The earth is warming at the rate of ~32.36 °F every 10 years! We witnessed the devastating effects of a drying climate during the Australian bush fires in January this year. With worsening floods and hurricanes (indicative of climatic imbalances) every year, climate change is not just a problem of the future anymore. Burning fossil fuels results in the production of large amounts of gases such as methane, carbon monoxide, and carbon dioxide. These greenhouse gases do not leave the earth’s atmosphere easily and trap heat thereby raising global temperature. Unsurprisingly, this has caused droughts to nearly double in severity, frequency, and duration.
What does this mean?
Certain cities like Chennai (India) and Cape Town (South Africa) are already experiencing a severe lack of water during summers. Food crops do not tolerate such extreme drought. The loss of productivity due to drought has been about $29 billion between 2005 and 2015. With the world heading towards a population of 10 billion by 2050, scientists need to come up with solutions fast to meet global food demands, especially in the face of increasing water deficit. Thus, we need to find ways to increase drought tolerance in food crops. If adequate measures are not taken and the climate continues to change as rapidly as it is now, we will lose 35% of our current crop yield by 2100.
In order to understand how to improve crop yield during adverse conditions like droughts, we need to look at unique underlying biological mechanisms within plants. Photosynthesis consists of light and dark reactions. The light reaction generates high energy molecules, which need to be used up by subsequent reactions or else they cause photodamage to chloroplast membranes. Additionally, metabolism and CO2 diffusion are severely hindered which directly affects photosynthesis, resulting in reduced crop yield. An essential protein complex in the photosynthesis light reaction is Photosystem II or PSII. The structure and composition of PSII is conserved across evolution from cyanobacteria to more sophisticated plants. PSII has a core protein called D1 which relies on rapid turnover, where the damaged protein is replaced by a new protein during drought stress to continue its photosynthetic function. The absence of proper protein turnover affects crop yields.
Fortunately, there are certain organisms that can enter long-dormant phases during drought by protecting photosynthetic membranes. These may hold the answer to some of our questions.
Can a little-known cyanobacterium hold answers?
Cyanobacteria are aquatic photosynthetic bacteria and the oldest known living fossil. Chloroplasts, little cellular factories that are home to the photosynthesis process, are thought to be derived from ancient cyanobacteria that managed to evolutionarily sneak into plant cells millions of years ago. One special group of cyanobacteria, Nostoc flagelliforme , also known as fat choy, is mainly grown and consumed in China, as a vegetable. This cyanobacterium thrives through states of dehydration and dormancy for long periods of time, sometimes for several years. It desiccates during extreme dry weather but is followed by a complete renewal of photosynthesis upon rehydration. Studies have shown that during dehydration there is little to no membrane damage, like in regular plants. This organism might hold answers to our questions of drought resistance.
Bao-Sheng Qiu’s group in Wuhan, China has been trying to unearth the mechanisms that are important for this bacteria’s impressive capability in functioning under drought conditions. In a study published in Plant Physiology, Qiu’s group has unearthed the molecular mechanisms of drought resistance in N. flagelliforme. They found that certain chaperone proteins interact with each other and play an important role in PSII mediated repair. An essential component of PSII is the heat shock protein family (DnaK and J). Interestingly, Qiu’s study found that both DnaK and J were made in greater amounts under dehydration conditions. It is also fascinating that these proteins interact with enzymes that degrade damaged D1 protein, making them a crucial player in D1 protein turnover. In fact, when these genes were introduced in a freshwater cyanobacterium which was then exposed to dry conditions, the rate of photosynthesis and drought tolerance improved by nearly 25%. The study also discovered new players in this pathway that further simplified the mechanism of drought resistance in N. flagelliforme.
In the above study, deleting the genes that code for heat shock proteins in green algae and higher plants reduced photosynthetic efficiency while overexpressing them increased drought tolerance. It is worth remembering that most of the PSII complexes in N. flagelliforme have similarities with higher plants, making the process of genetic modification a realistic aim. Therefore, a cyanobacterium like N. flagelliforme with its sophisticated mechanism of drought tolerance might hold the key to the imminent challenges of drought and food shortage.
Author:
Ananya Mukherjee did her Ph.D. in Plant Biology at Louisiana State University where she worked on carbon dioxide concentrating mechanism in green algae. She is currently a post-doctoral researcher at the University of Nebraska Lincoln, USA, working on small RNA mechanisms in green algae. She enjoys simplifying science to make it more accessible for everyone. She writes for The Stem times, India bioscience, Research Matters, and many more scicomm platforms. In her free time, she tries to master baking a good sourdough and reading. Follow her on Twitter and Linkedin.
Editors:
Amrita Anand is in her 4th year of Ph.D. in Genetics and Genomics at the Baylor College of Medicine, Houston. She studies the reprogramming potential of certain key factors in the regeneration of mouse inner ear hair cells. She has been actively pursuing Science communication over the last three years as she enjoys bridging the gap between scientists and non-experts. As an editor, she wants to make science more accessible to the public and also hopes the hard work behind the science gets due credit.
Linkedin: https://www.linkedin.com/in/amritaaiyer/
Twitter handle: @_amritanand
Saurja Dasgupta is originally from Kolkata, India. He obtained his Ph.D. at the University of Chicago, where he studied the structure, function, and evolution of catalytic RNA. He is currently doing his postdoctoral research at Massachusetts General Hospital, Boston, where he is trying to understand the biochemical milieu that could have given birth to life on earth (and elsewhere) and reconstruct primitive cells. One of his scientific dreams is to observe the spontaneous emergence of Darwinian evolution in a chemical system. When not thinking about science, Saurja pursues his love for the written word through poetry and song-writing (and meditating on Leonard Cohen’s music). His other passions are trying to make science easier to understand, and fighting unreason and pseudoscientific thinking with a mixture of calm compassion and swashbuckling spirit.
Illustrators:
Disha Chauhan did her Ph.D. in IRBLLEIDA, University of Lleida, Spain in Molecular and Developmental Neurobiology. She has post-doctoral experience in Cell Biology of Neurodegenerative diseases and is actively seeking a challenging research position in academia/industry. Apart from Developmental Neurobiology, she is also interested in Oncology. She is passionate about visual art (Illustration, painting, and photography) and storytelling through it. She enjoys reading, traveling, hiking, and is also dedicated to raising scientific awareness about Cancer. Follow her on Instagram.
Saurabh Gayali recently completed his Ph.D. in Plant Molecular Biology from the National Institute of Plant Genome Research (JNU, New Delhi). Currently, he is DBT RA at IGIB (New Delhi), and his research focuses on finding binding associations of Indian plant metabolites with human pathogen proteins, creating a platform for future plant extract-based drug discovery. He has a keen interest in data analysis, visualization, and database management. He is a skilled 2D/3D designer with a specific interest in scientific illustration. In leisure, Saurabh plays guitar and composes music, does photography, or practices programming. Follow him on Instagram.
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