B‐GATA factors are required to repress high‐light stress responses in Marchantia polymorpha and Arabidopsis thaliana

GATAs are evolutionarily conserved zinc‐finger transcription factors from eukaryotes. In plants, GATAs can be subdivided into four classes, A–D, based on their DNA‐binding domain, and into further subclasses based on additional protein motifs. B‐GATAs with a so‐called leucine‐leucine‐methionine (LLM)‐domain can already be found in algae. In angiosperms, the B‐GATA family is expanded and can be subdivided in to LLM‐ or HAN‐domain B‐GATAs. Both, the LLM‐ and the HAN‐domain are conserved domains of unknown biochemical function. Interestingly, the B‐GATA family in the liverwort Marchantia polymorpha and the moss Physcomitrium patens is restricted to one and four family members, respectively. And, in contrast to vascular plants, the bryophyte B‐GATAs contain a HAN‐ as well as an LLM‐domain. Here, we characterise mutants of the single B‐GATA from Marchantia polymorpha. We reveal that this mutant has defects in thallus growth and in gemma formation. Transcriptomic studies uncover that the B‐GATA mutant displays a constitutive high‐light (HL) stress response, a phenotype that we then also confirm in mutants of Arabidopsis thaliana LLM‐domain B‐GATAs, suggesting that the B‐GATAs have a protective role towards HL stress. Summary Statement In this study, we uncover a conserved role for B‐GATA transcription factors in the protection of plants from high‐light stress.