CSB452 LECTURE 1
PAMP Triggered Immunity (PTI)
Infiltration bypass stomata while spray allow coating. Vacuum infiltration is more uniform.
Pathogen Associated Molecular Pattern can be f lagellin, lipopolysaccharides of gram-negative bacteria,
chitin, ergosterol, transglutaminase from fungi, or bacterial translation elongation factor EF-TU.
Induces MAPK cascade, transcription of PR genes and deposition of b1-3-glucn callose at infection site
visualized by anal ine blue dye.
PAMP and Receptor Identification
PAMP cause plant to uptake H
, release K
and increase pH causing alkalinization of media.
Apply bacterial protein extract separated by SDS-PAGE and see which band causes alkalinization.
When f lg22 is applied to plant before infiltration, bacterial growth decreased afterwards.
EMS mutagenesis of seeds. Plants are then selfed to produce homozygous recessive mutant.
WT seedling exposed to f lg22 show stunted growth, so s creen for insensitive mutant that grows
nor mally wit h f lg22. Cross mutant to other ecotype for mapping.
Identified f ls2-0 and f ls2-24 mutants. They do no accumulate callose and are more susceptible to
infection, growth and invasion into tissue using spray method.
Infiltration method caused no difference showing f ls2 is not involved in post invasion defence.
Fls2 is a pattern recognition receptor (PRR) with LRR and kinase domain that activate MAPK cascade.
mutant with no effectors, PTI is triggered by f ls2 leading to callose deposition.
PAMP, LPS polysaccharide of bacteria or f lg22 induces stomata closure.
cluster around open stomata and produce polyketide toxin coronatine to prevent PAMP
induced stomata closure. DC3000 initially cause closure but after 3hrs stomata reopens.
Flg22 or LPS + coronatine keeps stomata open.
DC3118 lacking coronatine does not reopen stomata, goes less into leaf and grows less intra-leaf when
sprayed onto leaf.
DC3118 grows the same as DC3000 when pressure infiltrated into leaf, showing coronatine does not