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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Phenomenal phytoplankton: Scientists uncover cellular process behind   
   oxygen production    
    One out of 10 breaths contains oxygen generated by cellular mechanism in   
   microscopic algae    
      
     Date:   
         May 31, 2023   
     Source:   
         University of California - San Diego   
     Summary:   
         According to new research, the amount of oxygen in one of 10 breaths   
         was made possible thanks to a newly identified cellular mechanism   
         that promotes photosynthesis in marine phytoplankton. The new   
         study identifies how a proton pumping enzyme (known as VHA) aids   
         in global oxygen production and carbon fixation from phytoplankton.   
      
      
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   FULL STORY   
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   Take a deep breath. Now take nine more. According to new research, the   
   amount of oxygen in one of those 10 breaths was made possible thanks to   
   a newly identified cellular mechanism that promotes photosynthesis in   
   marine phytoplankton.   
      
   Described as "groundbreaking" by a team of researchers at UC San Diego's   
   Scripps Institution of Oceanography, this previously unknown process   
   accounts for between 7% to 25% of all the oxygen produced and carbon   
   fixed in the ocean.   
      
   When also considering photosynthesis occuring on land, researchers   
   estimated that this mechanism could be responsible for generating up to   
   12% of the oxygen on the entire planet.   
      
   Scientists have long recognized the significance of phytoplankton -   
   - microscopic organisms that drift in aquatic environments -- due to   
   their ability to photosynthesize. These tiny oceanic algae form the   
   base of the aquatic food web and are estimated to produce around 50%   
   of the oxygen on Earth.   
      
   The new study, published May 31 in the journal Current Biology,   
   identifies how a proton pumping enzyme (known as VHA) aids in global   
   oxygen production and carbon fixation from phytoplankton.   
      
   "This study represents a breakthrough in our understanding of marine   
   phytoplankton," said lead author Daniel Yee, who conducted the research   
   while a PhD student at Scripps Oceanography and currently serves as   
   a joint postdoctoral researcher at the European Molecular Biology   
   Laboratory and University of Grenoble Alpes in France. "Over millions   
   of years of evolution, these small cells in the ocean carry out minute   
   chemical reactions, in particular to produce this mechanism that enhances   
   photosynthesis, that shaped the trajectory of life on this planet."   
   Working closely with Scripps physiologist Marti'n Tresguerres, one of   
   his co- advisors, and other collaborators at Scripps and the Lawrence   
   Livermore National Laboratory, Yee unraveled the complex inner workings   
   of a specific group of phytoplankton known as diatoms, which are   
   single-celled algae famous for their ornamental cell walls made of silica.   
      
   Understanding the "proton pump" enzyme Previous research in the   
   Tresguerres Lab has worked to identify how VHA is used by a variety of   
   organisms in processes critical to life in the oceans. This enzyme is   
   found in nearly all forms of life, from humans to single-celled algae, and   
   its basic role is to modify the pH level of the surrounding environment.   
      
   "We imagine proteins as Lego blocks," explained Tresguerres, a study   
   co-author.   
      
   "The proteins always do the same thing, but depending on what other   
   proteins they are paired with, they can achieve a vastly different   
   function."  In humans, the enzyme aids kidneys in regulating blood and   
   urine functions.   
      
   Giant clams use the enzyme to dissolve coral reefs, where they secrete an   
   acid that bores holes in the reef to take shelter. Corals use the enzyme   
   to promote photosynthesis by their symbiotic algae, while deep-sea worms   
   known as Osedax use it to dissolve the bones of marine mammals, such   
   as whales, so they can consume them. The enzyme is also present in the   
   gills of sharks and rays, where it is part of a mechanism that regulates   
   blood chemistry. And in fish eyes, the proton pump helps deliver oxygen   
   that enhances vision.   
      
   Looking at this previous research, Yee wondered how the VHA enzyme   
   was being used in phytoplankton. He set out to answer this question   
   by combining high- tech microscopy techniques in the Tresguerres Lab   
   and genetic tools developed in the lab of the late Scripps scientist   
   Mark Hildebrand, who was a leading expert on diatoms and one of Yee's   
   co-advisors.   
      
