Phosphoprotein SAK1 is a regulator of acclimation to singlet oxygen in Chlamydomonas reinhardtii
Setsuko Wakao,
Brian L Chin,
Heidi K Ledford,
Rachel M Dent,
David Casero,
Matteo Pellegrini,
Sabeeha S Merchant,
Krishna K Niyogi
Affiliations
Setsuko Wakao
Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, United States
Brian L Chin
Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, United States
Heidi K Ledford
Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, United States
Rachel M Dent
Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, United States
David Casero
Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, United States
Matteo Pellegrini
Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, United States; Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, United States
Sabeeha S Merchant
Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, United States; Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, United States
Krishna K Niyogi
Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, United States; Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, United States
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.
