From Alcohol to Aldehyde: Characterization of Monolignol Oxidoreductases in Arabidopsis thaliana and Their Possible Involvement in the Extracellular Phenolics Pool

The Berberine bridge enzyme-like (BBE-like) protein family are flavoproteins that are present in bacteria, fungi and plants. In Arabidopsis thaliana, seven subgroups have been identified with a total of 27 genes encoding BBE-like enzymes (AtBBE-like). AtBBE-like proteins are involved in stress-induced plant responses as well as developmental processes. Our work focusses on AtBBE-like subgroup six, from which two members have been found to oxidize monolignols. We therefore hypothesize an involvement of AtBBE-like enzymes in the regulation of the extracellular monolignol pool in planta.
In order to unravel spatiotemporal expression patterns of the five genes from AtBBE-like subgroup 6 on the tissue level, we generated transcriptional reporter lines and found expression in roots, where the individual genes show different expression patterns on the tissue level. Additionally, AtBBE-like 15, 24 and 26 reporter lines show expression during flower development. For all genes from subgroup 6, qRT-PCR revealed high levels of expression in roots. Phenotyping of T-DNA insertion lines do not exhibit an obvious phenotype.
Further phenotypic characterization of loss-of-function mutants generated with CRISPR/Cas9, detailed description of reporter lines and generation of fluorescent reporter lines will widen our understanding of subgroup six of the AtBBE-like protein family.