Plant Reactive Oxygen Species = Success and Survival

     We’ve spent a good month now in biochemistry learning about Reactive Oxygen Species (ROS). How they originate from the Electron transport chain and are silenced using the Pentose phosphate pathway. We use various antioxidants by NADPH to destroy ROS and prevent cellular damage. But did you know antioxidants are a universal regulator not just in humans and animals? ROS’s also affect plants as well, but instead of being a damaging product, it is used in plants as cell signals for cell growth and proliferation. Plants are adapting to the increased levels of ROS’s that they produce to survive during a global climate crisis.

    Global climate change has been associated with adverse abiotic stress condition including drought, salinity, extreme temperatures, oxygen deprivations, and heavy metals (Hasanuzzaman, M., et al. 2020). These conditions have affected how plants continue to develop and grow which in the broader sense affects global agriculture. Like multicellular organisms’ excess amounts of ROS causes cell damage and apoptosis. However, in plants ROS’s are a fundamental process in employing cell signal information that helps plants adapt to changing environmental conditions. Even though they are beneficial, consequences of excessive ROS accumulation are beginning to destroy equilibrium between antioxidants leading to oxidative stress and cell death.

What we know so far from biochemistry is that GSH is one of the primary antioxidants that we use against ROS. Now here is a list of antioxidant mechanism used by plants: SOD, CAT, APX, GPX, TRX, GRX, GSH, etc. (Hasanuzzaman, M., et al. 2020). Plants will make all these antioxidants in hopes of protecting against too much ROS. But even after these cellular defense mechanisms it isn’t enough to stop cell death. Besides the damaging activity, ROS can act as secondary messengers that signals through a MAPK pathway to increase tolerance against the diverse abiotic stress factors. In fact, what they signal are even more reactive species including reactive sulfur species, reactive carbonyl species, and reactive nitrogen species. In return this signals a positive feedback loop that signals for more cross talk between the species to increase defense against damage. This is fascinating as ROS is a detriment but a benefit in plant biology.

This piece of literature was published last year and stated that this area of research is still relatively unknown. One idea that came to mind when comparing ROS between humans and plants is how can we used ROS to target diseases. We know in cancer ROS is being used by cancer to sustain its own growth and proliferation. But can there be a mechanism that causes the ROS to attack cancer cells and destroy them. It’s a slippery slope because ROS isn’t selective in who it chooses to attack and therefore ROS could just worsen a person condition if treated incorrectly. As Dr. Streifel says metabolism is life and is connected in some way to each and every disease.

 

Hasanuzzaman, M., Bhuyan, M., Zulfiqar, F., Raza, A., Mohsin, S. M., Mahmud, J. A., Fujita, M., & Fotopoulos, V. (2020). Reactive Oxygen Species and Antioxidant Defense in Plants under Abiotic Stress: Revisiting the Crucial Role of a Universal Defense Regulator. Antioxidants (Basel, Switzerland), 9(8), 681. https://doi.org/10.3390/antiox9080681