14. C. elegans III

Question 1

What are the components of the C. elegans hermaphrodite reproductive system?

Answer 1

Two U-shaped gonad arms, spermatheca, uterus, vulva

Each gonad arm includes a distal tip cell that produces germline cells, and oocytes mature along the gonad ‘conveyor belt’.

Question 2

What is the function of the uterine muscles in C. elegans?

Answer 2

Help squeeze eggs out

Uterine muscles wrap around the uterus.

Question 3

What are HSN neurons and their role in egg-laying?

Answer 3

Bilateral pair essential for normal egg-laying, release serotonin (5-HT)

Males do not have HSN neurons as they undergo programmed cell death.

Question 4

What type of synapses allow rapid ion flow between cells in the egg-laying circuit?

Answer 4

Gap junctions

Chemical synapses are shown as bars with circles in diagrams.

Question 5

Describe the egg-laying pattern of C. elegans.

Answer 5

Active phases (bursts of eggs laid), inactive phases (periods without egg-laying)

This pattern is neurally controlled.

Question 6

What happens to eggs in C. elegans in the absence of food?

Answer 6

Eggs are retained, worms become bloated with eggs (‘bag of worms’ phenotype)

When returned to food, worms resume egg-laying.

Question 7

What is the role of serotonin (5-HT) in egg-laying?

Answer 7

Drives transition from inactive to active egg-laying states

Released by HSN neurons; imipramine increases egg-laying.

Question 8

What are neuropeptides in the context of egg-laying regulation?

Answer 8

Function as neuromodulators, act through G-protein coupled receptors

They can function at distance (neurohormonally).

Question 9

What is the significance of the FLP-1 neuropeptide?

Answer 9

Important for adapting egg-laying to food availability

Expressed in interneurons (AVK and AVA) and required for serotonin’s effect on egg-laying.

Question 10

What does EGL-4 kinase do in C. elegans?

Answer 10

Required for food-dependent egg-laying adaptation

Involved in neuronal plasticity and can phosphorylate proteins affecting gene expression.

Question 11

How do amphid sensory neurons contribute to egg-laying behavior?

Answer 11

Detect food cues and signal to interneurons in the nerve ring

This information is relayed to HSN neurons to control egg-laying based on food availability.