(Oxford University Press, 2017) Borgognone, Alessandra; Castanera Andrés, Raúl; Muguerza Domínguez, Elaia; Pisabarro de Lucas, Gerardo; Ramírez Nasto, Lucía; Producción Agraria; Nekazaritza Ekoizpena; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Helitrons constitute a superfamily of DNA transposons that were discovered in silico and are
widespread in most eukaryotic genomes. They are postulated to mobilize through a “rollingcircle”
mechanism, but the experimental evidence of their transposition has been described
only recently. Here, we present the inheritance patterns of HELPO1 and HELPO2 helitron families
in meiotically derived progeny of the basidiomycete Pleurotus ostreatus. We found distorted
segregation patterns of HELPO2 helitrons that led to a strong under-representation of
these elements in the progeny. Further investigation of HELPO2 flanking sites showed that
gene conversion may contribute to the elimination of such repetitive elements in meiosis, favouring
the presence of HELPO2 vacant loci. In addition, the analysis of HELPO2 content in a reconstructed
pedigree of subclones maintained under different culture conditions revealed an
event of helitron somatic transposition. Additional analyses of genome and transcriptome data
indicated that P. ostreatus carries active RNAi machinery that could be involved in the control
of transposable element proliferation. Our results provide the first evidence of helitron mobilization
in the fungal kingdom and highlight the interaction between genome defence mechanisms
and invasive DNA.
