A switch in the brain

Research from Greg Jefferis’s group in the LMB’s Neurobiology Division has uncovered a biological switch that determines which part of the fruit fly’s brain responds to pheromones, depending on whether the fruit fly is male or female. Previous studies have identified differences in brain structure between the sexes but this study, published in Cell, is the first description in any animal of a specific change in nerve cell wiring that reroutes information between male and female brains.

Sex pheromones are chemicals that allow male and female animals to communicate by smell. In some cases it is known that exactly the same pheromone molecule can produce distinct behavioural responses in both males and females. Since both sexes respond to the molecule, there appears to be a difference in brain perception rather than sensory detection. For example in fruit flies, a male sex pheromone called cVA can stimulate females to mate with a male, while repelling other males at the same time. Greg’s group have been investigating exactly how the processing of this pheromone differs between male and female brains.

Jonny Kohl, Aaron Ostrovsky and Shahar Frechter from Greg’s lab first identified and labelled two groups of nerve cells inside the fly brain that respond to pheromones using a green fluorescent protein. One group of nerve cells responded to pheromone only in male brains, while the second group responded only in females. This difference in response depended on a changeover switch that rerouted incoming pheromone information to different groups of olfactory neurons in male and female flies.

Further experiments showed that this switch is set by the action of a control gene, called fruitless. Genetic manipulations allowed them to make a small number of nerve cells male in an otherwise female brain; this helped to pin point the exact location in the brain and the gene controlling the switch. The fruitless gene had previously been shown to control fruit flies’ sexual behaviour but exactly how it could achieve this through changes in brain wiring was unknown.

 One of the biggest challenges in biology today is to understand how the pattern of connections between individual nerve cells allows the brain to process and store information and respond to the outside world. Looking at the differences between the male and female brains of a species is one powerful approach to study the relationships between brain wiring and behaviour. Until now it has proven very difficult to identify specific and reproducible differences in brain wiring and understand how they could alter the flow of information between male and female brains. This research has now shown how this occurs in flies. Sex differences in brain structure and behaviour have been documented in organisms from worms to humans. This study suggests a general mechanism by which males and females could perceive or interpret the same stimulus, such as smell, differently. The same form of genetic regulation of wiring might also be at the origin of behavioural differences across species.

This work was supported by the Medical Research Council, European Research Council, and an EMBO Post-doctoral Fellowship.

Images: Gregory Jefferis. jefferis@mrc-lmb.cam.ac.uk Personal group site

Further References:

Paper in Cell
Greg’s group page



ORIGINAL: MRC
20th December, 2013
Copyright © 2013 MRC Laboratory of Molecular Biology.

The Blob Attacks: Gooey Slime Mold is an Example of Leaderless Motion

ORIGINAL: Decoded Science

BY TRICIA EDGAR

OCTOBER 29, 2011

"Dog Vomit" slime mold is also known as Fuligo septica. Image Credit: Interro

It’s creeping, creeping, creeping toward a log near you. Perhaps it’s hanging out in the bark mulch, slowly eating its way along. The blob is here in the forests around you, and its name is slime mold.

At first glance, a slime mold appears to be a very unassuming collection of slimy bits that are often brown or yellow. It can look rather unfortunate. One of the world’s most common slime molds is also known as the “Dog Vomit” slime mold.

What Are Slime Molds?

For a long time, slime molds were identified as fungi. They appear to be fungi. They sit on a log, munching away on detritus rather than making their own food. They reproduce through spores. However, there is one big difference between slime molds and fungi: slime molds move.

A moving plant? Or is it an animal? Well, slime molds find those human-created categories to be inadequate to their amazing cellular properties. A slime mold streams over bark and leaves, engulfing them. While it moves like an animal, it acts like a fungus. A slime mold consumes dead material. However, a slime model does not have hard chitin in its cell walls, so it’s able to get together in large cytoplasmic masses.

Unlike fungi, slime molds do not have hard cell walls. Image Credit: stoon

What is a slime mold, if not a fungus? The slime mold is made out of a conglomeration of single-celled life forms called protists.

Different Types of Slime Molds

Some slime molds are naturally gregarious. Plasmodial slime molds (cue Ghostbusters soundtrack) consist of single-celled slime molds that get together in a cytoplasm gel.

Other slime molds use the social media of the slime world to get together and have a feeding frenzy. These cellular slime molds are called slugs when they are alone. Each slug leaves a chemical trail as it moves around a log. When a slug encounters another pheromone trail, it follows it. Eventually, the slugs all get together in an area that is optimal for feeding.

When slime molds get together, the party begins. They form a structure called a pseudoplasmodium that moves over logs, bark, and soil at a rate of one inch per day. When food is particularly abundant, the slime mold changes. Some of the slugs form a base, while others become spores and stalks. The slime mold forms reproductive structures as a whole organism, even though it is made out of individual parts.

Slime Mold Motivations

Slime molds are relatively simple. Each slug seeks the same thing: namely, food. They also need moisture to survive. They can communicate their success to other slugs, and this chemical communication ultimately results in a collection of slime mold cells that becomes something quite different from its parts.

• Microbe World. Slime Molds. Accessed October 29, 2011.
• University of California Museum of Paleontology, Berkeley. Introduction to the Slime Molds. Accessed October 29, 2011.
• Nature. Cellular Memory Hints at the Origins of Intelligence. (2008). Accessed October 29, 2011.
• Adamatzky, A., Jones, J. International Journal of Bifurcation and Chaos. Road Planning With Slime Mould. (20101). Accessed October 29, 2011.