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Deviations in the Z:A ratio disrupt sexual development in the eri silkmoth, Samia cynthia ricini.

Atsuo YoshidoFrantišek Marec
Published in: Genetics (2023)
Moths and butterflies (Lepidoptera) have sex chromosome systems with female heterogamety, and two models, W-dominance and Z-counting, have been proposed to determine sex. The W-dominant mechanism is well known in Bombyx mori. However, little is known about the Z-counting mechanism in Z0/ZZ species. We investigated whether ploidy changes affect sexual development and gene expression in the eri silkmoth, Samia cynthia ricini (2n = 27♀/28♂, Z0♀/ZZ♂). Tetraploid males (4n = 56, ZZZZ) and females (4n = 54, ZZ) were induced by heat and cold shock, and then triploid embryos were produced by crosses between diploids and tetraploids. Two karyotypes (3n = 42, ZZZ and 3n = 41, ZZ) were identified in triploid embryos. Triploid embryos with three Z chromosomes showed male-specific splicing of the S. cynthia doublesex (Scdsx) gene, whereas two-Z triploid embryos showed both male- and female-specific splicing. From larva to adult, three-Z triploids showed a normal male phenotype, except for defects in spermatogenesis. However, abnormal gonads were observed in two-Z triploids, which showed both male- and female-specific Scdsx transcripts not only in the gonads but also in somatic tissues. Two-Z triploids were thus obviously intersexes, suggesting that sexual development in S. c. ricini depends on the Z:A ratio and not only on the Z number. Moreover, mRNA-seq analyzes in embryos showed that relative levels of gene expression are similar between samples with different doses of Z chromosomes and autosome sets. Our results provide the first evidence that ploidy changes disrupt sexual development but have no effect on the general mode of dosage compensation in Lepidoptera.
Keyphrases
  • gene expression
  • mental health
  • dna methylation
  • copy number
  • single cell
  • transcription factor
  • heat stress
  • atomic force microscopy
  • binding protein