JBC 297, 101424 When grown under regular, “white” light conditions– that is, visible light, which varies from violet light with a wavelength of about 400 nm to red at 700 nm– cyanobacteria harvest that light using generally chlorophyll a, which takes in light with wavelengths as much as a maximum of about 700 nm. When grown in far-red light (up to about 800 nm), some terrestrial cyanobacteria convert a portion of that chlorophyll a into chlorophylls d and f, which absorb longer wavelengths of light. These alternative kinds of chlorophyll provide such organisms the ability to collect far-red light and use it efficiently for photosynthesis, which permits those cyanobacteria to flourish in low- or filtered-light environments, such as takes place under trees or plants.
” We knew from separating and identifying the complexes that photosystem I includes 7 to 8 chlorophyll f molecules, and that photosystem II consists of one chlorophyll d particle and 4 to 5 chlorophyll f particles, along with about 90 percent of the initial chlorophyll a, so we wished to know where those changes happened in the complexes,” stated Bryant. “One way to figure that out is to figure out the structure of the complexes, but due to the fact that they are complicated and so big– and the chemical distinctions are so small– it was very difficult.” The photosystem I and II complexes are extremely tough to crystallize– because they are huge, membrane-bound complexes– so X-ray crystallography, a basic laboratory method for determining the three-dimensional structures of molecules, was not likely to work. The researchers then relied on cryo-EM, but the small distinctions between the forms of chlorophyll molecules extended the limitations of cryo-EM resolution to detect. The chlorophylls differ at just a couple of atoms of comparable mass.
” My collaborator, Chris Gisriel, who is a postdoctoral fellow in Gary Brudvigs lab at Yale, was lucky to achieve an extremely high-resolution structure for the photosystem II complex– 2.25 angstrom (Å)– enabling him to envision the distinctions in some of the chlorophylls directly,” said Bryant. In a complex like photosystem I that includes almost 100 pigment particles and 11 protein subunits or photosystem II with 35 chlorophylls and 20 protein subunits, these little changes are like looking for a couple of needles 2 extremely big haystacks. By applying this technique and others to the structures figured out using cryo-EM, they were able to determine the locations of chlorophyll f molecules in the two photosystem complexes and the position of the single chlorophyll d particle in photosystem II.
” Identifying the structural basis for how this far-red light-absorption happens in nature is a crucial action forward,” said Gisriel, first author of both research studies. “The recognition of the accurate places in the photosystem I and II complexes where the alternate types of chlorophyll are incorporated could open the doors for amazing future applications. Crops could possibly be crafted to harvest light beyond the noticeable spectrum. In addition, 2 crops could potentially be grown together, with shorter crops, using the filtered far-red light from their shaded places beneath taller crops. Alternatively, plants could be grown more detailed together because of better light capture in the leaves underneath the canopy.” In addition to Bryant and Gisriel, the research study team for the very first paper, titled “Structure of a photosystem I-ferredoxin complex from a marine cyanobacterium offers insights into far-red light photoacclimation,” includes, David A. Flesher, Gaozhong Shen, Jimin Wang, Ming-Yang Ho, and Gary W. Brudvig. Financing was provided by the U.S. National Science Foundation and the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences.
The research team for the 2nd paper, entitled “Structure of a monomeric photosystem II core complex from a cyanobacterium adjusted to far-red light exposes the functions of chlorophylls d and f,” includes Gaozhong Shen, Ming-Yang Ho, Vasily Kurashov, David A. Flesher, Jimin Wang, William H. Armstrong, John H. Golbeck, M.R. Gunner, David J. Vinyard, Richard J. Debus, and Gary W. Brudvig. The research study was supported by the U.S. National Science Foundation, the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, the U.S. Department of Energy, Division of Chemical Sciences, Geosciences, and Biosciences, Photosynthesis Systems, and the National Institute of General Medical Sciences of the U.S. National Institutes of Health.
Recommendations:” Structure of a photosystem I-ferredoxin complex from a marine cyanobacterium provides insights into far-red light photoacclimation” by Christopher J. Gisriel, David A. Flesher, Gaozhong Shen, Jimin Wang, Ming-Yang Ho, Gary W. Brudvig and Donald A. Bryant, January 2022, Journal of Biological Chemistry.DOI: 10.1016/ j.jbc.2021.101408.