   Using these tools, he was able to label the proton pump with a fluorescent   
   green tag and precisely locate it around chloroplasts, which are known   
   as "organelles" or specialized structures within diatom cells. The   
   chloroplasts of diatoms are surrounded by an additional membrane compared   
   to other algae, enveloping the space where carbon dioxide and light   
   energy are converted into organic compounds and released as oxygen.   
      
   "We were able to generate these images that are showing the protein   
   of interest and where it is inside of a cell with many membranes," said   
   Yee. "In combination with detailed experiments to quantify photosynthesis,   
   we found that this protein is actually promoting photosynthesis by   
   delivering more carbon dioxide, which is what the chloroplast uses to   
   produce more complex carbon molecules, like sugars, while also producing   
   more oxygen as a by-product."  Connection to evolution Once the underlying   
   mechanism was established, the team was able to connect it to multiple   
   aspects of evolution. Diatoms were derived from a symbiotic event between   
   a protozoan and an algae around 250 million years ago that culminated into   
   the fusing of the two organisms into one, known as symbiogenesis. The   
   authors highlight that the process of one cell consuming another, known   
   as phagocytosis, is widespread in nature. Phagocytosis relies on the   
   proton pump to digest the cell that acts as the food source. However,   
   in the case of diatoms, something special occurred in which the cell   
   that was eaten didn't get fully digested.   
      
   "Instead of one cell digesting the other, the acidification driven by   
   the proton pump of the predator ended up promoting photosynthesis by   
   the ingested prey," said Tresguerres. "Over evolutionary time, these   
   two separate organisms fused into one, for what we now call diatoms."   
   Not all algae have this mechanism, so the authors think that this proton   
   pump has given diatoms an advantage in photosynthesis. They also note that   
   when diatoms originated 250 million years ago, there was a big increase   
   in oxygen in the atmosphere, and the newly discovered mechanism in algae   
   might have played a role in that.   
      
   The majority of fossil fuels extracted from the ground are believed   
   to have originated from the transformation of biomass that sank to   
   the ocean floor, including diatoms, over millions of years, resulting   
   in the formation of oil reserves. The researchers are hopeful that   
   their study can provide inspiration for biotechnological approaches   
   to improve photosynthesis, carbon sequestration, and biodiesel   
   production. Additionally, they think it will contribute to a better   
   understanding of global biogeochemical cycles, ecological interactions,   
   and the impacts of environmental fluctuations, such as climate change.   
      
   "This is one of the most exciting studies in the field of symbiosis   
   in the past decades and it will have a large impact on future research   
   worldwide," said Tresguerres.   
      
   Additional co-authors include Raffaela Abbriano, Bethany Shimasaki,   
   Maria Vernet, Greg Mitchell, and the late Mark Hildebrand of Scripps   
   Oceanography; Ty Samo, Xavier Mayali, and Peter Weber of the Lawrence   
   Livermore National Laboratory; and Johan Decelle of University of   
   Grenoble Alpes.   
      
   The authors did not receive any funding for this study. Yee's doctoral   
   studies at Scripps Oceanography were supported by the Scripps Fellowship,   
   the NIH training grant, and the Ralph Lewin Graduate Fellowship. Funds by   
   UC San Diego's Arthur M. and Kate E. Tode Research Endowment in Marine   
   Biological Sciences supported the purchase of a microscope that was   
   essential for the research.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Marine_Biology # Botany # Sea_Life # Biology   
             o Earth_&_Climate   
                   # Global_Warming # Oceanography # Environmental_Awareness   
                   # Ecology   
       * RELATED_TERMS   
             o Phytoplankton o Dead_zone_(ecology) o Carbon_dioxide o   
             Plankton o Plant o Oxygen o Breath o Algal_bloom   
      
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   Story Source: Materials provided by   
   University_of_California_-_San_Diego. Original written by Brittany   
   Hook. Note: Content may be edited for style and length.   
      
      
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   Journal Reference:   
      1. Daniel P. Yee et al. Report|Online Now PDF Figures Save Reprints   
      Request   
         The V-type ATPase enhances photosynthesis in marine phytoplankton   
         and further links phagocytosis to symbiogenesis. Current Biology,   
         2023 DOI: 10.1016/j.cub.2023.05.020   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230531150117.htm   
      
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