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Satellite DNAs are conserved and differentially transcribed among Gryllus cricket species.

ABSTRACT: Satellite DNA (satDNA) is an abundant class of non-coding repetitive DNA that is preferentially found as tandemly repeated arrays in gene-poor heterochromatin but is also present in gene-rich euchromatin. Here, we used DNA- and RNA-seq from Gryllus assimilis to address the content and transcriptional patterns of satDNAs. We also mapped RNA-seq libraries for other Gryllus species against the satDNAs found in G. assimilis and G. bimaculatus genomes to investigate their evolutionary conservation and transcriptional profiles in Gryllus. Through DNA-seq read clustering analysis using RepeatExplorer, dotplots analysis and fluorescence in situ hybridization mapping, we found that ?4% of the G. assimilis genome is represented by 11 well-defined A?+?T-rich satDNA families. These are mainly located in heterochromatic areas, with some repeats able to form high-order repeat structures. By in silico transcriptional analysis we identified satDNAs that are conserved in Gryllus but differentially transcribed. The data regarding satDNA presence in G. assimilis genome were discussed in an evolutionary context, with transcriptional data enabling comparisons between sexes and across tissues when possible. We discuss hypotheses for the conservation and transcription of satDNAs in Gryllus, which might result from their role in sexual differentiation at the chromatin level, heterochromatin formation and centromeric function.

SUBMITTER: Palacios-Gimenez OM

PROVIDER: S-EPMC5909420 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Satellite DNAs are conserved and differentially transcribed among Gryllus cricket species.

Palacios-Gimenez Octavio Manuel OM Bardella Vanessa Bellini VB Lemos Bernardo B Cabral-de-Mello Diogo Cavalcanti DC

DNA research : an international journal for rapid publication of reports on genes and genomes 20180401 2

Satellite DNA (satDNA) is an abundant class of non-coding repetitive DNA that is preferentially found as tandemly repeated arrays in gene-poor heterochromatin but is also present in gene-rich euchromatin. Here, we used DNA- and RNA-seq from Gryllus assimilis to address the content and transcriptional patterns of satDNAs. We also mapped RNA-seq libraries for other Gryllus species against the satDNAs found in G. assimilis and G. bimaculatus genomes to investigate their evolutionary conservation an ...[more]

PMID: 29096008

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Project description:BackgroundSatellite DNAs (satDNAs) are tandemly repeated non-coding DNA sequences that belong to the most abundant and the fastest evolving parts of the eukaryotic genome. A satellitome represents the collection of different satDNAs in a genome. Due to extreme diversity and methodological difficulties to characterize and compare satDNA collection in complex genomes, knowledge on their putative functional constraints and capacity to participate in genome evolution remains rather elusive. SatDNA transcripts have been detected in many species, however comparative studies of satDNA transcriptome between species are extremely rare.ResultsWe conducted a genome-wide survey and comparative analyses of satellitomes among different closely related Meloidogyne spp. nematodes. The evolutionary trends of satDNAs suggest that each round of proposed polyploidization in the evolutionary history is concomitant with the addition of a new set of satDNAs in the satellitome of any particular Meloidogyne species. Successive incorporation of new sets of satDNAs in the genome along the process of polyploidization supports multiple hybridization events as the main factor responsible for the formation of these species. Through comparative analyses of 83 distinct satDNAs, we found a CENP-B box-like sequence motif conserved among 11 divergent satDNAs (similarity ranges from 36 to 74%). We also found satDNAs that harbor a splice leader (SL) sequence which, in spite of overall divergence, shows conservation across species in two putative functional regions, the 25-nt SL exon and the Sm binding site. Intra- and interspecific comparative expression analyses of the complete satDNA set in the analyzed Meloidogyne species revealed transcription profiles including a subset of 14 actively transcribed satDNAs. Among those, 9 show active transcription in every species where they are found in the genome and throughout developmental stages.ConclusionsOur results demonstrate the feasibility and power of comparative analysis of the non-coding repetitive genome for elucidation of the origin of species with a complex history. Although satDNAs generally evolve extremely quickly, the comparative analyses of 83 satDNAs detected in the analyzed Meloidogyne species revealed conserved sequence features in some satDNAs suggesting sequence evolution under selective pressure. SatDNAs that are actively transcribed in related genomes and throughout nematode development support the view that their expression is not stochastic.

Project description:Neotropical fishes have highly diversified karyotypic and genomic characteristics and present many diverse sex chromosome systems, with various degrees of sex chromosome differentiation. Knowledge on their sex-specific composition and evolution, however, is still limited. Satellite DNAs (satDNAs) are tandemly repeated sequences with pervasive genomic distribution and distinctive evolutionary pathways, and investigating satDNA content might shed light into how genome architecture is organized in fishes and in their sex chromosomes. The present study investigated the satellitome of Megaleporinus elongatus, a freshwater fish with a proposed Z1Z1Z2Z2/Z1W1Z2W2 multiple sex chromosome system that encompasses a highly heterochromatic and differentiated W1 chromosome. The species satellitome comprises of 140 different satDNA families, including previously isolated sequences and new families found in this study. This diversity is remarkable considering the relatively low proportion that satDNAs generally account for the M. elongatus genome (around only 5%). Differences between the sexes in regards of satDNA content were also evidenced, as these sequences are 14% more abundant in the female genome. The occurrence of sex-biased signatures of satDNA evolution in the species is tightly linked to satellite enrichment associated with W1 in females. Although both sexes share practically all satDNAs, the overall massive amplification of only a few of them accompanied the W1 differentiation. We also investigated the expansion and diversification of the two most abundant satDNAs of M. elongatus, MelSat01-36 and MelSat02-26, both highly amplified sequences in W1 and, in MelSat02-26’s case, also harbored by Z2 and W2 chromosomes. We compared their occurrences in M. elongatus and the sister species M. macrocephalus (with a standard ZW sex chromosome system) and concluded that both satDNAs have led to the formation of highly amplified arrays in both species; however, they formed species-specific organization on female-restricted sex chromosomes. Our results show how satDNA composition is highly diversified in M. elongatus, in which their accumulation is significantly contributing to W1 differentiation and not satDNA diversity per se. Also, the evolutionary behavior of these repeats may be associated with genome plasticity and satDNA variability between the sexes and between closely related species, influencing how seemingly homeologous heteromorphic sex chromosomes undergo independent satDNA evolution.

Dataset Information

Satellite DNAs are conserved and differentially transcribed among Gryllus cricket species.

Publications

Satellite DNAs are conserved and differentially transcribed among Gryllus cricket species.

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