TY - JOUR TI - The Mars1 kinase confers photoprotection through signaling in the chloroplast unfolded protein response AU - Perlaza, Karina AU - Toutkoushian, Hannah AU - Boone, Morgane AU - Lam, Mable AU - Iwai, Masakazu AU - Jonikas, Martin C AU - Walter, Peter AU - Ramundo, Silvia A2 - Hardtke, Christian S A2 - Kleine-Vehn, Jürgen A2 - Minagawa, Jun VL - 8 PY - 2019 DA - 2019/10/15 SP - e49577 C1 - eLife 2019;8:e49577 DO - 10.7554/eLife.49577 UR - https://doi.org/10.7554/eLife.49577 AB - In response to proteotoxic stress, chloroplasts communicate with the nuclear gene expression system through a chloroplast unfolded protein response (cpUPR). We isolated Chlamydomonas reinhardtii mutants that disrupt cpUPR signaling and identified a gene encoding a previously uncharacterized cytoplasmic protein kinase, termed Mars1—for mutant affected in chloroplast-to-nucleus retrograde signaling—as the first known component in cpUPR signal transmission. Lack of cpUPR induction in MARS1 mutant cells impaired their ability to cope with chloroplast stress, including exposure to excessive light. Conversely, transgenic activation of cpUPR signaling conferred an advantage to cells undergoing photooxidative stress. Our results indicate that the cpUPR mitigates chloroplast photodamage and that manipulation of this pathway is a potential avenue for engineering photosynthetic organisms with increased tolerance to chloroplast stress. KW - organellar protein homeostasis KW - chloroplast-to-nucleus signaling KW - photoprotection JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -