Phenotypic differences between sexes are often mediated by differential expression and alternative splicing of genes. However, the mechanisms that regulate these expression and splicing patterns remain poorly understood. The mealybug, Planococcus citri, displays extreme sexual dimorphism and exhibits an unusual instance of sex-specific genomic imprinting, paternal genome elimination (PGE), in which the paternal chromosomes in males are highly condensed and eliminated from the sperm. Planococcus citri has no sex chromosomes and both sexual dimorphism and PGE are predicted to be under epigenetic control. We recently showed that P. citri females display a highly unusual DNA methylation profile for an insect species, with the presence of promoter methylation associated with lower levels of gene expression. Here, we therefore decided to explore genome-wide differences in DNA methylation between male and female P. citri using whole-genome bisulphite sequencing. We identified extreme differences in genome-wide levels and patterns between the sexes. Males display overall higher levels of DNA methylation which manifest as more uniform low levels across the genome. Whereas females display more targeted high levels of methylation. We suggest these unique sex-specific differences are due to chromosomal differences caused by PGE and may be linked to possible ploidy compensation. Using RNA-Seq, we identify extensive sex-specific gene expression and alternative splicing, but we find no correlation with cis-acting DNA methylation.

中文翻译：

---

具有极端性别二态性和父系基因组消除的物种中的性别特异性表达和 DNA 甲基化

两性之间的表型差异通常由基因的差异表达和可变剪接介导。然而，调节这些表达和剪接模式的机制仍然知之甚少。粉蚧，柑橘扁平球菌，表现出极端的性别二态性，并表现出不寻常的性别特异性基因组印记，父系基因组消除（PGE），其中男性的父系染色体高度浓缩并从精子中消除。柑橘扁平球菌没有性染色体，预计两性二态性和 PGE 都受表观遗传控制。我们最近证明了P。 柑橘雌性在昆虫物种中表现出极不寻常的 DNA 甲基化谱，启动子甲基化的存在与较低水平的基因表达相关。在这里，我们因此决定探索雄性和雌性P之间 DNA 甲基化的全基因组差异。 柑橘使用全基因组亚硫酸氢盐测序。我们发现了两性之间全基因组水平和模式的极端差异。男性表现出总体较高水平的 DNA 甲基化，表现为整个基因组中更均匀的低水平。而女性则表现出更有针对性的高水平甲基化。我们认为这些独特的性别特异性差异是由于 PGE 引起的染色体差异，并且可能与可能的倍性补偿有关。使用 RNA-Seq，我们确定了广泛的性别特异性基因表达和可变剪接，但我们发现与顺式作用 DNA 甲基化没有相关性。