Phosphoprotein SAK1 is a regulator of acclimation to singlet oxygen in Chlamydomonas reinhardtii

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Abstract

Singlet oxygen is a highly toxic and inevitable byproduct of oxygenic photosynthesis. The unicellular green alga Chlamydomonas reinhardtii is capable of acclimating specifically to singlet oxygen stress, but the retrograde signaling pathway from the chloroplast to the nucleus mediating this response is unknown. Here we describe a mutant, singlet oxygen acclimation knocked-out 1 (sak1), that lacks the acclimation response to singlet oxygen. Analysis of genome-wide changes in RNA abundance during acclimation to singlet oxygen revealed that SAK1 is a key regulator of the gene expression response during acclimation. The SAK1 gene encodes an uncharacterized protein with a domain conserved among chlorophytes and present in some bZIP transcription factors. The SAK1 protein is located in the cytosol, and it is induced and phosphorylated upon exposure to singlet oxygen, suggesting that it is a critical intermediate component of the retrograde signal transduction pathway leading to singlet oxygen acclimation.

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Setsuko Wakao

University of California, Berkeley, Berkeley, United States

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The authors declare that no competing interests exist.
Brian L Chin

Harvard Medical School, Boston, United States

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The authors declare that no competing interests exist.
Heidi K Ledford

Nature Publishing Group, Cambridge, United States

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The authors declare that no competing interests exist.
Rachel M Dent

University of California, Berkeley, Berkeley, United States

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The authors declare that no competing interests exist.
David Casero

University of California, Los Angeles, Los Angeles, United States

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The authors declare that no competing interests exist.
Matteo Pellegrini

University of California, Los Angeles, Los Angeles, United States

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The authors declare that no competing interests exist.
Sabeeha S Merchant

University of California, Loa Angeles, Los Angeles, United States

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The authors declare that no competing interests exist.
Krishna K Niyogi

University of California, Berkeley, Berkeley, United States

For correspondence
niyogi@berkeley.edu

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The authors declare that no competing interests exist.

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