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Background <p>Genome size in Lepidoptera is generally constrained, and heterochromatin is typically limited to sex chromosomes. In some cases, the heterochromatin and genome size increased, but the mechanisms underlying extreme genome and heterochromatin expansion remain poorly understood. Here, we investigated the structural and repetitive DNA composition of <i>Acyclania tenebrosa</i> genome, a species with high heterochromatin content, to explore how repetitive elements shape genome architecture.</p> Results <p><i>Acyclania tenebrosa</i> retains the ancestral and modal diploid number for Lepidoptera (male 2n = 62) and lacks major chromosomal fusions. The species exhibits an extremely large genome for Lepidoptera (male 1&#xa0;C = 2.09 Gb), whose expansion has been driven by multiple repetitive elements that predominantly form large heterochromatic blocks. Moreover, reshuffling of major rDNA was observed. The abundance of the estimated repeats, including satellite DNAs (satDNAs) and transposable elements (TEs) comprise ~ 68% of the genome content, including an unprecedented amplification of satDNAs among Lepidoptera (14.3% of genome content), specially dominated by the AtenSat01 family, which forms multiple heterochromatin blocks. Independent local amplification of satDNAs in terminal and interstitial regions was revealed by FISH mapping. The TEs were also abundant accounting for ~ 54% of the genome, particularly LINEs and LTRs also contributed to genome enlargement, with landscape analyses indicating temporally distinct waves of amplification.</p> Conclusions <p><i>Acyclania tenebrosa</i> represents a striking example of gradual, repeat-mediated genome expansion, without evidence of whole-genome duplication. The integration of cytogenetic and genomic analyses demonstrates that massive repeat-associated heterochromatin accumulation resulted in unprecedent genome architectures in Lepidoptera, challenging the view of limited heterochromatin content in this order.</p>

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Repeat-associated heterochromatin expansion in Acyclania tenebrosa, a noctuid with one of the largest lepidopteran genomes

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  • 发表日期：

    2026年2月2日

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  • Ana Elisa Gasparotto,
  • Ana Beatriz SM Ferretti,
  • Rhavenna Thaís Alves-Gomes,
  • Fernanda AF Soares,
  • Artur Orsetti,
  • Wellington R. Clarindo,
  • Diogo C. Cabral-de-Mello

摘要

Background

Genome size in Lepidoptera is generally constrained, and heterochromatin is typically limited to sex chromosomes. In some cases, the heterochromatin and genome size increased, but the mechanisms underlying extreme genome and heterochromatin expansion remain poorly understood. Here, we investigated the structural and repetitive DNA composition of Acyclania tenebrosa genome, a species with high heterochromatin content, to explore how repetitive elements shape genome architecture.

Results

Acyclania tenebrosa retains the ancestral and modal diploid number for Lepidoptera (male 2n = 62) and lacks major chromosomal fusions. The species exhibits an extremely large genome for Lepidoptera (male 1 C = 2.09 Gb), whose expansion has been driven by multiple repetitive elements that predominantly form large heterochromatic blocks. Moreover, reshuffling of major rDNA was observed. The abundance of the estimated repeats, including satellite DNAs (satDNAs) and transposable elements (TEs) comprise ~ 68% of the genome content, including an unprecedented amplification of satDNAs among Lepidoptera (14.3% of genome content), specially dominated by the AtenSat01 family, which forms multiple heterochromatin blocks. Independent local amplification of satDNAs in terminal and interstitial regions was revealed by FISH mapping. The TEs were also abundant accounting for ~ 54% of the genome, particularly LINEs and LTRs also contributed to genome enlargement, with landscape analyses indicating temporally distinct waves of amplification.

Conclusions

Acyclania tenebrosa represents a striking example of gradual, repeat-mediated genome expansion, without evidence of whole-genome duplication. The integration of cytogenetic and genomic analyses demonstrates that massive repeat-associated heterochromatin accumulation resulted in unprecedent genome architectures in Lepidoptera, challenging the view of limited heterochromatin content in this order.