Using the SLAC National Accelerator Laboratory’s Linac Coherent Light Source (LCLS) X-ray laser, an international collaboration led by scientists at Berkeley Lab and SLAC captured the all four stable oxidation states of photosystem II— plus two transitional states—at natural temperature and the highest resolution to date.
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.
When plants absorb more light energy than they can use—such as during a brief period of intense illumination—they have mechanisms to dissipate the excess energy as heat, thereby avoiding damage to their light-harvesting pigment complexes. Research has suggested that engineering plants’ photoprotection capabilities to minimize productivity loss could increase crop yields by up to 30 percent. And that would go a long way toward meeting future global food demand. However, significant gaps remain in scientists’ understanding of the molecular details underlying these mechanisms, including how they are triggered and their activation dynamics. Now, work by Berkeley Lab scientists, reported in pair of recent papers, provides several key insights into the mechanisms underlying one type of photoprotection.
Karen Davies, a staff scientist in the Molecular Biophysics and Integrated Bioimaging (MBIB) Division, is one of six Berkeley Lab scientists selected by the U.S. Department of Energy’s Office of Science to receive significant funding through its Early Career Research Program. The scientists are each expected to receive grants of up to $2.5 million over five years to cover year-round salary plus research expenses. Davies’ focus is on protein structure and bioenergetics, which includes the study of the flow of energy in living organisms. Her award is for “Structure of the Cyanobacterial NAD(P)H Dehydrogenase Complex (NDH-1) and Its Role in Cyclic Electron Flow and Carbon Dioxide Hydration,” selected by the Office of Basic Energy Sciences.
“The key design principle of natural photosynthesis is the closing of the photosynthetic cycle on the shortest possible length scale under membrane separation of the incompatible water oxidation and proton reduction environments,” said Heinz Frei, a senior scientist in Biosciences’ Molecular Biophysics and Integrated Bioimaging (MBIB) Division. With collaborators Eran Edri, a former postdoctoral fellow in MBIB now at Ben-Gurion University, and Shaul Aloni in the Molecular Foundry Division, Frei developed a fabrication method to make a square-inch sized artificial photosystem, in the form of an inorganic core-shell nanotube array, that implements this design principle for the first time. The method was described in a paper published earlier this year in ACS Nano.