In the latest episode of JGI’s monthly podcast, Genome Insider, Alison Takemura interviews Setsuko Wakao and Kris Niyogi, biologists at UC Berkeley and in Berkeley Lab’s Molecular Biophysics and Integrated Bioimaging (MBIB) Division. In this 20-minute episode, they discuss their research on a tiny group of algae with insanely gorgeous exterior shells.
Using a forward genetics approach, a team of Biosciences researchers revealed that the enzyme hexokinase (HXK1), which is involved in sugar metabolism in organisms ranging from bacteria to plants to humans, is necessary for the regulation of photosynthesis and metabolism in the green alga Chromochloris zofngiensis. Kris Niyogi, a faculty scientist in Molecular Biophysics and Integrated Bioimaging (MBIB), was senior author on the paper, published in Nature Communications Biology.
The unicellular green alga Chromochloris zofingiensis has the ability to shift metabolic modes from photoautotrophic (synthesizing food using light as energy source) to heterotrophic (obtaining food and energy from exogenous sources) in response to carbon source availability in the light. It also has the capacity—under certain conditions—to produce high amounts of commercially relevant bioproducts: notably, the ketocarotenoid astaxanthin, used in feed, cosmetics, and as a nutraceutical, and triacylglycerol (TAG) biofuel precursors.
Understanding how photosynthesis and metabolism are regulated in algae could, via bioengineering, enable scientists to reroute metabolism toward beneficial bioproducts for energy, food, and human health. To that end, Berkeley Lab Biosciences researchers used C. zofingiensis as a simple algal model system to investigate conserved eukaryotic sugar responses, as well as mechanisms of thylakoid breakdown and biogenesis in chloroplasts.
Using cryo-electron microscopy (cryo-EM), which allows an unprecedented level of resolution, Biosciences researchers compared the structure of photosystem I in the moss Physcomitrella patens with its structure in the small flowering land plant Arabidopsis thaliana, and in the green alga Chlamydomonas reinhardtii. Because moss evolved after algae but before vascular land plants, such comparisons can shed light on how plants evolved to move from the ocean to land.
Krishna Niyogi, a faculty scientist in Molecular Biophysics and Integrated Bioimaging (MBIB) and chair of the Department of Plant and Microbial Biology at UC Berkeley, identified a protein called Photosystem II Subunit S (PsbS) involved in regulating photosynthetic light harvesting and hypothesized that increasing the amount of this protein in a plant might make photosynthesis more efficient. In collaboration with researchers at University of Illinois, Urbana, he put this theory to the test. In field trials, the researchers found that increasing the expression of the gene for PsbS, which is found in all plants, improved crops’ water-use efficiency—the ratio of carbon dioxide entering the plant to water escaping—by 25 percent, without significantly sacrificing photosynthesis or yields. The extra PsbS protein tricks plants into partially closing their stomata, the microscopic pores in the leaf that allow water to escape. The study, published March 6 in Nature Communications, is part of an international research project, Realizing Increased Photosynthetic Efficiency (RIPE), supported in part by the Bill & Melinda Gates Foundation. Read more at UC Berkeley News.