Hackenberg, Thomas6; Andersen, Trine Juul6; Auzina, Aija6; Gwizdz, Sonia7; Malolepszy, Anna7; Van Der Kelen, Katrien8; Dam, Svend Secher9; Bressendorff, Simon10; Lorentzen, Andrea Maria11; Roepstorff, Peter11; Nielsen, Kåre Lehmann1; Jørgensen, Jan-Elo6; Hofius, Daniel12; Van Breusegem, Frank8; Petersen, Morten10; Andersen, Stig Uggerhøj9
1 Section of Biotechnology, The Faculty of Engineering and Science, Aalborg University, VBN2 EcoDesign, The Faculty of Engineering and Science, Aalborg University, VBN3 Department of Chemistry and Bioscience, The Faculty of Engineering and Science, Aalborg University, VBN4 The Faculty of Engineering and Science, Aalborg University, VBN5 Microbial Communities, The Faculty of Engineering and Science, Aalborg University, VBN6 Molekylærbiologisk Institut7 Department of Molecular Biology and Genetics, Aarhus University8 Department of Plant Biotechnology and Bioinformatics, Ghent University9 Institut for Molekylærbiologi og Genetik - Plante Molekylærbiologi10 Functional genomics11 Institut for Biokemi og Molekylær Biologi12 Biologisk Institut
Programmed cell death often depends on generation of reactive oxygen species, which can be detoxified by antioxidative enzymes, including catalases. We previously isolated catalase-deficient mutants (cat2) in a screen for resistance to hydroxyurea-induced cell death. Here, we identify an Arabidopsis thaliana hydroxyurea-resistant autophagy mutant, atg2, which also shows reduced sensitivity to cell death triggered by the bacterial effector avrRpm1. To test if catalase deficiency likewise affected both hydroxyurea and avrRpm1 sensitivity, we selected mutants with extremely low catalase activities and showed that they carried mutations in a gene that we named NO CATALASE ACTIVITY1 (NCA1). nca1 mutants showed severely reduced activities of all three catalase isoforms in Arabidopsis, and loss of NCA1 function led to strong suppression of RPM1-triggered cell death. Basal and starvation-induced autophagy appeared normal in the nca1 and cat2 mutants. By contrast, autophagic degradation induced by avrRpm1 challenge was compromised, indicating that catalase acted upstream of immunity-triggered autophagy. The direct interaction of catalase with reactive oxygen species could allow catalase to act as a molecular link between reactive oxygen species and the promotion of autophagy-dependent cell death.