Systems biology of photosynthetic organisms


Many fundamental systems-level questions about photosynthetic organisms remain unanswered.
What is the full set of genes required for photosynthesis?
Which parts work together? What do all the uncharacterized parts do?

The green alga Chlamydomonas reinhardtii ("Chlamy") is a powerful model photosynthetic organism.
The green plant photosynthetic apparatus is highly conserved and thus can be studied in Chlamy. Chlamy  can grow as a haploid and in the absence of a functional photosynthetic apparatus, allowing rapid isolation of mutants of interest. Its unicellular nature and short doubling time enable higher throughput experiments than alternative systems.

We are developing transformative tools to enable high-throughput studies of gene function in Chlamy.
We developed a new tool, which increases the pace at which mutated genes in Chlamy can be identified by >1,000-fold. We are presently using this tool to develop a genome-wide collection of Chlamy insertion mutants as a powerful resource for the research community (the paper describing the pilot collection can be viewed here).




Molecular mechanisms of efficient photosynthesis


Photosynthetic organisms growing in nearly all environments must cope with rapid fluctuations in light intensity.
The sunlight intensity in most environments can change dramatically in a fraction of a second due to e.g. clouds or leaves moving in the wind. Yet, almost nothing is known about the molecular mechanisms that enable efficient photosynthesis under fluctuating light. We recently discovered that plants have evolved a mechanism that enhances photosynthetic efficiency in changing light environments. We found that this mechanism works by accelerating fluxes of ions across the photosynthetic (thylakoid) membrane.

The Chlamy Carbon Concentrating Mechanism (CCM) allows it to use CO2 much more efficiently than C3 crop plants.
If we understood how this CCM works, we could engineer it into crop plants to increase their growth rates and reduce their need for water and fertilizer. We are working with our collaborators in the NSF project Combining Algal and Plant Photosynthesis to identify and transfer CCM components into the model C3 plant Arabidopsis, as a first step towards ultimately enhancing CO2 uptake in wheat and rice. We recently identified a key protein that we think holds the carbon-fixing enzyme Rubisco in the pyrenoid, the organelle at the heart of the algal CCM.