Plants perceive effector molecules of a pathogen and mount a series of events that lead to the activation of a defense response. Following statements are made with respect to events that occur within a few minutes of the effector perception.

A. Transient change in the ion permeability of the plasma membrane.
B. Efflux of K⁺ and Cl⁻ ions from the cell.
C. Influx of Ca²⁺ and H⁺ ions into the cell.
D. Influx of K⁺ and Cl⁻ ions into the cell and efflux of Ca²⁺ and H⁺ from the cell.

Which one of the following options represents the combination of all correct statements?

Correct option is A

Explanation:

1. Statement A: Transient change in the ion permeability of the plasma membrane.

   • This is correct. When plants perceive pathogen effectors, one of the immediate responses is the change in the ion permeability of the plasma membrane. This leads to the movement of ions across the membrane, which plays a key role in activating defense responses.

2. Statement B: Efflux of K⁺ and Cl⁻ ions from the cell.

   • This is correct. In response to pathogen detection, there is an efflux of K⁺ (potassium) and Cl⁻ (chloride) ions from the plant cell. This efflux contributes to the generation of an ionic imbalance that can help activate defense mechanisms.

3. Statement C: Influx of Ca²⁺ and H⁺ ions into the cell.

   • This is correct. Following pathogen perception, there is an influx of Ca²⁺ (calcium) and H⁺ (protons) ions into the cell. Calcium influx is crucial for signaling in plant defense, while H⁺ influx is often associated with acidification of the cell wall during defense responses.

4. Statement D: Influx of K⁺ and Cl⁻ ions into the cell and efflux of Ca²⁺ and H⁺ from the cell.

   • This is incorrect. While K⁺ and Cl⁻ may move into the cell under certain conditions, the general pattern during pathogen-induced responses is the efflux of these ions, not the influx. Also, the efflux of Ca²⁺ and H⁺ ions is not typically associated with this immediate response; rather, there is a rapid influx of Ca²⁺ and H⁺ into the cell.

Information Booster:

1. Ion permeability of the plasma membrane changes transiently in response to pathogen perception. This is a critical step in triggering the defense response.
2. Efflux of K⁺ and Cl⁻ ions occurs immediately after pathogen detection, leading to an imbalance in ion concentration and triggering signaling pathways.
3. Influx of Ca²⁺ and H⁺ ions into the cell is a rapid response to pathogen recognition and plays a crucial role in activating downstream defense mechanisms, including the production of reactive oxygen species and the activation of defense genes.
4. The influx of K⁺ and Cl⁻ ions into the cell and efflux of Ca²⁺ and H⁺ ions is not a typical early response in pathogen defense.