Zhang Lab @ Danforth
Research Summary
The Zhang Lab at the Donald Danforth Plant Science Center employs algal genomics, plant spectroscopy, and advanced 3D cryo-imaging to study how photosynthetic organisms respond to high temperatures, with focus on photosynthesis.
Global warming increases the frequency with which photosynthetic organisms are exposed to damaging high temperatures. Heat stress impairs plant growth and reduces crop yield. To engineer crops with higher thermo-tolerance, it is imperative to understand how photosynthetic cells sense and respond to high temperatures.
Photosynthesis uses sunlight energy to make food, and it is essential for agricultural production. However, photosynthesis is one of the most heat sensitive processes in plants. To meet the increasing global food demand for the future, we need to increase agricultural yield by engineering more robust and more efficient photosynthesis that can adapt to high temperatures. To achieve this goal, it is crucial to understand how photosynthesis responds to high temperatures and what factors limit its adaptation.
Although heat responses in land plants have been studied for years, several major questions remain open, especially heat sensing and regulation. Despite some advances in understanding heat responses in land plants, studies of algal heat responses are largely limited. Algae have great potential to produce biofuels, but they frequently experience rapid and large temperature fluctuations in ponds or outdoor bioreactors that can severely impact algal growth and viability.
The eukaryotic, unicellular green alga Chlamydomonas reinhardtii is an excellent model to study how photosynthetic cells respond to high temperatures. A genome-saturating, indexed, mutant library of Chlamydomonas has been generated, facilitating both reverse and forward genetic screens under heat stress. Furthermore, a high-throughput and quantitative barcoding approach has been developed in Chlamydomonas, enabling tracking growth rates of individual mutants in pooled cultures and screening for heat-sensitive mutants at genome-wide scale. Cryo-Volume Electron Microscopy (cryo-vEM) and Cryo-Electron Tomography (cryo-ET) are available in Chlamydomonas to reveal 3D cellular structures, especially chloroplast structures, with nanometer resolution.
By using these advanced tools and systems-wide omics studies in Chlamydomonas, we aim to understand how photosynthetic cells respond to high temperatures and identify a list of genes involved in heat sensing, regulation, and adaptation in photosynthetic cells. Novel genes identified in Chlamydomonas that have orthologs in land plants will be investigated in model plant species (e.g. Arabidopsis thaliana) with ultimate goals to improve crop thermo-tolerance.
Light is essential for photosynthesis, but excess light can damage photosynthesis. The normal growth light in plants can become excess under abiotic stresses, especially under high temperatures or challenging field conditions when photosynthesis is compromised. Besides heat stress, Zhang lab also studies light stress and photoprotection pathways, both of which frequently interact with heat stress in plants under field conditions.
