What is the problem/issue being addressed?
Accurate control of when and where cells divide is critical to development and tissue patterning in multicellular organisms. In plants, cell division research has focused primarily on universally conserved eukaryotic genes, which have previously been studied yeast and animals. Many plant-specific factors that influence cell division likely remain to be uncovered. Here, we focus on one plant-specific gene, the BSL1 phosphatase, that is critical for cell division in the green alga Chlamydomonas, a simple unicellular representative of the plant kingdom. We extend the results to the role of BSL1 homologs on cell division in Arabidopsis, a reference dicot plant. Our results generate new insight into regulation of plant cell division.
Why is it important for society?
(1) Chlamydomonas is a model system for plant cell biology that can inform studies in other plants, including crops, which are themselves less amenable to experimentation. As one example, mutations in a rice BSL1 phosphatase homolog is responsible for increased grain size. Our study will help uncover the function of BSL1 proteins in plants, which may guide rational breeding strategies toward improved yield.
(2) Microalgae, including Chlamydomonas, are emerging as potential cost-effective production platforms for value-added compounds. Numerous bioactive molecules, most recently the receptor-binding domain of the SARS-CoV-2 virus, have been produced in Chlamydomonas. Moreover, a recent toxicological study concluded that consumption of Chlamydomonas present no health concerns (GRAS designation by the US FDA), making it possible to use its biomass either directly for human nutrition, or for the development of “edible” vaccines and other orally administered therapeutics. In recent years there has been rapid developments of diverse synthetic biology tools, enabling targeted genetic engineering of both the nuclear and chloroplast genomes. However, yield is still limited due, in part, to a lack of understanding of factors that restrict cell growth and division under different culturing conditions. The results from the project may help define biological constraints on microalgal biomass production, an important step towards realization of the biotechnological potential of this diverse group of organisms.
Conclusions of the Action
(i) In Chlamydomonas, the BSL1 phosphatase activity is required for timing of basal body segregation and proper orientation of the mitotic spindle.
(ii) In Arabidopsis, BSL family protein activity is required for maintenance of the root meristem.
(iii) A novel biotin ligase (BioID) variant, in combination with global phosphoproteomic profiling has been used to identify candidate BSL1 substrates.
