Correct option is C
Correct Answer: (c)
Explanation: In plant immune responses, plasma membrane NADPH oxidases (RBOHs) are key enzymes responsible for ROS generation. Their activation is tightly regulated and requires calcium binding as well as phosphorylation by calcium-dependent protein kinases (CDPKs). Therefore, the statement claiming that NADPH oxidase activation does not require CDPKs is incorrect. CDPK-mediated phosphorylation is an essential step in RBOH activation during pathogen-triggered immunity.
Information Booster
· ROS production is one of the earliest plant defense responses to pathogen attack.
· Plasma membrane NADPH oxidases (RBOHs) catalyze superoxide generation in the apoplast.
· RBOH proteins contain EF-hand motifs that bind calcium ions.
· CDPKs phosphorylate RBOHs to enhance and sustain ROS production.
· Apoplastic peroxidases also contribute to ROS accumulation during defense responses.
Additional Knowledge
Respiratory burst oxidase homologs (Atrboh genes) encode NADPH oxidases that are functionally similar to those found in animal immune systems. Upon pathogen recognition, calcium influx, CDPK activation, and phosphorylation events converge to regulate ROS bursts. This coordinated control ensures rapid defense signaling while preventing excessive oxidative damage to host tissues.
