Intragenomic conflict under paternal genome elimination
García De La Filia, Andrés
Genetic systems are extraordinarily variable across taxa, not only among large taxonomic groups but also between closely related species. The causes of this diversity are not fully understood, remaining a fundamental question in evolutionary biology. Genomic conflicts arising during reproduction might play an important role in shaping the striking diversity of reproductive strategies across life. Among these is paternal genome elimination (PGE), a form of haplodiploidy which has independently evolved several times in arthropods. Under PGE, males are diploid but transmit maternally-inherited chromosomes only. Moreover, in many forms of PGE, paternal chromosomes are silenced early in development. Due to the unequal inheritance patterns of PGE, mothers enjoy a transmission advantage through their sons, generating a strong scope for intragenomic conflict between paternally- and maternally-inherited genomes within males. However, empirical evidence for such conflict is lacking. In this thesis, I study whether paternal genomes can resist silencing and elimination in two PGE species: the citrus mealybug Planoccocus citri (Hemiptera: Pseudococcidae), where paternal chromosomes are silenced, and the human louse Pediculus humanus (Phthiraptera: Pediculidae), where PGE was recently discovered. I show that elimination of paternal chromosomes is leaky in both species and determine genome-wide patterns of parent-of- origin-specific expression to reveal the extent of paternal genome expression. Together, my findings offer a solid empirical ground to further explore the role of conflict in evolution of PGE and illustrate how this genetic system can impact different biological processes, such as hybrid incompatibilities and evolution of resistance.