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Electrogenic proton pumps have been implicated in the generation of slow wave potentials (SWPs), damage-induced membrane depolarizations that activate the jasmonate (JA) defense pathway in leaves distal to wounds. However, no defined H+-ATPases have been shown to modulate these electrical signals. Pilot experiments revealed that the proton pump activator fusicoccin attenuated SWP duration in Arabidopsis. Using mutant analyses, we identified Arabidopsis H+-ATPase 1 (AHA1) as a SWP regulator. The duration of the repolarization phase was strongly extended in reduced function aha1 mutants. Moreover, the duration of SWP repolarization was shortened in the presence of a gain-of-function AHA1 allele. We employed aphid electrodes to probe the effects of the aha1 mutation on wound-stimulated electrical activity in the phloem. Relative to the wild type, the aha1-7 mutant increased the duration and reduced the amplitudes of electrical signals in sieve tube cells. In addition to affecting electrical signaling, expression of the JA pathway marker gene JAZ10 in leaves distal to wounds was enhanced in aha1-7. Consistent with this, levels of wound-response jasmonoyl-isoleucine were enhanced in the mutant, as was defense against a lepidopteran herbivore. The work identifies a discrete member of the P-type ATPase superfamily with a role in leaf-to-leaf electrical signaling and plant defense.

Cellular studies of filamentous actin (F‐actin) processes commonly utilize fluorescent versions of toxins, peptides, and proteins that bind actin. While the choice of these markers has been largely based on availability and ease, there is a severe dearth of structural data for an informed judgment in employing suitable F‐actin markers for a particular requirement. Here, we describe the electron cryomicroscopy structures of phalloidin, lifeAct, and utrophin bound to F‐actin, providing a comprehensive high‐resolution structural comparison of widely used actin markers and their influence towards F‐actin. Our results show that phalloidin binding does not induce specific conformational change and lifeAct specifically recognizes closed D‐loop conformation, i.e., ADP ‐Pi or ADP states of F‐actin. The structural models aided designing of minimal utrophin and a shorter lifeAct, which can be utilized as F‐actin marker. Together, our study provides a structural perspective, where the binding sites of utrophin and lifeAct overlap with majority of actin‐binding proteins and thus offering an invaluable resource for researchers in choosing appropriate actin markers and generating new marker variants.

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