- Innate immune response
The innate immune system is the first line of cellular defense in all classes of plants and animals against infection by other organisms. A number of signaling pathways in the nematode have been identified that act in this host response to microbial and fungal pathogens. Like other invertebrates, C. elegans does not have an adaptive immune system. However, unlike some invertebrates, C. elegans does not have any specialized cells dedicated to immune function. Triggering of the innate immune cellular response can occur in any tissue of the worm, and utilizes the any number of signaling pathways, which normally play roles in cell signaling events used during development or normal cell homeostasis.
- Mechanosensation
Mechanosensation converts mechanical energy into electrical signals allowing an organism to use physical cues from the environment or from internal sensors to affect its behavior. Mechanical stimuli are received through mechanosensory receptor neurons (MRNs). In C. elegans, there are 30 putative MRNs in hermaphrodites while an additional 52 MRNs are found in males. More than 40 of these male-specific MRNs are found in the male tail, hook, post-cloacal sensilla and spicule and are required for male mating. MRNs transmit electrical signals to other neurons through electrical or chemical synapses. MRNs may or may not have ciliated dendrite endings, which is some cases are exposed to the outside. Mechanical stimuli initiate as well as modulate many behaviors of the worm. MRNs allow the worm to respond to light touch, such as stroking with an eyelash as well as harsh touch, such as prodding with a pick.
- Intestine development
The C. elegans intestine is attached to the posterior pharynx and extends the length of the worm, ending at the rectum. This major organ of the worm consists of 20 large, polyploid epithelial cells arranged in pairs, forming a tube. The intestine is responsible for food digestion, nutrient absorption, and synthesizing and storing macromomlecules such as fat droplets and birefringent gut granules. The intestine also plays major roles in the rhythmic behavior of the defecation cycle as well as stress responses and lifespan.
- Unfolded protein response - Cytosolic
A change in activity of a cell (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of a protein that is not folded in its correct three-dimensional structure.
- Necrosis
Necrosis and apoptosis are contrasting modes of cell death. Whereas apoptotic cell death is associated with development and characterised by distinct stages of cell disassembly and engulfment, necrotic cell death is not a programmed cell fate and is characterised by an catastrophic disruption of the plasma membrane. Necrotic cell death is an important response to and in some cases, defense mechanism of, environmental or viral/bacterial pathogen assault.
- Regulation of rhythms and cycles
Any process regulating the generation and maintenance of physiological events that recur in measured regularity. Circadian, or 24-hour rhythms have not been characterized in C. elegans. However, ultradian rhythms, those that range from milliseconds to less than 24 hours, have been identified and studied in C. elegans. Such events, such as egg laying and defecation have exhibited periodicity in the nematode. Like circadian rhythms, these events exhibit temperature compensation and resetting through environmental stimuli.
- Locomotion
The movement of the animal in relation to its environment requires coordinating an awareness of environmental cues with the firing of neuronal circuitry affecting the simultaneous contraction and relaxation of opposing muscle groups. C. elegans exhibits many types of movement, the two major types are crawling and swimming. Each of these movements have been further characterized by dominant body shapes, trajectories, angles, speeds, etc., peculiar to the movement. Fundamental to survival of the worm is the ability to sense and move towards or away from different stimuli. Forward and backwards movements can be induced in the lab through the stimulation of the mechanosensory neural network.
- Response to stress
A stress response is any physical response to factors that upset the normal balance of a biological event. C. elegans nematodes are susceptible to many different environmental stressors that include changes in temperatures, exposure to high osmolarity, and changes in oxygen levels. Internal stressors include DNA damage, accumulation of unfolded proteins, and accumulation of reactive oxygen species. These stressors have been shown to have a strong impact on the lifespan of C. elegans. The regulation of stress responses in the worm are similar to that in other organisms and include modulations of pathways that control caloric intake, mitochondrial respiration, insulin/IGF-1 (IIS), and JNK (c-Jun N-terminal kinase) signaling.
- Cell death
The death of a cell is a highly regulated process that occurs frequently throughout development. Current research shows that there are four different ways a cell can die, programmed cell death, necrosis, autophagy, and cytotoxic cell death. Research in C. elegans pioneered the discovery of the molecular pathway responsible for programmed cell death. More recent work using this model organism has made headways into elucidating the genes involved in regulating and impacting these other methods of cell death. There is controversy as to whether or not cell death by autophagy has been observed in C. elegans animals; however, an aspect of autophagy, macroautophagy, has been reported.
- RNA processing
After transcription in the nucleus and before translation into a protein in the cytoplasm, newly transcribed RNA undergoes post-transcriptional modifications to become the mature mRNA. These modifications include the addition of a 5'cap and 3'poly A tail, and splicing out of noncoding introns. These modifications are needed for the RNA molecule to be protected against RNase activity as well as for it to be recognized by molecules that mediate translation into proteins. Splicing of the RNA is required to remove the portions of the message that are not supposed to be translated into the final protein product. In addition to intron and exon splicing of the pre-mRNA, ~70% of pre-mRNAs in C. elegans are trans-spliced to one of two different splice leader sequences, SL1 or SL2.