Nav: Home

Electrons take alternative route to prevent plant stress

June 19, 2019

Plants are susceptible to stress, and with the global impact of climate change and humanity's growing demand for food, it's crucial to understand what causes plant stress and stress tolerance. When plants absorb excess light energy during photosynthesis, reactive oxygen species are produced, potentially causing oxidative stress that damages important structures. Plants can suppress the production of reactive oxygen species by oxidizing P700 (the reaction center chlorophyll in photosystem I). A new study has revealed more about this vital process: the cyclic electron flow induced by P700 oxidation is an electric charge recombination occurring in photosystem I. These findings were published on June 5 in Plants.

The research was led by Professor Chikahiro Miyake, Assistant Professor Shinya Wada, and Kanae Kadota (Kobe University), in collaboration with Professor Amane Makino (Tohoku University) and Associate Professor Yuji Suzuki (Iwate University).

Professor Miyake's team revealed in previous studies that all oxygen-producing photosynthetic species use the P700 oxidation system to deal with oxidative stress. Professor Miyake and Dr Giles Johnson (Senior Lecturer at the University of Manchester) discovered that P700 oxidation is accompanied by a cyclic electron flow (CEF) in photosystem I (PSI). This cyclic flow is not necessary for the linear electron flow that forms part of photosynthesis, so what is it doing? To find out more about this alternative flow, the team analyzed the interaction between the electron carriers linked to the reaction in the PSI complex and the PSII quantum yield [Y(II)] that evaluates the activity levels of the linear electron flow. They used a major crop: wheat leaves.

The results showed that in the electron flow from P700* (excited P700) to ferredoxin (Fd), electron carriers A0, A1, FX, FA/FB are present, and when P700?(oxidized P700) accumulates, a charge recombination occurs in which electrons flow in from the electron carriers (Figure 2). In P700* charge separation occurs, passing electrons to the electron carrier A0 and oxidizing to form P700+. P700+ receives electrons from PSII and is reduced to its ground state. Meanwhile, the electrons accepted by A0 are passed to A1, FX, and FA/FB and flow to NADP+ via Fd, ultimately producing NADPH (chemical energy used in photosynthesis). From observing the reaction speed in leaf samples, the charge recombination between FX and P700+ can be considered the dominant pathway.

The existence of the charge recombination had already been revealed on a cellular level in biochemically isolated PSI complexes, cyanobacteria and green alga. However, until now its role in photosynthesis was unclear. This finding suggests that electrons flow from FX to P700+ based on the reactivity of P700+.

As a secondary result, the team also revealed the mechanism for suppressing the production of reactive oxygen species based on the charge recombination. The electron carriers A0, A1, FX, FA/FB have a very low reduction potential compared to that of oxygen. This suggests that they can easily pass electrons to oxygen and produce reactive oxygen species. The charge recombination revealed in this study plays the role of suppressing the interaction between these electron carriers and oxygen.

This study proposes that the cyclic electron flow induced by P700 oxidation is characterized by a charge recombination reaction that occurs within the PSI complex, including the necessary conditions and the cyclic electron carrier speed. The next step is to investigate the universality of the role of charge recombination within PSI complexes.
-end-


Kobe University

Related Stress Articles:

Red light for stress
Researchers from the Institute of Industrial Science at The University of Tokyo have created a biphasic luminescent material that changes color when exposed to mechanical stress.
How do our cells respond to stress?
Molecular biologists reverse-engineer a complex cellular structure that is associated with neurodegenerative diseases such as ALS
How stress remodels the brain
Stress restructures the brain by halting the production of crucial ion channel proteins, according to research in mice recently published in JNeurosci.
Why stress doesn't always cause depression
Rats susceptible to anhedonia, a core symptom of depression, possess more serotonin neurons after being exposed to chronic stress, but the effect can be reversed through amygdala activation, according to new research in JNeurosci.
How plants handle stress
Plants get stressed too. Drought or too much salt disrupt their physiology.
Stress in the powerhouse of the cell
University of Freiburg researchers discover a new principle -- how cells protect themselves from mitochondrial defects.
Measuring stress around cells
Tissues and organs in the human body are shaped through forces generated by cells, that push and pull, to ''sculpt'' biological structures.
Cellular stress at the movies
For the first time, biological imaging experts have used a custom fluorescence microscope and a novel antibody tagging tool to watch living cells undergoing stress.
Maternal stress at conception linked to children's stress response at age 11
A new study published in the Journal of Developmental Origins of Health and Disease finds that mothers' stress levels at the moment they conceive their children are linked to the way children respond to life challenges at age 11.
A new way to see stress -- using supercomputers
Supercomputer simulations show that at the atomic level, material stress doesn't behave symmetrically.
More Stress News and Stress Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Making Amends
What makes a true apology? What does it mean to make amends for past mistakes? This hour, TED speakers explore how repairing the wrongs of the past is the first step toward healing for the future. Guests include historian and preservationist Brent Leggs, law professor Martha Minow, librarian Dawn Wacek, and playwright V (formerly Eve Ensler).
Now Playing: Science for the People

#566 Is Your Gut Leaking?
This week we're busting the human gut wide open with Dr. Alessio Fasano from the Center for Celiac Research and Treatment at Massachusetts General Hospital. Join host Anika Hazra for our discussion separating fact from fiction on the controversial topic of leaky gut syndrome. We cover everything from what causes a leaky gut to interpreting the results of a gut microbiome test! Related links: Center for Celiac Research and Treatment website and their YouTube channel
Now Playing: Radiolab

The Flag and the Fury
How do you actually make change in the world? For 126 years, Mississippi has had the Confederate battle flag on their state flag, and they were the last state in the nation where that emblem remained "officially" flying.  A few days ago, that flag came down. A few days before that, it coming down would have seemed impossible. We dive into the story behind this de-flagging: a journey involving a clash of histories, designs, families, and even cheerleading. This show is a collaboration with OSM Audio. Kiese Laymon's memoir Heavy is here. And the Hospitality Flag webpage is here.