; Cloning, Molecular ; Conserved Sequence ; DNA, Plant ; genetics ; Dendrobium ; enzymology ; genetics ; Molecular Sequence Data ; Phylogeny ; RNA-Directed DNA Polymerase ; chemistry ; genetics ; Retroelements ; genetics ; TATA Box ; genetics

Using universal primer Tyl-copia retrotransposon RT, the conserved reverse transcriptase domain of about 260 bp was amplified by RT-PCR from the Dendrobium officinale which induced by 100 micromol x L(-1) abscisic acid (ABA), indicating these retrotransposons activated by 100 micromol x L(-1) ABA. The amplicons were recovered and cloned,then sequenced and analyzed by related bioinformatics software. Forty-two Ty1-copia like retrotransposon RT transcriptionally activated were obtained with high heterogeneity. The length of these sequences varied from 247 to 266 bp, and was rich in AT and homology ranged from 46.3% to 98.9%. The same to Ty1-copia like retrotransposon RT of genome, different c/s-acting regulatory elements induced by stress conditions and the starting transcription signals, corresponding to CAAT box, TATA box conserved sequences and some other regulatory elements. The c/s-acting regulatory elements induced by stress conditions of reverse transcriptase transcriptionally activated of Tyl-copia retrotransposons were significantly increased than that of Ty1-copia like retrotransposon RT of genome. When being translated into amino acids, fifteen sequences presented stop codon mutation, nineteen sequences presented frameshift mutation, and all sequences presented conserved sequence "SLYGKQ" mutation. Five categories were identified through phylogenic analysis after alignment analyses of their amino acid sequences, and with Ty1-copia like retrotransposon RT of genome having low homology, which indicated that reverse transcriptase transcriptionally activated of Ty1-copia retrotransposons which induced by ABA had Significantly differences with Ty1-copia like retrotransposon RT of genome.
Abscisic Acid ; pharmacology ; Amino Acid Sequence ; Dendrobium ; drug effects ; genetics ; Molecular Sequence Data ; Phylogeny ; Retroelements ; drug effects ; Sequence Homology, Amino Acid ; Transcription, Genetic ; drug effects

To gain information on retrotransposons in the genome of Paragonimus westermani, PCR was carried out with degenerate primers, specific to protease and reverse transcriptase (rt) genes of long-terminal-repeat (LTR) retrotransposons. The PCR products were cloned and sequenced, after which 12 different retrotransposon-related sequences were isolated from the trematode genome. These showed various degrees of identity to the polyprotein of divergent retrotransposon families. A phylogenetic analysis demonstrated that these sequences could be classified into three different families of LTR retrotransposons, namely, Xena, Bel, and Gypsy families. Of these, two mRNA transcripts were detected by reverse transcriptase-PCR, showing that these two elements preserved their mobile activities. The genomic distributions of these two sequences were found to be highly repetitive. These results suggest that there are diverse retrotransposons including the ancient Xena family in the genome of P. westermani, which may have been involved in the evolution of the host genome.
Amino Acid Sequence ; Animals ; Cloning, Molecular ; DNA, Helminth/analysis ; *Evolution, Molecular ; *Genome ; Molecular Sequence Data ; Paragonimus/*genetics ; Phylogeny ; RNA-Directed DNA Polymerase/chemistry/genetics ; Retroelements/*genetics ; Sequence Alignment ; Sequence Analysis, DNA ; Terminal Repeat Sequences/*genetics

The evolutionary course of the CsRn1 long-terminal-repeat (LTR) retrotransposon was predicted by conducting a phylogenetic analysis with its paralog LTR sequences. Based on the clustering patterns in the phylogenetic tree, multiple CsRn1 copies could be grouped into four subsets, which were shown to have different integration times. Their differential sequence divergences and heterogeneous integration patterns strongly suggested that these subsets appeared sequentially in the genome of C. sinensis. Members of recently expanding subset showed the lowest level of divergence in their LTR and reverse transcriptase gene sequences. They were also shown to be highly polymorphic among individual genomes of the trematode. The CsRn1 element exhibited a preference for repetitive, agenic chromosomal regions in terms of selecting integration targets. Our results suggested that CsRn1 might induce a considerable degree of intergenomic variation and, thereby, have influenced the evolution of the C. sinensis genome.
Animals ; Clonorchis sinensis/*genetics ; DNA, Helminth/analysis/genetics ; *Evolution, Molecular ; Gene Dosage ; *Genome ; Phylogeny ; Polymorphism, Genetic ; RNA-Directed DNA Polymerase ; Retroelements/*genetics ; Sequence Analysis, DNA ; Terminal Repeat Sequences/*genetics

We exploited the serial analysis of gene expression (SAGE) libraries and human genome database in silico to correlate the breadth of expression (BOE; housekeep-ing versus tissue-specific genes) and peak rate of expression (PRE; high versus low expressed genes) with the density distribution of the retroelements. The BOE status is linearly associated with the density of the sense Alus along the 100 kb nucleotides region upstream of a gene, whereas the PRE status is inversely correlated with the density of antisense L1s within a gene and in the up- and downstream regions of the 0-10 kb nucleotides. The radial distance of intranuclear position, which is known to serve as the global domain for transcription regulation, is reciprocally correlated with the fractions of Alu (toward the nuclear center) and L1 (toward the nuclear edge) elements in each chromosome. We propose that the BOE and PRE statuses are related to the reciprocal distribution of Alu and L1 elements that formulate local and global expression domains.
Alu Elements/*genetics ; Chromosome Mapping/*methods ; Comparative Study ; Databases, Genetic ; Gene Expression Profiling/*methods ; Gene Expression Regulation/*genetics ; Genome, Human ; Humans ; Long Interspersed Nucleotide Elements/*genetics ; Retroelements/genetics ; Sequence Analysis, DNA/*methods ; Statistics ; Tissue Distribution