ACA pumps maintain leaf excitability during herbivore onslaught

Area of Science:

• Plant signaling and molecular genetics
• Plant-insect interactions
• Plant physiology

Background:

• Plants generate electrical signals, such as slow wave potentials, in response to damage, facilitating communication.
• The robustness of these electrical signals under severe damage conditions suggests underlying genetic mechanisms for maintaining tissue excitability.
• Group insect attacks pose a significant threat, necessitating efficient plant defense responses.

Purpose of the Study:

• To identify genes responsible for maintaining plant tissue excitability during coordinated insect attacks.
• To investigate the role of P-Type II Ca2+-ATPase genes in electrical signaling and plant defense.
• To understand the mechanisms underlying electrical signaling failure under stress conditions.

Main Methods:

• Mechanical wounding and insect (Spodoptera littoralis) attack assays on wild-type and Arabidopsis thaliana aca10 aca12 mutant plants.
• Electrophysiological recordings to measure leaf-to-leaf electrical signals (slow wave potentials).
• Genetic rescue experiments involving the expression of ACA10 in specific vascular tissues.

Main Results:

• Arabidopsis aca10 aca12 mutants exhibited catastrophic failure of electrical signaling and increased susceptibility to Spodoptera littoralis attack.
• Electrical signaling failure was associated with petiole base deformation, chlorosis, and premature senescence, suggesting vascular dysfunction.
• Expression of ACA10 in phloem companion cells rescued electrical signaling and defense, while expression in xylem contact cells provided partial rescue.
• Prolonged darkness also induced electrical signaling failure in aca10 aca12 mutants, indicating a broader role in stress response.

Conclusions:

• The plant vasculature functions as a capacitor, and ACA10/ACA12 are critical for restoring membrane potentials in vascular cells during energy-depleting stresses.
• Failure to restore vascular cell excitability in aca10 aca12 mutants leads to signaling collapse and increased herbivore damage.
• Non-invasive electrophysiology is a valuable tool for studying early senescence events and plant stress responses.