The role of Polycomb Repressive Complex 2 (PRC2) in plant acclimation to ambient light

Sunlight is the primary source of energy for our planet. It provides the energy necessary to drive the chemical reactions involved in photosynthesis in plants. It is the key component that initiates the process and enables the conversion of light energy into chemical energy, which is stored in the form of sugars and other organic molecules. These compounds serve as the foundation for the food chain, as they are consumed by other organisms for energy and growth. Therefore, sunlight is fundamental to the sustenance of life on Earth. However, the connection of light perception and signalling with plant growth under changing environmental conditions is still not fully understood. Epigenetics refers to the study of changes in gene expression or cellular phenotype that do not involve alterations to the underlying DNA sequence. One of most well-known and extensively studied epigenetic mechanisms is histone modification. Polycomb Repressive Complex 2 (PRC2) is an evolutionarily conserved histone methyltransferase complex that catalyses trimethylation of lysine 27 of histone H3 (H3K27me3), which leads to epigenetic gene repression. In Arabidopsis thaliana, it is still not fully known how PRC2 contributes to seedling emergence and greening. In this project, we addressed the impact of PRC2 dysfunction on light signalling, photosynthesis and vegetative growth in Arabidopsis, with focus on seedling establishment and vegetative growth of adult plants. Through this project, we have shown a previously unknown connection between epigenetic gene regulation and light adaptation, which is crucial for plant vegetative growth and biomass production.

To answer the contribution of PRC2 repression to light-related growth, we analysed WT and PRC2 mutant plants cultivated under different light conditions for different periods of time. From the results of physiological and molecular experiments (RNA-seq and ChIP-seq), we found that PRC2 regulates genes involved in light signalling and photosynthesis and contributes to light adaptation. In addition, upon chloroplast damage, PRC2 mutants are defective in chloroplast-to-nucleus signalling. This phenotype was common to young seedlings as well as mature plants, suggesting impairment of biogenic and operational control. Further histone modification and transcriptome profiling revealed specific molecular mechanisms involved in the observed phenotypes. These mechanisms will be the subject of further study.
The obtained results will be incorporated into two manuscripts that are under preparation. We expect to publish a peer-reviewed open-access publication during 2024. The second manuscript is expected to follow after the molecular mechanisms suggested to contribute to the observed phenotypes have been more thoroughly supported. In the course of the project, I presented my results at four international conferences and three workshops at local academic institutions: The Czech Plant Nucleus Workshop 2021, 14-15 September 2021, Olomouc, Czech Republic (talk); Young Researchers Symposium on Plant Photobiology 2022, 9-12 March 2022, Freiburg, Germany (online, poster); 7th European Workshop on Plant Chromatin, 18-20 May 2022, Prague, Czech Republic (poster); Follow-up meeting to the UNA Europa funded Early Career Researcher workshop, 6-7 June 2022, Edinburgh, UK (talk); 21st Symposium of the International Society of Endocytobiology, 19-22 July 2022, Ceske Budejovice, Czech Republic (poster); Kostelecké Inspirování 2022, 28-29 November 2022, Kostelec nad Černými lesy, Czech Republic (poster); Plant Sciences Seminars, 30 March 2023, Biology Centre CAS, České Budějovice, Czech Republic (talk). During 2 years, I presented my work 8 times at regular lab meetings of Iva Mozgová group at the Biology Centre CAS.
Thanks to the MSCA project I was able to join three seminars and improve my leadership skills: EMBO course on How to review a scientific paper; Leadership training for early career researchers (organised by ICT Pro s.r.o.) and EMBO Laboratory Leadership for Group Leaders.

PRC2-mediated repression has been traditionally viewed as a major developmental epigenetic mechanism, ensuring stable but reversible repression of developmental genes. Recently, reports are emerging of PRC2 repressing genes involved in environmental and stress responses. In this project, we showed that PRC2 is involved in modulation of light response during photomorphogenesis and vegetative growth, impacting the ability of plants to adapt to changing environmental conditions. Mechanistically, this work uncovers a new molecular connection between epigenetic regulation of nuclear and organellar gene expression during light response and adaptation. The findings of this project represent an important step towards our understanding of how plants can acclimate and adapt to changing and more challenging environmental conditions that are to be expected, and opens new possibilities for plant improvement to mitigate the impact of climate change in the future. The project contributed to firmly establishing a research line that is bridging fundamental and agricultural research and is likely to be of interest for wide public and breeders.

Periodic Reporting for period 1 - RPAAL (The role of Polycomb Repressive Complex 2 (PRC2) in plant acclimation to ambient light)

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