lecture 1 - intro

Question 1

when are microbes considered disease causing pathogens?

Answer 1

when they infringe on our food supply and environment

Question 2

causal agents of plant disease?

Answer 2

1. fungi 2. oomycota 3. protozoa 4. bacteria 5. viruses

Question 3

which groups do the majority of fungi belong?

Answer 3

ascomycota and basidiomycota

Question 4

oospores and zoospores?

Answer 4

oospores are sexual resting stage. zoospores are asexual flagellated.

Question 5

potato blight?

Answer 5

it is an oomycota. caused irish potato famine in 1840s. forms lesions that stop photosynthesis. its genome is much larger than average oomycota so can evolve rapidly and adapt.

Question 6

rust fungi?

Answer 6

fungi that is specific for certain plants. there are many different species of. e.g. rust fungi for wheat, barley etc.
Again, genome is much bigger than average.

Question 7

in what ways are diseases aided?

Answer 7

mono cultures and agrochemicals. irrigation spreads pathogens. climate changes. importing of plant species.

Question 8

what does the molecular component consist of?

Answer 8

1. mendelian genetics 2. model orgs. 3. trans techniques 4.forward genetics 5. reverse genetics 6.dissection of sig pathways 7. gene expression profiling 8. proteomics and metabolomics

Question 9

characteristics of bacteria (disease)?

Answer 9

prefer warm climates. most cant colonise plant (propagate inside). most are gram negative.

Question 10

what are the gram positive bacteria that can cause disease? and why so?

Answer 10

spiroplasmas and phytoplasmas. they have lost their call wall. this is significant because plants have innate immunity to pos. explains the evolution of these neg like bacteria.

Question 11

soft rots?

Answer 11

produce cell wall degrading enz. nutrients are released.

Question 12

bacterial roots?

Answer 12

caused by bacteria that surround themselves with polysaccharides when they have invaded a wound to protect themselves from the plants defenses. the polysaccharides block the xylem and cause wilt,

Question 13

agrobacterium?

Answer 13

cause crown gall disease (tumours). used in plant transformation.

Question 14

pathogenicity islands? (PAI)

Answer 14

groups of genes important for plant pathogenicity. sometimes found in plasmids.
they have different ratio of g-c to the rest of the genome.

Question 15

difference between true pathogens an non-true?

Answer 15

true pathogens, when they are washed into a plant in water droplets, are able to colonise. Where as, non- true are not able to colonise. This is due to true having pathogenicity factors that allow them to proliferate in the plant.

Question 16

quorum sensing?

Answer 16

is the way bacteria communicate with each other. there are a number of genes that encode for quorum sensing signal molecules. if there are a lot of bacteria in an area there will be a lot of chemical produced (more bac=more chem) receptors on the bacteria detect that chem is above threshold. this leads to switching on of gene expression. such as turning off motility and switching on of pathogenicity factors.