Correct option is D
Explanation:
Let's evaluate each statement regarding defense signaling pathways in plants:
A. When JA-Ile levels rise, the JAZ proteins interact with COI1 protein and get degraded by 26S proteasomal pathways.
This statement is correct. Jasmonic acid (JA) is a plant hormone involved in defense responses, especially against pathogen and herbivore attacks. JA-Ile (Jasmonoyl-Isoleucine) is the bioactive form of JA. JAZ proteins interact with COI1 protein (CORONATINE INSENSITIVE1), and in the presence of JA-Ile, JAZ proteins are targeted for degradation by the 26S proteasome pathway, thereby releasing the transcription factors that initiate defense responses. This is a key part of the JA-mediated defense signaling pathway.
B. Elevated reactive oxygen species levels enhance SA-mediated defense signaling.
This statement is correct. Reactive oxygen species (ROS) are produced during stress conditions such as pathogen attack. Elevated ROS levels serve as important signals that enhance salicylic acid (SA)-mediated defense signaling, which plays a key role in the activation of systemic acquired resistance (SAR), a plant defense mechanism against pathogens. ROS can activate various defense genes, including those involved in SA signaling.
C. Under normal (uninfected) conditions, NPR1 is preferentially localized into the nucleus.
This statement is incorrect.NPR1 (Non-expressor of Pathogenesis-Related genes 1) is a key regulator in SA-mediated defense signaling. Under normal, uninfected conditions, NPR1 is actually located in the cytoplasm as an oligomer. Upon SA activation, NPR1 is reduced to a monomer and translocates to the nucleus where it activates defense-related genes. Thus, NPR1 is not localized in the nucleus under uninfected conditions.
D. Gibberellic acid and abscisic acid cannot participate in plant defense signaling.
This statement is incorrect. Gibberellic acid (GA) and abscisic acid (ABA) do participate in plant defense signaling, though their roles are complex and can vary. GA is involved in growth and stress responses, and ABA plays a significant role in regulating stress responses, including drought resistance and pathogen defense. So, GA and ABA can influence defense signaling, though not as prominently as SA or JA.
