PUB - Publikationen an der Universität Bielefeld

Survival under excess light conditions requires the light-induced accumulation of protein LHCSR3 and other photoprotection factors, to enable efficient energy-dependent quenching in the green microalgaChlamydomonas reinhardtii. Here, we demonstrate that the high light-tolerant phenotype of mutanthit1is caused by a de-repression of promoters belonging to photoprotection genes, which in turn results from an inactivation of the E3 ubiquitin ligase substrate adaptor LRS1. Transcriptome analyses ofhit1revealed massive alterations of gene expression modulation as a consequence of perturbed LRS1 function, indicating its role as a crown regulator. In conjunction with random forest-based network modeling, these transcriptome analyses predicted that LRS1 controls photoprotection gene expression via an algal HY5 homolog as its prime transcription factor target. CrHY5 binds to T-box elements present in the promoters of these genes and its inactivation in thehit1mutant via CRISPR-Cas9 genome editing, confirmed the regulatory connection between LRS1 and CrHY5, predicted by the network analysis.