b'12 Carnegie Science|Fall 2019How Plant Cells Neutralize Self-harmPhotosynthesis makes our atmosphere oxygen-rich and forms the bedrock of our food supply. But under changing or stressful environmental conditions, the photosynthetic process can become unbalanced, resulting in an excess of highly reactive oxygen molecules that could cause cellular damage if they arent neutralized. Understanding how plants minimize this self-inflicted harm could help scientists engineer crops with improved yields and fight Carnegie postdoctoral associate Shai Saroussi (left) and hunger in a changing climate. staff scientist Arthur Grossman (right) led the study.New work in Proceedings of theImages courtesy Carnegie Institution for ScienceNational Academy of Sciences led by Carnegies Shai Saroussi and Arthurstage of operations slows down or evenThe former they describe as a clutch Grossman explores how theshuts off altogether, which could lead to athat helps the sugar-manufacturing part photosynthetic algae Chlamydomonasbuild-up of highly reactive oxygenof the photosynthetic apparatus get up to shields itself from this danger.byproducts when the light returns.speed again after the surrounding Photosynthesis takes place inWhen the battery isnt charging, theconditions change from darkness to light. stages. First, light is absorbed and usedcells need to divert this reactivity intoThe latter they describe as a release valve to produce energy molecules, whichother processes that minimize theon a pressure cooker, diverting a then power the second stage in whichpossibility of cellular damage, Grossmandangerous build-up of reactive byproducts carbon dioxide from the air is fixed intoadded.after an environmentally caused sugars, such as glucose and sucrose.The research teamwhich alsoproduction slowdown. One aspect of the researchersincluded Devin Karns, Dylan Thomas, andIt is amazing to see how the cells work demonstrates that starchMatthew Posewitz of the Colorado Schoolorchestrate these machineries to optimize synthesis is an important metabolicof Mines, as well as Clayton Bloszies andphotosynthesis and minimize cellular pathway that drives photosynthesis.Oliver Fiehn of the University ofdamage, Saroussi concluded. Our Think of the sugar- and starch- California-Davisfocused onfindings show a piece of the puzzle of how manufacturing process as charging aunderstanding the functions of twophotosynthetic organisms have evolved to plants battery with energy that it canproteins called FLV and PTOX, whichmanage their energy budgets in a use later, Grossman explained. protect plant cells by facilitating thechanging environment.But under stressful conditions, orconversion of the reactive oxygen in the absence of light, the secondproducts into water.Photosynthesis is the process that plants andSUPPORT:some other organisms use to convert sunlight,The U.S. Department of Energy, the U.S. National Institutes of carbon dioxide, and water into sugars for foodHealth, the Carnegie Institution for Science, and the Colorado and oxygen as a byproduct. School of Mines supported this work. Image courtesy Brookhaven National Laboratory'