Hackenberg, Thomas3; Juul, Trine4; Auzina, Aija3; Gwizdz, Sonia4; Malolepszy, Anna3; Van Der Kelen, Katrien5; Dam, Svend4; Bressendorff, Simon9; Lorentzen, Andrea Maria7; Roepstorff, Peter7; Nielsen, Kare Lehmann10; Jorgensen, Jan-Elo4; Hofius, Daniel11; Van Breusegem, Frank5; Petersen, Morten12; Andersen, Stig Uggerhoj4
1 Functional Genomics, Department of Biology, Faculty of Science, Københavns Universitet2 Department of Biology, Faculty of Science, Københavns Universitet3 Molekylærbiologisk Institut4 Aarhus University5 Ghent University6 Computational and RNA Biology, Department of Biology, Faculty of Science, Københavns Universitet7 Institut for Biokemi og Molekylær Biologi8 Aalborg University9 Computational and RNA Biology, Department of Biology, Faculty of Science, Københavns Universitet10 Aalborg University11 Department of Biology, Faculty of Science, Københavns Universitet12 Functional Genomics, Department of Biology, Faculty of Science, Københavns Universitet
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.