Question

Given below are two statements:
Statement I: Mutations in Avr-gene are beneficial for the pathogens.
Statement II: Mutation in the effector coding gene would improve the perception of effectors by plant cytoplasmic receptor.

In light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

To evade R-gene-mediated immunity:
- Pathogens must mutate or delete their Avr/effector genes.
- This renders them "invisible" to the plant's cytoplasmic R-protein.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Avirulence ($Avr$) genes encode effectors that are recognized by plant resistance ($R$) gene products, triggering Effector-Triggered Immunity (ETI), which results in a hypersensitive response that stops disease progression.
Detailed Explanation:
Let us evaluate both statements:
Statement I:
An active $Avr$ gene leads to the pathogen's recognition by a resistant host harboring the matching $R$ gene.
If a mutation occurs in the $Avr$ gene (such as deletion, point mutation, or frame-shift), the plant $R$-protein can no longer bind or detect the effector.
This allows the pathogen to escape host surveillance and successfully colonize the host, causing disease.
Thus, mutations in $Avr$ genes that evade recognition are beneficial for the pathogen's survival and virulence.
Therefore, Statement I is correct.
Statement II:
Mutations in effector-coding genes (including $Avr$ genes) typically disrupt the binding interface or conformation of the effector, which prevents or reduces perception by plant cytoplasmic $R$-receptors.
An increase or improvement in perception would trigger a strong host hypersensitive response and kill the pathogen, which is highly disadvantageous to the pathogen.
Therefore, Statement II is incorrect.

Step 2: Final Answer:
Statement I is correct, and Statement II is incorrect.
This corresponds to Option (C).