Constitutive PR protein expression in transgenic plants — what broad effect has been observed?

Introduction / Context:
Pathogenesis-related (PR) proteins such as chitinases and glucanases are induced during plant defense. Transgenic plants engineered to express PR proteins constitutively can alter baseline immunity and interact with broader defense signaling networks (e.g., systemic acquired resistance).

Given Data / Assumptions:

• Question focuses on the overall outcome of constitutive PR protein expression.
• Defense is multifactorial; single PR proteins rarely act as universal cures.
• Defense networks can be primed or cross-activated.

Concept / Approach:

Constitutive PR expression may enhance resistance by directly degrading pathogen cell walls and by signaling that upregulates additional antimicrobial pathways. The most consistent, generalizable statement is that PR proteins can trigger or prime broader defense responses rather than alone providing universal, high-level protection against diverse pathogens.

Step-by-Step Solution:

Verification / Alternative check:

Studies report that PR protein expression can prime SAR-like responses and enhance resistance spectrum modestly to moderately, depending on the PR and pathogen.

Why Other Options Are Wrong:

“No protection” contradicts empirical data; “single PR gives high-level protection to many pathogens” is overstated; the “two PR proteins provide some protection” is too narrow and not a general principle.

Common Pitfalls:

Overgeneralizing from specific case studies; protection levels vary with PR type, promoter, and pathogen.

Final Answer:

PR proteins can trigger additional antimicrobial defense pathways in the plant