Maintenance of Acquired Immunity

Question 1

What is priming of SA inducible defence genes?

Answer 1

• Sprayed SA onto leaves
• 28 days later, pathogen challenge
• Higher PR-1 levels (defence gene)
• Plants vaccinated at seedling stage showed stronger induction compared to control

Question 2

What is priming of JA inducible genes against herbivory?

Answer 2

• JA sprayed onto leaves
• 21 days later, JA challenge
• Feeding on second challenge is reduced
• Higher levels of VSP2 (protein affects performance of caterpillars)

Question 3

Is induced resistance heritable?

Answer 3

Yes, after severe disease stress
Parent plants were exposed to a high level of P. syringae
Progeny from infected plants had a higher frequency of more resistant plants
Heritable induced resistance

Question 4

What epigenetic mechanism supports heritable induced resistance (h-IR)?

Answer 4

Changes in DNA methylation at transposons and regulatory sites

Question 5

What enzyme is essential for h-IR?

Answer 5

ROS 1 (a DNA demethylase)

Question 6

What happens in ros1 mutants?

Answer 6

They show hyper-methylation and enhanced heritable resistance, even without severe stress

Question 7

Is h-IR stable across all progeny?

Answer 7

No, it is highly variable and occurs only when parental plants experience significant stress

Question 8

What does DNA methylation do in plants?

Answer 8

Compacts chromatin and silences genes by blocking transcription

Question 9

What regulates DNA methylation?

Answer 9

Methyltransferases (adds methyl groups)
Demethylases (like ROS1, removes methyl groups)

Question 10

What causes variation in susceptibility in genetically identical lines?

Answer 10

Epigenetic differences in DNA methylation patterns, especially at transposons

Question 11

What are epiRILs?

Answer 11

Epigenetic recombinant inbred lines
Genetically identical but epigenetically different

Question 12

What are resistant epiRILs?

Answer 12

epiRILs primed to quickly express defence genes without affecting growth

Question 13

How can epigenetic priming be introduced artificially?
What is the outcome of doing this?

Answer 13

Using estradiol (E2)-inducible ROS1-YFP expression to reduce DNA methylation

Outcome: long-lasting resistance to biotrophic pathogens, with temporary growth effects that plants recover from

Question 14

What is epigenetic priming?

Answer 14

Preparing the genome for future expression of genes in response to a particular cue or stimulus