” Structure of a monomeric photosystem II core complex from a cyanobacterium adjusted to far-red light reveals the functions of chlorophylls d and f” by Christopher J. Gisriel, Gaozhong Shen, Ming-Yang Ho, Vasily Kurashov, David A. Flesher, Jimin Wang, William H. Armstrong, John H. Golbeck, Marilyn R. Gunner, David J. Vinyard, Richard J. Debus, Gary W. Brudvig and Donald A. Bryant, January 2022, Journal of Biological Chemistry.DOI: 10.1016/ j.jbc.2021.101424.
Cyanobacteria are bacteria that get energy through oxygen-producing photosynthesis and are discovered nearly everywhere, consisting of extreme environments like hot-springs, deserts, and polar regions. They are among the earliest organisms in the world, and their capability to produce oxygen through photosynthesis is believed to have been very important to changes in the early Earths atmosphere that led the way for the development of varied and complex life forms. They are likewise essential model organisms, with possible applications for bioethanol production, as dietary supplements, and as food colorings.
Structures of photosystem I (right) and photosystem II (left) from cyanobacterial cells grown in far-red light. 2 brand-new research studies recognized the areas of changes in these complexes that enable the cyanobacteria to utilize far-red light for photosynthesis. When grown in far-red light, cells replace numerous particles of chlorophyll a with chlorophyll f (pink radiance) in the photosystem complexes and a single chlorophyll a is replaced with chlorophyll d in photosystem II (red radiance). This single chlorophyll d particle is the functional center of photosystem II and is the website where light sets off the electron transfer that initiates the process of water oxidation to produce oxygen. Credit: Girsiel, et al. JBC 297, 101408 and Gisriel, et al.
Considering that the energy available in far-red light is equivalent to 15% of overall solar radiation reaching Earth, this capability provides these organisms a benefit in completing with plants and other cyanobacteria for light for photosynthesis.
“But it turns out that if you put them in far-red light, some cyanobacteria activate a set of about 20 genes that permit them to customize their photosynthetic apparatus and the chlorophylls that they produce so that they can use far-red light for photosynthesis. When grown in far-red light, cells replace several molecules of chlorophyll a with chlorophyll f (pink radiance) in the photosystem complexes and a single chlorophyll a is changed with chlorophyll d in photosystem II (red radiance). When grown under normal, “white” light conditions– that is, noticeable light, which ranges from violet light with a wavelength of about 400 nm to red at 700 nm– cyanobacteria harvest that light utilizing primarily chlorophyll a, which soaks up light with wavelengths up to an optimum of about 700 nm. When grown in far-red light (up to about 800 nm), some terrestrial cyanobacteria convert a portion of that chlorophyll a into chlorophylls d and f, which take in longer wavelengths of light.
When cyanobacteria reside in low-light conditions, such as below a pond surface or under a plant canopy on a forest floor, some have the ability to change from utilizing the noticeable light that is most conducive to their development and photosynthetic activities to gathering the weaker, far-red sunlight that filters to them. The present research study provides the structural basis for the ability of such cyanobacteria to use far-red light for oxygen-evolving photosynthesis. Credit: Shireen Dooling, Biodesign Institute at Arizona State University
These alternates are attuned to longer wavelengths, which permits the cyanobacteria to effectively utilize far-red light to carry out oxygen-evolving photosynthesis. Thinking about that the energy available in far-red light is comparable to 15% of overall solar radiation reaching Earth, this ability provides these organisms an advantage in competing with plants and other cyanobacteria for light for photosynthesis.
The structures are described in two documents appearing online in the Journal of Biological Chemistry and could ultimately help researchers engineer crop plants that can utilize a more comprehensive wavelength spectrum of light for growth.
” If you would have asked me 10 years ago if you might grow most cyanobacteria in far-red light, I would have chuckled,” said Donald A. Bryant, Ernest C. Pollard Professor in Biotechnology and Professor of Biochemistry and Molecular Biology at Penn State and the leader of the research team. “But it ends up that if you put them in far-red light, some cyanobacteria activate a set of about 20 genes that permit them to modify their photosynthetic apparatus and the chlorophylls that they produce so that they can use far-red light for photosynthesis. Because making that discovery in 2013, we have been attempting to understand how that works.”
