Workshop: Plants under environmental stress:overcoming current climate change

WORKSHOP DESCRIPTION

The harmful effects of global warming on the environment and human lifestyle are becoming evident during the last few years so that the term “climate emergency” has gained social popularity to describe the environmental risks that humanity is currently facing. Global warming is produced by the anthropogenic increase of emissions of gases such as CO2 and methane, which have greenhouse effect thereby increasing Earth temperature. It is estimated that atmospheric CO2 concentration has almost doubled during the last 150 years since the pre-industrial era due to an economy essentially based on fossil fuels, which has increased global temperature around 1 ºC. Frequent extreme climate episodes including heatwaves, torrential rains, or extended periods of drought, among others, are placing humanity under an unprecedented challenge. A direct approach to address this challenge is the reduction of the use of fossil fuels with the aim of lowering emissions of greenhouse effect gases. However, this implies deep economic, industrial, and cultural changes, which are neither easy nor rapid to implement. Indeed, the Intergovernmental Panel on Climate Change (IPCC) estimates that CO2 must reach net zero emissions by 2050 [1], yet this long period could make some of the negative effects of global warming irreversible. Thus, the approach of lowering emissions of greenhouse effect gases needs to be complemented with strategies to decrease the concentration of CO2 already accumulated in the atmosphere. Current technologies for trapping atmospheric CO2 are inefficient, expensive, and only provide partial and delayed solutions to this complex problem. Current models estimate the need of 2-4 times improvement in the efficiency of carbon capture technologies to obtain significant results from this approach [2]. Therefore, ecosystem-based biotechnological solutions are emerging as a promising possibility. By using sun light energy to fix atmospheric CO2, photosynthesis is the primary source of organic material into the biosphere hence being essential for life on Earth. Thus, strategies to improve photosynthesis efficiency by both terrestrial and aquatic photosynthetic organisms, in combination with the availability of molecular and genetic tools to improve crop acclimation to the stressful environmental conditions triggered by global warming, are promising alternatives to address the current climate crisis [3, 4]. The aim of the workshop “Plants under environmental stress: overcoming current climate challenges”, is to bring together top national and international scientists in the fields of photosynthesis and the biotechnological use of photosynthetic organisms to discuss ecosystem-based strategies to address global warming challenges. In this workshop we will also pay attention to strategies to improve plant responses to environmental stresses affecting crop productivity.

Photosynthesis, a biological process of atmospheric CO2 fixation

The evolution of oxygenic photosynthesis by cyanobacteria, the ancestors of plant and algal chloroplasts, around 3.5 billion years ago, provoked the change of a reducing to an oxidizing atmosphere and triggered the evolution of aerobic metabolism so that life on Earth, as we know it, depends on this process. In brief, oxygenic photosynthesis uses the energy of sun light to impulse the transport of electrons derived from water photolysis through a transport chain formed by complexes of proteins, pigments and other cofactors. The final acceptor of these electrons is ferredoxin (Fdx), which can then transfer them to NADP+ to generate NADPH. The photosynthetic electron transport chain promotes the accumulation of protons at the thylakoid lumen, hence generating an electrochemical proton gradient that drives the synthesis of ATP. Reduced Fdx, NADPH and ATP constitute the sources of metabolically useful energy that supports chloroplast biosynthetic metabolism, notably CO2 fixation to produce sugars by the Calvin-Benson cycle. In addition, water photolysis delivers molecular oxygen to the atmosphere. Nevertheless, the transport of electrons in the presence of oxygen inevitably produces reactive oxygen species (ROS). If over-accumulated, as occurs under stressful environmental conditions, the high reactivity of ROS with proteins, lipids and nucleic acids may cause damage to cell structures and, eventually, cell death. However, ROS have also an important signaling function, which is essential for plant development and acclimation to the environment. Therefore, increasing our current knowledge of ROS production and scavenging, their signaling function and the mechanisms of photoprotection of the photosynthetic machinery provide new approaches for improving photosynthesis efficiency and crop productivity, hence an exciting field of research for addressing current climate challenges.

The impact of global warming on agriculture, and of agriculture on global warming

Since its invention in the Neolithic era, about 10.000 years ago, agriculture is the basis of human nutrition, thus sustaining our survival on Earth. Agriculture provides staple food for animal breeding and is the source of crops such as cereals providing about 60% of the calories for most human populations worldwide. Hence, the deleterious effects of global warming on agriculture are expected to have dramatic effects. However, it is worth considering that agriculture also contributes to global warming in different ways. It is estimated that agricultural activities are responsible of 20-25% of total emissions of greenhouse effect gases, including methane and nitrous oxide in addition to CO2. Nitrogen fertilization, which together with the generation of semi-dwarf cereals, were responsible of the impressive increases of agronomic yields brought about by the green revolution in the 1960s, has also negative effects on global warming. It is estimated that the production of nitrogen fertilizers contributes up to 2% of CO2 emissions, not to mention the deleterious effects caused to different ecosystems by the over-accumulation of nitrate and nitrite. Therefore, improving the understanding of the mechanisms underlying the development and growth of plant roots, and the mechanisms of inorganic nitrogen assimilation by plants and algae, are essential for facilitating new strategies for more efficient nitrogen management, healthier land and aquatic ecosystems, and the generation of plants with better response to different environmental stresses. These goals, which are key challenges that plant science must address towards a more sustainable and efficient agriculture, will be discussed in the workshop.

Biotechnological use of plants and algae

Technologies developed to capture atmospheric CO2 and its storage underground geological formations are still inefficient and provide only a temporal solution to the problem of global warming. Thus, strategies based on biological fixation of CO2, which have the additional advantage of improving the formation of useful organic material, are currently feasible alternatives to address global warming [4]. However, Rubisco, the enzyme that catalyzes biological CO2 fixation, evolved in a low-oxygen atmosphere so that it displays oxygenase in addition to the carboxylase activity, thereby making photosynthetic fixation of CO2 a rather inefficient process in the present high-oxygen atmosphere. Therefore, an important challenge in photosynthesis research is the design of more efficient forms of Rubisco that significantly improve CO2 fixation efficiency. Furthermore, the availability of the genome sequences of the most important crops, the advance in massive analyses such as proteomics and metabolomics, and the improvement of genetic tools, such as gene editing with CRISPR/Cas technologies, allow to design new strategies to improve crop productivity under changing climatic conditions [5]. In this regard, very relevant objectives include the generation of crops overcoming the increase pathogen susceptibility caused by global warming and resistant to abiotic stresses such as drought, salinity, and temperature. Understanding root development and the mechanisms of nitrogen assimilation may lead to better tools for land management with the aim of diminishing the use of nitrogen fertilizers which have the side effect of being highly contaminant. Finally, the contribution of photosynthetic microorganisms (cyanobacteria and algae) to the health of aquatic ecosystems, as well as the use of these organisms to produce biomass and molecules of industrial interest, makes biotechnology-based strategies very attractive to address the challenges of climate change.

IPCC (2022) Climate change 2022: Impacts, adaptation and vulnerability
Schweitzer H et al. (2021) Innovating carbon-capture biotechnologies through ecosystem-inspired solutions. One Earth 4: 49-59
Hirt H et al. (2023) PlantAct! – how to tackle the climate crisis. Trends Plant Sci 28: 537-543
Weigmann K (2019) Fixing carbon. EMBO Rep. 20: e47580
Bailey-Serres J et al. (2019) Genetic strategies for improving crop yields. Nature 575: 109-118