The mitochondrial outer membrane AAA ATPase AtOM66 affects cell death and pathogen resistance in Arabidopsis thaliana

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  • Zhang et al, 2014, The mitochondrial outer membrane

    Rights statement: This is the peer reviewed version of the following article: Zhang, B., Van Aken, O., Thatcher, L., De Clercq, I., Duncan, O., Law, S., ... Whelan, J. (2014). The mitochondrial outer membrane AAA ATPase AtOM66 affects cell death and pathogen resistance in Arabidopsis thaliana. The Plant Journal, 80(4), 709-727. 10.1111/tpj.12665, which has been published in final form at http://dx.doi.org/10.1111/tpj.12665. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

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Abstract

One of the most stress-responsive genes encoding a mitochondrial protein in Arabidopsis (At3g50930) has been annotated as AtBCS1 (cytochrome bc1 synthase 1), but was previously functionally uncharacterised. Here, we show that the protein encoded by At3g50930 is present as a homo-multimeric protein complex on the outer mitochondrial membrane and lacks the BCS1 domain present in yeast and mammalian BCS1 proteins, with the sequence similarity restricted to the AAA ATPase domain. Thus we propose to re-annotate this protein as AtOM66 (Outer Mitochondrial membrane protein of 66 kDa). While transgenic plants with reduced AtOM66 expression appear to be phenotypically normal, AtOM66 over-expression lines have a distinct phenotype, showing strong leaf curling and reduced starch content. Analysis of mitochondrial protein content demonstrated no detectable changes in mitochondrial respiratory complex protein abundance. Consistent with the stress inducible expression pattern, over-expression lines of AtOM66 are more tolerant to drought stress but undergo stress-induced senescence earlier than wild type. Genome-wide expression analysis revealed a constitutive induction of salicylic acid-related (SA) pathogen defence and cell death genes in over-expression lines. Conversely, expression of SA marker gene PR-1 was reduced in atom66 plants, while jasmonic acid response genes PDF1.2 and VSP2 have increased transcript abundance. In agreement with the expression profile, AtOM66 over-expression plants show increased SA content, accelerated cell death rates and are more tolerant to the biotrophic pathogen Pseudomonas syringae, but more susceptible to the necrotrophic fungus Botrytis cinerea. In conclusion, our results demonstrate a role for AtOM66 in cell death and amplifying SA signalling.
Peer-reviewedYes
Original languageEnglish
Pages (from-to)709-727
Number of pages19
JournalThe Plant Journal
Volume80
Issue number4
DOIs
StatePublished - 27 Oct 2014

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