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Cadmium induces ROS-dependent pexophagy in Arabidopsis leaves

Cadmium treatment induces transient peroxisome proliferation in Arabidopsis leaves. To determine whether this process is regulated by pexophagy and to identify the mechanisms involved, we analyzed time course-dependent changes in ATG8, an autophagy marker, as well as the accumulation of peroxisomal marker PEX14a. After 3 h of Cd exposure, the transcript levels of ATG8h, ATG8c, a and i, were slightly up-regulated and then returned to normal. ATG8 protein levels also increased after 3 h of Cd treatment, while an opposite pattern was observed in PEX14. Arabidopsis lines expressing GFP-ATG8a and CFP-SKL enabled us to demonstrate the presence of pexophagic processes in leaves. The Cd-dependent induction of pexophagy was demonstrated by the accumulation of peroxisomes in autophagy (ATG)-related Arabidopsis knockout mutants atg5 and atg7. We show that ATG8a co-localizes with catalase and NBR1 in the electron-dense peroxisomal core, thus suggesting that NBR1 may be an autophagic receptor for peroxisomes, with catalase being possibly involved in targeting pexophagy. Protein carbonylation and peroxisomal redox state suggest that protein oxidation may trigger pexophagy. Cathepsine B, legumain and caspase 6 may also be involved in the regulation of pexophagy. Our results suggest that pexophagy could be an important step in rapid cell responses to cadmium.

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Original Paper:

Calero‐Muñoz, N., Exposito‐Rodriguez, M., Collado‐Arenal, A.M., Rodríguez-Serrano, M., Laureano‐Marín, A.M., Santamaría, M.E., Gotor, C., Díaz, I., Mullineaux, P.M., Romero‐Puertas, M.C., Olmedilla, A., Sandalio, L.M. 2019. Cadmium induces ROS-dependent pexophagy in Arabidopsis leaves. Plant, Cell & Environment. DOI: 10.1111/pce.13597

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