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Journal Articles Plant Journal Year : 2020

Endoplasmic reticulum‐mediated unfolded protein response is an integral part of singlet oxygen signalling in plants

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Abstract

Singlet oxygen ($^1$O$_2$) is a by-product of photosynthesis that triggers a signalling pathway leading to stress acclimation or to cell death. By analyzing gene expressions in a $^1$O$_2^-$overproducing Arabidopsis mutant ($ch$1) under different light regimes, we show here that the $^1$O$_2$ signalling pathway involves the endoplasmic reticulum (ER)-mediated unfolded protein response (UPR). $ch$1 plants in low light exhibited a moderate activation of UPR genes, in particular $bZIP60$, and low concentrations of the UPR-inducer tunicamycin enhanced tolerance to photooxidative stress, together suggesting a role for UPR in plant acclimation to low $^1$O$_2$ levels. Exposure of ch1 to high light stress ultimately leading to cell death resulted in a marked upregulation of the two UPR branches ($bZIP60/IRE1$ and $bZIP28/bZIP17$). Accordingly, mutational suppression of $bZIP60$ and $bZIP28$ increased plant phototolerance, and a strong UPR activation by high tunicamycin concentrations promoted high light-induced cell death. Conversely, light acclimation of $ch$1 to $^1$O$_2$ stress put a limitation in the high light-induced expression of UPR genes, except for the gene encoding the BIP3 chaperone, which was selectively upregulated. $BIP3$ deletion enhanced Arabidopsis photosensitivity while plants treated with a chemical chaperone exhibited enhanced phototolerance. In conclusion, $^1$O$_2$ induces the ER-mediated UPR response that fulfils a dual role in high light stress: a moderate UPR, with selective induction of $BIP3$, is part of the acclimatory response to $^1$O$_2$, and a strong activation of the whole UPR is associated with cell death.
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Dates and versions

hal-03303919 , version 1 (28-07-2021)

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Inès Beaugelin, Anne Chevalier, Stefano d'Alessandro, Brigitte Ksas, Michel Havaux. Endoplasmic reticulum‐mediated unfolded protein response is an integral part of singlet oxygen signalling in plants. Plant Journal, 2020, 102 (6), pp.1266-1280. ⟨10.1111/tpj.14700⟩. ⟨hal-03303919⟩
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