Contrasting Sex-and Caste-Dependent piRNA Profiles in the Transposon Depleted Haplodiploid Honeybee Apis mellifera

Date

2017

Authors

Wang, Wei
Ashby, Regan
Ying, Hua
Maleszka, Ryszard
Foret, Sylvain

Journal Title

Journal ISSN

Volume Title

Publisher

Oxford University Press

Abstract

Protecting genome integrity against transposable elements is achieved by intricate molecular mechanisms involving PIWI proteins, their associated small RNAs (piRNAs), and epigenetic modifiers such as DNA methylation. Eusocial bees, in particular the Western honeybee, Apis mellifera, have one of the lowest contents of transposable elements in the animal kingdom, and, unlike other animals with a functional DNA methylation system, appear not to methylate their transposons. This raises the question of whether the PIWI machinery has been retained in this species. Using comparative genomics, mass spectrometry, and expressional profiling, we present seminal evidence that the piRNA system is conserved in honeybees. We show that honey bee piRNAs contain a 2'-O-methyl modification at the 3' end, and have a bias towards a 5' terminal U, which are signature features of their biogenesis. Both piRNA repertoire and expression levels are greater in reproductive individuals than in sterile workers. Haploid males, where the detrimental effects of transposons are dominant, have the greatest piRNA levels, but surprisingly, the highest expression of transposons. These results show that even in a transposon-depleted species, the piRNA system is required to guard the vulnerable haploid genome and reproductive castes against transposon-associated genomic instability. This also suggests that dosage plays an important role in the regulation of transposons and piRNAs expression in haplo-diploid systems.

Description

Keywords

piRNA,, PIWI proteins, transposons, honeybee, haplodiploid, mass spectrometry

Citation

Source

Genome Biology and Evolution

Type

Journal article

Book Title

Entity type

Access Statement

Open Access

License Rights

Creative Commons Attribution licence

DOI

10.1093/gbe/evx087

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