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Stimulating and Analyzing Adult Neurogenesis in the Drosophila Central Brain
Published on: October 8, 2021
Male killing Spiroplasma preferentially disrupts neural development in the Drosophila melanogaster embryo
Jennifer Martin1, Trisha Chong, Patrick M Ferree
1W. M. Keck Science Department, Claremont McKenna, Scripps, and Pitzer Colleges, Claremont, California, United States of America.
Abstract:
Male killing bacteria such as Spiroplasma are widespread pathogens of numerous arthropods including Drosophila melanogaster. These maternally transmitted bacteria can bias host sex ratios toward the female sex in order to 'selfishly' enhance bacterial transmission. However, little is known about the specific means by which these pathogens disrupt host development in order to kill males. Here we show that a male-killing Spiroplasma strain severely disrupts nervous tissue development in male but not female D. melanogaster embryos. The neuroblasts, or neuron progenitors, form properly and their daughter cells differentiate into neurons of the ventral nerve chord. However, the neurons fail to pack together properly and they produce highly abnormal axons. In contrast, non-neural tissue, such as mesoderm, and body segmentation appear normal during this time, although the entire male embryo becomes highly abnormal during later stages. Finally, we found that Spiroplasma is altogether absent from the neural tissue but localizes within the gut and the epithelium immediately surrounding the neural tissue, suggesting that the bacterium secretes a toxin that affects neural tissue development across tissue boundaries. Together these findings demonstrate the unique ability of this insect pathogen to preferentially affect development of a specific embryonic tissue to induce male killing.
Insights
Male-killing Spiroplasma bacteria disrupt nervous system development in male Drosophila melanogaster embryos, leading to male death. This pathogen preferentially targets neural tissue, causing abnormal axon formation and skewed sex ratios.
Area of Science:
- Microbiology
- Developmental Biology
- Genetics
Background:
- Male-killing bacteria, such as Spiroplasma, are common pathogens in arthropods.
- These bacteria are maternally transmitted and bias host sex ratios toward females to enhance their own transmission.
- The precise mechanisms by which these bacteria induce male lethality during host development are not well understood.
Purpose of the Study:
- To investigate the specific developmental disruptions caused by a male-killing Spiroplasma strain in Drosophila melanogaster embryos.
- To determine the affected tissues and the localization of the bacteria within the host embryo.
Main Methods:
- Comparative analysis of male and female Drosophila melanogaster embryos infected with Spiroplasma.
- Histological examination of nervous tissue and other embryonic tissues.
- Bacterial localization studies using microscopy.
Main Results:
- Spiroplasma infection severely disrupts nervous tissue development in male embryos, but not in female embryos.
- While neuroblast differentiation occurs, neurons exhibit abnormal packing and axon formation in males.
- Spiroplasma localizes to the gut and surrounding epithelium, not directly within neural tissue, suggesting toxin-mediated effects.
Conclusions:
- Male-killing Spiroplasma preferentially targets and disrupts embryonic neural tissue development in a sex-specific manner.
- The bacteria likely secrete a toxin that affects neural development across tissue boundaries.
- This targeted disruption of a specific tissue is the mechanism by which Spiroplasma induces male killing and skews host sex ratios.
