Environment & Biodiversity

GE marvel: parthenogenesis in Drosophila fruit flies

  • Researchers from Cambridge University and the California Institute of Technology have completed a stunning feat: they transformed a sexually reproducing fruit-fly species into one capable of asexual reproduction using minimal genetic alterations. 

About Drosophila

  • Drosophila is a genus of two-winged flies, also known as fruit flies, employed in evolutionary and developmental research.
  • It is a genus of flies in the Drosophilidae family, and its members are commonly referred to as “small fruit flies,” pomace flies, vinegar flies, or wine flies, owing to the tendency of many species to loiter around overripe or rotting fruit.
  • The Drosophila melanogaster genome contains 200,000,000 base pairs dispersed across four DNA molecules, encoding approximately 13,600 genes.
  • For the past century, it has been one of the most commonly used and preferred model organisms in biological study around the world. 

Parthenogenesis (asexual reproduction) in the Drosophila family

  • Parthenogenesis Discovery: Parthenogenesis, or fatherless reproduction, was discovered in Drosophila mangebeirai, a species composed entirely of females.
  • Facultatively Parthenogenetic Species: Approximately 76% of sexually reproducing species, including Drosophila mercatorum, were discovered to have facultative parthenogenesis, which occurs when isolated virgin females hatch eggs that develop into young without male fertilisation.
  • Canonical Species: The standard research species, Drosophila melanogaster, reproduces only sexually.

The Genetic Basis of Parthenogenesis

  • Identifying Relevant Genes: Researchers sought to identify genes that promote parthenogenetic development in Drosophila mercatorum eggs and then change the Drosophila melanogaster genome correspondingly.
  • RNA Sequencing: Researchers used RNA sequencing to identify 44 genes in parthenogenetic D. mercatorum eggs that expressed differently than sexually reproducing eggs.

Engineering Asexual Reproduction

  • Genetic Modifications: Researchers altered the expression levels of specific genes in the Drosophila melanogaster genome to match the results seen in parthenogenetic D. mercatorum eggs.
  • Outcome: Genetic changes, such as overexpression of the pologene and Myc genes and decreased expression of the Desat2 gene, resulted in roughly 1.4% of D. melanogaster eggs undergoing parthenogenesis, with viable offspring reaching adulthood.
  • Parthenogenetically created adult flies were able to mate with males and produce offspring, demonstrating facultative parthenogenesis in a strictly sexually reproducing species. 

Mechanism involving polar bodies

  • Polar bodies, which are byproducts of chromosome transmission processes after fertilisation, have been linked to the initiation of embryonic development in unfertilized eggs.
  • Efficiency Changes: Genetic alterations most likely hampered the sequestration and disposal of polar bodies, allowing them to replace the absent male pronucleus and commence embryonic development. 

Implications of Pest Control

  • Pest Management: Expresses concern about unforeseen repercussions of pest management technologies based on sterilisation or genome editing.
  • Genetic engineering enables genetic manipulation in model organisms, which aids research into gene drive technology and population management.
  • Conservation Biology provides insights into species adaptation and the possible effects of genetic interventions on natural populations. 

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