Exploring the molecular mechanisms that allow plants to control their development and adapt to environmental changes
Imagine if every cell in your body contained not just a genetic blueprint, but also a set of molecular instructions telling it when to activate certain genes, how to respond to environmental changes, and even when to undergo major transformations like flowering. This is the hidden world of epigenetics - a layer of biological control that operates above our genes, determining which ones are switched on or off without changing the underlying DNA sequence. For Lars Hennig, a passionate plant scientist whose life was tragically cut short in 2018, this hidden world became his life's work 1 .
Plants cannot uproot themselves when conditions turn unfavorable. Instead, they rely on sophisticated internal systems to adapt.
Hennig dedicated his career to understanding the molecular mechanisms that allow plants to control their development.
Hennig's work revealed that much of plant control happens at the epigenetic level, through modifications to chromatin - the complex of DNA and proteins that packages genetic information inside cells 1 .
Lars Hennig's scientific path reflects both his intellectual curiosity and his determination to tackle fundamental biological questions. Born in Rostock, Germany in 1970, he began his scientific education at Martin Luther University of Halle-Wittenberg before moving to Albert Ludwigs University of Freiburg in 1996 1 .
Studied plant photoreceptors and their interactions in Eberhard Schäfer's laboratory 1 .
Initially studied cell cycle-regulated gene expression in Wilhelm Gruissem's laboratory 1 .
Focused on chromatin regulation of flowering time 1 .
Continued work on plant developmental epigenetics and Polycomb proteins 1 .
At the heart of Hennig's research program was a fascination with how chromatin-modifying complexes control plant development and environmental responses. His work particularly focused on the Polycomb group proteins, which form complexes that can modify chromatin structure to repress gene expression 1 .
Hennig's research established that MSI1 functions as a subunit of two distinct chromatin-modifying complexes:
Hennig affectionately called MSI1 the 'Swiss-army-knife' of chromatin regulation due to its multiple functions in diverse cellular processes 1 .
To understand the nature of Hennig's scientific contributions, it is valuable to examine one of his key experiments in detail. In 2020, his team published a groundbreaking study in Genome Biology titled "Removal of H2Aub1 by ubiquitin-specific proteases 12 and 13 is required for stable Polycomb-mediated gene repression in Arabidopsis" 6 .
The researchers employed a multi-faceted approach:
| Experimental Approach | Main Result | Biological Significance |
|---|---|---|
| Transcriptome analysis | 1,128 genes misregulated in double mutant | UBP12/13 mainly repress response genes |
| H2Aub1 ChIP-seq | 3% of protein-coding genes gained H2Aub1 | Identified direct targets of UBP12/13 |
| Genetic interactions | Overlap with PRC1, PRC2, EMF1 mutant genes | Places UBP12/13 in Polycomb network |
| H3K27me3 analysis | Loss at specific loci in ubp12/13 mutants | H2Aub1 removal needed for H3K27me3 maintenance |
This work fundamentally advanced our understanding of Polycomb repression by revealing that the removal of an activating mark (H2Aub1) is just as important as the addition of repressive marks (H3K27me3) for stable gene silencing 6 .
Hennig's research relied on sophisticated molecular and biochemical techniques that allowed his team to probe the epigenetic landscape of plants. Throughout his career, he was committed to developing and refining methodological approaches that would benefit the entire plant science community.
| Tool/Technique | Function in Research | Example from Hennig's Work |
|---|---|---|
| Chromatin Immunoprecipitation (ChIP) | Maps histone modifications and protein binding across genome | Used to track H2Aub1 and H3K27me3 changes in mutants 6 |
| Maleimide reagents (e.g., AMS) | Label thiol groups to determine protein redox state | Adapted method for Arabidopsis studies 7 |
| GENEVESTIGATOR | Bioinformatics tool for analyzing gene expression patterns | Co-developed this powerful database and analysis toolbox 2 |
| Affymetrix ATH1 microarray | Genome-wide transcript profiling | Helped develop expanded options for Arabidopsis transcriptomics 1 |
| Histone purification | Isolate histones for modification analysis | Used cauliflower histones to identify novel modifications 1 |
| PlantDB | Database for managing plant experiment documentation | Developed to help researchers organize data and stocks 1 |
Hennig's development of GENEVESTIGATOR was particularly impactful. This database and Web-browser data mining interface for Affymetrix GeneChip data allowed researchers to query gene expression patterns throughout different environmental conditions, growth stages, or organs 2 .
His commitment to methodology extended beyond his immediate research needs. As a skilled biostatistician and bioinformatician, he and his colleagues at ETH Zurich developed pioneering functional genomic tools and established benchmarks for plant researchers 1 .
Though his research career was cut short by illness, Lars Hennig's scientific legacy extends far beyond his own publications. He mentored 11 PhD students and 11 postdoctoral fellows who all successfully continued their own careers 1 .
Former colleagues remember that "as a mentor, Lars was dedicated and caring: he knew how to motivate students and postdocs at times of frustration but he also made them pause and reflect on exciting but preliminary results" 1 .
Hennig played a crucial role in building the plant chromatin community. Together with Valérie Gaudin and Claudia Köhler, he initiated the successful biannual European Workshop Series in Plant Chromatin 1 4 .
His service included roles as associate editor and Flowering Newsletter editor of the Journal of Experimental Botany from 2012 to 2017, and he established the Flowering Highlights blog 1 .
"The atmosphere around Lars was always lively and enjoyable: he liked to mingle with group members, get to know their personality and cultural background, promote discussions, and facilitate collaboration" 1 .
Lars Hennig's work fundamentally advanced our understanding of how plants use chromatin modifications to control their development and respond to environmental challenges. His research revealed the dynamic nature of epigenetic regulation, demonstrating how the careful balancing act of adding and removing histone modifications allows plants to maintain stable gene expression patterns while remaining responsive to changing conditions.
"Despite his conviction that 'life is not designed to be fair' and his doubt about the 'absolute truth' in biology, Hennig's passionate quest for fairness and truth was inspiring to those around him" 1 .
As we continue to face global challenges like climate change and food security, the fundamental knowledge generated by Hennig's research becomes increasingly valuable. Understanding how plants control their development and stress responses at the epigenetic level may hold keys to developing more resilient crops in the future. Though his own time was cut short, the seeds of knowledge planted by Lars Hennig continue to grow and blossom through the work of his students, colleagues, and the entire plant epigenetics community he helped build.