The unknown unknowns of plant cell biology: identifying the functions of conserved, single-copy genes

Wang et al. examine single-copy, conserved genes of unknown function, with OPENER as proof of concept. Plant Cell https://doi.org/10.1105/tpc.19.00033   

By Wei Wang and Totte Niittylä, Umeå Plant Science Centre, Sweden

 Background: Thale cress or Arabidopsis thaliana was the first sequenced plant species, the genome sequence was published already in 2000. Despite being the most intensively studied plant, the function of about 30% of the proteins encoded by the genome remain unknown. In our work we set out to explore this unknown frontier of plant biology by focusing on the unknown genes that are evolutionarily conserved from green algae to higher plants. We reasoned that the study of these unknown genes would help us to understand fundamental cellular processes.

Question: We wanted to break new ground and identify previously uncharacterized essential plant cell processes.

Findings: We think the concept of identifying evolutionarily conserved single copy genes in Arabidopsis with prominent expression in dividing cells was simple but effective. We focused on one of the mutated genes which showed a very early seed abortion phenotype. We named the gene OPENER (OPNR) because the arrested zygote in the mutants had the shape reminiscent of a bottle opener. The interesting feature of OPNR is that the protein encoded by this gene localizes to both nuclear envelope (NE) and mitochondria. This is quite unusual, we only found a handful of proteins with similar localization in the literature. Identification of OPNR uncovered a completely new line of investigation into a previously uncharacterized essential process occurring in dividing plant cells. This project is a good example of the novel insights that can be gained from investigating the unknown unknowns of cell biology.

Next steps: We discovered that OPNR localizes and also interacts with proteins on NE and mitochondria, now we are working on understanding the function of OPNR in these compartments. The challenge is to define the first direct defects caused by the OPNR mutation.

 Wei Wang, Xueyang Zhang, and Totte Niittylä (2019). OPENER Is a Nuclear Envelope and Mitochondria Localized Protein Required for Cell Cycle Progression in Arabidopsis. DOI: https://doi.org/10.1105/tpc.19.00033

Key words: Arabidopsis, seed, nucleus, mitochondria