How Do Plants Adapt to Challenging Environmental Conditions? The Transregional Collaborative Research Center "The Green Hub" Enters Its Third Phase
Fluctuations in light intensity and ambient temperature are the two environmental factors that can change most rapidly. For example, light intensity can change from low energy density to extremely high levels within seconds. Therefore, plants—which, after all, cannot leave their location—must adapt to these new conditions particularly quickly and efficiently, a process also known as “acclimatization.” This process is also becoming increasingly important in the targeted breeding of crop plants, as the rapidly changing climatic conditions are currently having a negative impact on global yields.
Since 2016, the Transregional Collaborative Research Center “The Green Hub” has been investigating how the cell organelle chloroplast is involved in these acclimatization processes. Chloroplasts are the site of photosynthesis in leaf cells, where light energy is used to produce sugars, the primary product of photosynthesis. Therefore, it is chloroplasts in particular—as cellular organelles—that perceive changes in light intensity and ambient temperature and can thereby become stressed. How chloroplasts respond and how they control further processes in other parts of the cell through corresponding signals is the focus of “The Green Hub” projects.
To fully understand the complexity of the corresponding molecular processes, it is necessary to bring together a broad range of experimental and conceptual expertise. For this reason, the entire Collaborative Research Center currently comprises 18 subprojects contributed by Ludwig Maximilian University of Munich, Humboldt University of Berlin, the University of Bielefeld, and at RPTU. At the Kaiserslautern site, a total of seven subprojects (including one central project) are led by Stefanie Müller-Schüssele, Torsten Möhlmann, Timo Mühlhaus, Ekkehard Neuhaus, Michael Schroda, Haim Treves, and David Zimmer. The RPTU’s contribution to the initiative has been substantially enhanced by two strategic appointments made by the Department of Biology at RPTU to the professorships in Molecular Botany (Professor Stefanie Müller-Schüssele) and Plant Metabolism (Professor Haim Treves), as well as the recent integration of Dr. David Zimmer, as their project proposals have uniquely filled existing gaps in the scientific approaches.
Professor Müller-Schüssele is investigating how redox processes in chloroplasts—which lead to a change in the oxidation/reduction ratio of individual proteins—respond to high light intensities. This work is particularly significant because this so-called thiol-switch regulation finely tunes the metabolic activity of chloroplasts, while also contributing to the detoxification of reactive oxygen species and the repair of oxidative damage.
Dr. Torsten Möhlmann is investigating how the synthesis of nucleotides (the ubiquitous form of energy in all cell types) is altered under stress conditions and how this process is, surprisingly, coupled with protein synthesis in chloroplasts. As part of this exciting project, individual enzymes have been found to perform entirely new functions that go far beyond their actual catalytic activity.
In “The Green Hub,” so-called omic technologies are used to generate comparatively massive amounts of data, which are then analyzed for their network characteristics in Professor Timo Mühlhaus’s project. This work enables the development of models of molecular stress responses, as all levels of plant responses—such as gene expression, protein synthesis, protein degradation, metabolic changes, and physiological reactions—can be correlated with one another.
The chloroplast is surrounded by a double membrane and must exchange both metabolites and signals with the rest of the cell through this membrane. The characterization of these transport processes and the corresponding proteins is the focus of the research conducted by Professor Ekkehard Neuhaus’s research group.
Under stress, the complex folding of proteins—which is what enables them to function—is often disrupted, necessitating the initiation of elaborate repair reactions. How this is regulated in chloroplasts, which have an extremely high protein concentration, is the primary focus of Professor Michael Schroda, who is studying this using the model alga Chlamydomonas reinhardii. In the previous funding period, this project yielded, among other things, groundbreaking insights into stress-induced disruption of membrane lipid homeostasis and the corresponding transmission of signals to the cell nucleus.
Algae are often masters of adaptation, such as Chlorella ohadii, which can develop optimally even under extreme light intensities that would kill all higher plants. This alga also exhibits an adaptation to low environmental temperatures, as it, being a desert dweller, must regularly endure low nighttime temperatures followed by high daytime temperatures. Prof. Haim Treves brought this model organism from the Israeli desert to Kaiserslautern and will use a combination of gene expression analyses and metabolic studies to determine which specific adaptive mechanisms in this alga enable its remarkable ability to acclimate.
Without the project led by Dr. David Zimmer, the efficient processing of these massive datasets would be impossible. The modern analytical approaches used by all experimental groups generate vast amounts of data, which are examined in this subproject using modern (bio)Computer Science methods to assess their quality, reproducibility, and robustness. In particular, it is crucial that the data be collected and organized using standardized methods, thereby greatly facilitating both internal and external collaboration as well as subsequent reuse. Without these modern computational approaches, the groups conducting biochemical and physiological research would be unable to interpret many of their datasets appropriately. Thus, this new project ensures that all collected information can be interpreted in the necessary depth and is deposited in public repositories in accordance with the so-called FAIR Principles.
In the central project, led by Professor Ekkehard Neuhaus, findings obtained from model organisms—which have led to improved adaptation to challenging environmental conditions—are being transferred to crop plants. To this end, the oilseed plant Camelina sativa, a relative of native rapeseed, is genetically modified accordingly and cultivated under stress conditions to then draw conclusions about oil yields and oil quality.
Professor Ekkehard Neuhaus (site spokesperson for the Transregio-SFB) says: “We are very pleased that the international review panel has once again confirmed the quality and originality of plant sciences at RPTU. Now we are looking to the future so that, with the substantial funding from the DFG, we can conduct another four years of exciting research.”