Sex- and Gamete-Specific Patterns of X Chromosome Segregation in a Trioecious Nematode

Sophie Tandonnet, Maureen C Farrell, Georgios D Koutsovoulos, Mark L Blaxter, Manish Parihar, Penny L Sadler, Diane C Shakes, Andre Pires-daSilva

Research output: Contribution to journalArticlepeer-review

Abstract

Three key steps in meiosis allow diploid organisms to produce haploid gametes: (1) homologous chromosomes (homologs) pair and undergo crossovers; (2) homologs segregate to opposite poles; and (3) sister chromatids segregate to opposite poles. The XX/XO sex determination system found in many nematodes [1] facilitates the study of meiosis because variation is easily recognized [2-4]. Here we show that meiotic segregation of X chromosomes in the trioecious nematode Auanema rhodensis [5] varies according to sex (hermaphrodite, female, or male) and type of gametogenesis (oogenesis or spermatogenesis). In this species, XO males exclusively produce X-bearing sperm [6, 7]. The unpaired X precociously separates into sister chromatids, which co-segregate with the autosome set to generate a functional haplo-X sperm. The other set of autosomes is discarded into a residual body. Here we explore the X chromosome behavior in female and hermaphrodite meioses. Whereas X chromosomes segregate following the canonical pattern during XX female oogenesis to yield haplo-X oocytes, during XX hermaphrodite oogenesis they segregate to the first polar body to yield nullo-X oocytes. Thus, crosses between XX hermaphrodites and males yield exclusively male progeny. During hermaphrodite spermatogenesis, the sister chromatids of the X chromosomes separate during meiosis I, and homologous X chromatids segregate to the functional sperm to create diplo-X sperm. Given these intra-species, intra-individual, and intra-gametogenesis variations in the meiotic program, A. rhodensis is an ideal model for studying the plasticity of meiosis and how it can be modulated.

Original languageEnglish
Pages (from-to)93-99.e3
Number of pages11
JournalCurrent biology : CB
Volume28
Issue number1
DOIs
Publication statusPublished - 8 Jan 2018

Keywords

  • meiosis
  • lack of recombination
  • X chromosome
  • Auanema rhodensis
  • father-to-son X transmission
  • C. elegans
  • non-disjunction
  • SB347

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