The Cyclic Nucleotide Gated Channels CNGC2 and CNGC4 Support Systemic Wound Responses in Arabidopsis thaliana

Sarah Johns¹Erin Wiegman²Simon Gilroy^2*

• ¹University of Wisconsin-Madison, Madison, Wisconsin, United States
• ²Department of Botany, University of Wisconsin-Madison, Madison, Wisconsin, United States

The local perception of a stimulus such as wounding can trigger plant-wide responses through the propagation of systemic signals that include the vascular transport of diverse chemical messengers, the propagation of electrical changes and even potentially hydraulic waves that rapidly spread throughout the plant body. These systemic signals trigger changes in second messengers such as Ca 2+ that then play roles in triggering subsequent molecular responses.Although the GLUTAMATE RECEPTOR-LIKE (GLR) channels GLR3.3 and GLR3.6 are known to be essential for vascular propagation of wound-induced electrical and Ca 2+ signals, additional channels and/or transporters are likely necessary to further spread responses across the plant. We hypothesized that members of the cyclic nucleotide-gated family of ion channels (CNGCs) might also be involved in the systemic component of this process. Analysis of a library of CNGC mutants for their wound-triggered systemic induction of defense gene expression indicated that CNGC2 and CNGC4 likely participate in both leaf-to-leaf and root-to-leaf systemic spread of wound responses. Mutants in these channels showed wild type-like propagation of Ca 2+ increases from the wound site but then exhibited a limited spread of the Ca 2+wave from the vasculature to other tissues of distal leaves. These results indicate that CNGC2 and CNGC4 likely play roles in spreading the Ca 2+ signal through systemic leaves to help further propagate and amplify the plant-wide wound response. Although CNGC19 has previously been shown to be involved in Ca 2+ signaling at the wound site, knockouts in this gene did not disrupt the long-distance wound response. These observations suggest that the molecular machinery required to triggers the local reaction to damage of the plant is likely distinct from the activities that support systemic spread of the response.