Biology subjects

de la Filia, A. G.

Publications and source records attributed to de la Filia, A. G..

3 recordsLinked to original sources

bioRxiv2023

Lack of paternal silencing and ecotype-specific expression in head and body lice hybrids.

Paternal genome elimination (PGE) is a non-Mendelian inheritance system in which males develop from fertilised eggs but their paternally-inherited chromosomes are eliminated before or during spermatogenesis. Therefore, PGE males only transmit their maternally inherited set of chromosomes to their offspring. PGE has been described in numerous arthropod species, many of which are pests or parasites, posing a severe economic burden on crop production and/or with implications for human health. In order to understand how PGE has evolved on the molecular level, to potentially develop novel control strategies, we need to examine species which display basal forms of PGE. The human louse, Pediculus humanus, represents an ideal model system to understand the molecular underpinnings of PGE. In this study we analysed parent-of-origin allele specific expression patterns in male offspring of crosses between head and body lice ecotypes. We have shown that hybrid adult males of P. humanus display biparental gene expression, which constitutes the first known case of a species with PGE in which genetic activity of paternal chromosomes in the soma is not affected by embryonic heterochromatinization or (partial or complete) elimination. We have also identified maternally-biased genes (potentially imprinted genes) which may be involved in the elimination of paternal chromosomes during spermatogenesis. Finally, we have identified genes which show ecotype-specific expression bias. Given the low genetic diversity between ecotypes this is suggestive for a role of epigenetic processes in ecotype differences. These findings have implications for models of pediculicide resistance in human lice and for the development of novel epigenetic-mediated control strategies.

evolutionary biology↗

bioRxiv2021

The B chromosome of Pseudococcus viburni: a selfish chromosome that exploits whole-genome meiotic drive

Meiosis, the key process underlying sexual reproduction, is generally a fair process: each chromosome has a 50% chance of being included into each gamete. However in some organisms meiosis has become highly aberrant with some chromosomes having a higher chance of making it into gametes than others. Yet why and how such systems evolve remains unclear. Here we study the unusual reproductive genetics of mealybugs, in which only maternal-origin chromosomes are included into the gametes during male meiosis, while paternally-derived chromosomes degrade. This "whole genome meiotic drive" occurs in all males and is evolutionarily conserved. However one species - the obscure mealybug Pseudococcus viburni - has a segregating B chromosome that increases in frequency by escaping paternal genome elimination. Here we present whole-genome and gene expression data from laboratory lines with and without B chromosomes. These data allow us to identify B-linked sequences including >70 protein-coding genes as well as a B-specific satellite repeat that makes up a significant proportion of the chromosome. We also used these data to investigate the evolutionary origin of the B chromosome. The few paralogs between the B and the core genome are distributed throughout the genome, showing that it is unlikely that the B originated through a simple duplication of one of the autosomes. We also find that while many of the B-linked genes do not have paralogs within the P.viburni genome, but they do show orthology with genes in other hemipteran insects suggesting that the B might have originated from fission of one of the autosomes, possibly followed by further translocations of individual genes. Finally in order to understand the mechanisms by which the B is able to escape elimination when paternally-derived we generated gene expression data for males and females with and without B chromosomes. We find that at the developmental stage when meiosis is taking place only a small number of B-linked genes show significant expression. Only one gene was significantly over-expressed during male meiosis, which is when the drive occurs: a acetyltransferase involved in H3K56Ac, which has a putative role in meiosis and is therefore a promising candidate for further studies. Together, these results form a promising foundation for studying the mechanisms of meiotic drive in a system that is uniquely suited for this approach.

evolutionary biology↗

bioRxiv2020

Males that silence their father's genes: genomic imprinting of a complete haploid genome

Genetic conflict is considered a key driver in the evolution of new reproductive and sex determining systems. In particular, reproductive strategies with non-Mendelian inheritance, where parents do not contribute equally to the genetic makeup of their offspring. One of the most extraordinary examples of non-Mendelian inheritance is paternal genome elimination (PGE), a form of haplodiploidy which has evolved repeatedly across arthropods. Under PGE, males are diploid but only transmit maternally-inherited chromosomes to their offspring, while the paternal homologues are excluded from sperm. This asymmetric inheritance is thought to have evolved through an evolutionary arms race between paternal and maternal genomes over transmission to future generations. In several clades with PGE, such as the mealybugs (Hemiptera: Pseudococcidae), paternal chromosomes are not just eliminated from sperm, but also heterochromatinised early in development and thought to remain inactive. Such paternal genome silencing could alleviate genetic conflict between paternal alleles over transmission. However, it is unclear if paternal chromosomes are indeed genetically inert in both soma and germline. Here, we present a parent-of-origin allele-specific transcriptome analysis in male mealybugs. We show that expression is globally biased towards the maternal genome, but detect activity of paternal chromosomes in both somatic and reproductive tissues. Up to 70% of somatically-expressed genes are to some degree paternally-expressed. However, paternal genome expression is much more restricted in the testis, with only 20% of genes showing paternal contribution. Finally, we show that the patterns of parent-of-origin-specific gene expression are remarkably similar across genotypes and that those genes with biparental expression show elevated rates of molecular evolution. Our results provide the clearest example yet of genome-wide genomic imprinting (parent-of-origin specific gene expression) in insects. Furthermore, it enhances our understanding of PGE, which will aid future empirical tests of evolutionary theory regarding the origin of this unusual reproductive strategy.

evolutionary biology↗