Week 4: Nematodes Flashcards
1
Q
body plan
A
- unsegmented (1 body part)
- bilateral symmetry
- tube within tube design
- distinct males and females
- mostly composed of gut and reproductive structures
2
Q
plant parasitic nematodes
A
- commonly transmitted in soil
- have cuticle to protect from pathogens in the soil
- some have become endoparasites for protection
- many are capable of cryptobiosis: suspend metabolism then reactivate when they contact a host factor
3
Q
parallel evolution of the stylet
A
- have specialized feeding needle called a stylet
- it is an adaptation that allowed them to become parasitic
- has evolved at least 4 times
- different species have all independently gained a stylet
- parallel evolution is when two lineages solve a problem independently using the same solution
4
Q
sedentary endoparasites
A
- most damaging
- stays in same spot
- adult male exits the root when it is fully grown
- adult female grows so large that the posterior end will go out the root and it can reproduce with adult males that have exited
- the female then dies and forms a cyst to protect the dormant eggs
5
Q
migratory endoparasites
A
- travel up and down the root and feed at different sites
- leave dead material behind
- can enter the root at any stage, depends on when they find a host
6
Q
nematode survival strategies
A
- code for a large number of effector proteins that manipulate host immunity
- reprogram the host to form feeder cells
- cyst formation: dead body of female forms a protective cyst around the eggs
7
Q
Feeding cells
A
- make it easy for the nematode to remain sedentary while feeding
- cyst nematodes induce syncytia
- induction of an initial feeding cell
- the feeding cell fuses with 100s of other cells to form syncytia (single cell with lots of nuclei)
8
Q
main types of plant nematodes
A
- ectoparasites: adapted to have very long stylets, avoid immune system but face predators and abiotic stress
- semi-endoparasite: partially penetrate plant
- endoparasite: sedentary and migratory
9
Q
How does nematode induce feeder cell creation
A
- has specific effectors that modulate plant growth hormone
- turns off immunity and turns on rapid growth
- produces molecular mimic of a peptide that tell a cell to be a stem cell and causes it to grow rapidly
- modulate cell wall structure to allow for fusion (not sure exactly how they do it)
10
Q
Biological nematode control
A
- breed resistant crops or switch crops
- biocontrol agents: bacteria that kill nematodes, too expensive
11
Q
cultural nematode control
A
- what we mostly rely on
- crop rotation with non-host plant: reduces infection but does not fully get rid of it
- use clean stock to prevent transfer between fields
12
Q
chemical nematode control
A
- fumigants are banned
- most treatments are too expensive
- nursery soil can be treated to make it clean
13
Q
Strongyloides (threadworms)
A
- human nematode
- lives at at surface of the skin
- causes skin infection, usually only in immuno-compromised individuals
14
Q
Hookworms
A
- human nematode
- soil transmitted
- deposited from human feces into the soil
- if you walk barefoot in these regions, worm will go into your foot and travel up your foot into you digestive systems where they will deposit their eggs
15
Q
Pinworms
A
- human nematode
- high prevalence in developed countries
- eggs live in the gut and lay at night
- mostly in kids
- hand to mouth disease
