An Arabidopsis plant natriuretic peptide interacts with CATALASE2 to modulate cellular H2O2 homeostasis

Turek IS1,2, Wheeler J3, Gehring C1,4 and Irving HR2

  1. King Abdullah University of Science and Technology, Division of Biological and Environmental Sciences and Engineering, Thuwal, Saudi Arabia.
  2. La Trobe Institute for Molecular Science, La Trobe University, Bendigo, VIC, Australia.
  3. AgriBio, La Trobe University, Bundoora, VIC, Australia.
  4. Department of Chemistry, Biology and Biotechnology, University of Perugia, Perugia, Italy.

Plant natriuretic peptides (PNPs) comprise a novel class of systemically acting peptidic hormones that share some sequence similarity in the active site with their animal analogues regulating salt and water balance. One aspect of understanding the function of these compounds is their potential biotechnological application in conferring increased stress tolerance to plants. Although PNPs modulate many physiological responses, including plant responses to stress, their molecular mode of action still remains unclear. Since H2O2 is a key component of abiotic and biotic stress responses in plants, we set out to investigate if the Arabidopsis thaliana PNP (AtPNP-A) can directly or indirectly affect H2O2 homeostasis. To this end we screened AtPNP-A for interacting partners and identified catalase2 (CAT2), an enzyme capable of H2O2 decomposition, as a candidate direct interactor of AtPNP-A by yeast two-hybrid (Y2H) assay and cross-linking followed by mass spectrometric (MS) analysis. Surface plasmon resonance (SPR) revealed that the biologically active part of AtPNP-A binds specifically to CAT2 in vitro, while a biologically inactive peptide does not. Furthermore, zymograhic analyses revealed that AtPNP-A enhances CAT2 activity in vitro. We also noted that CAT2 activity if lower in homozygous atpnp-a knockdown plants compared with wild type plants. Finally, bimolecular fluorescence complementation (BiFC) revealed that CAT2 interacts with AtPNP-A in chloroplasts, consistent with the organellar localization of the CAT2, and modulates H2O2 levels having implications for plant stress responses.