Our group is intrigued by green algae/plants and their capability to produce various polysaccharides, many of which are among the most abundant biopolymers known and a key resource of our society (food, fodder, fibre, fuel). With our research, we aim to better understand how plants allocate their carbon to polysaccharides and constantly remodel them via various types of enzymes. We try to use this knowledge to enhance sustainable biomass production.

Green algae store most of their acquired carbon as cell wall polysaccharides, some of which can be detected with probes such as antibodies, lectins or optotracers. However, these probes often have limited access to their targets, insufficient specificity or require invasive sample treatments, which strongly limits our understanding of green algal cell wall structures and dynamics. To overcome these limitations, we are developing metabolic labelling approaches based on non-invasive click chemistry, allowing to detect various algal polysaccharides in vivo. This toolset will help us to study cell wall structural changes and carbon allocation in green algae.

Funding: BMBF

Responsible persons:

• Qian Wang

• Klaus Herburger

Funding Period: 2023 - 2026

Green algae can secrete large amounts of cell wall-derived polysaccharides into the environment. Our preliminary data suggest that a proportion of these external polysaccharides are recruited back into their cell walls via cell wall-bound enzymes. Such polysaccharide routes may have assisted algae in conquering terrestrial habitats, as this process increases the cellular water-holding capacity and potentially opens up an external carbon source. To explore these functions, we are devising a series of cultivation and in vivo-imaging experiments to track polysaccharide routes. This tracking will also consider cross-species exchange of polysaccharides.

Funding: DFG

Responsible persons:

• Barış Ballık

• Klaus Herburger

Funding Period: 2024 - 2027

Cooperation partners

• Prof. Peter Ulvskov (University of Copenhagen)
• Prof. Stephen C. Fry (University of Edinburgh)

Seaweeds such as the worldwide occurring green macroalgae Ulva sp. (Chlorophyta) face harsh environmental conditions in their coastal habitats, yet they produce tremendous biomass accumulations known as “green tides”. The bulk material in these blooms are multi-layered cell walls, which are a polysaccharide-rich matrix that surrounds every cell and constitute up to ~60% of the algal dry matter. Cell walls are the only physical barrier between the sensitive algal protoplast and the environment. This makes them key elements in stress survival, for example, by increasing the water holding capacity of cells or by assisting a controlled shrinkage and expansion during desiccation-rehydration cycles. However, it is largely unknown how the Ulva cell wall composition and architecture respond to external abiotic factors such as water scarcity. This is a fundamental gap in knowledge, because it limits our understanding of how seaweeds cope which stress in coastal habitats and sustain their high ecological significance. To better understand Ulva’s ecological success, we will combine eco-physiological monitoring with state-of-the-art bioimaging and chemical biology tools to investigate how environmental factors shape the composition, remodelling and architecture of the Ulva cell wall. First, we will collect various Ulva thalli from the field and establish stable cultures. Next, we will construct an environmental chamber allowing us to expose Ulva thalli to defined water, temperature, and light stresses typical for coastal habitats. Finally, we will implement imaging and chemical biology tools to visualize and quantify chemical and structural changes of the Ulva cell wall composition due to changing environmental conditions in vivo and in situ. We anticipate that our interdisciplinary approach will allow us to uncover unknown features of seaweed cell wall reorganisation (e.g. enzymatic remodelling of cell wall components), helping us to better understand how seaweeds cope with stress. This will provide crucial information for future seaweed farming efforts that aim to maximize biomass production and provide a foundation for unravelling the molecular basis of cell wall remodelling in seaweeds.

Funding: DFG

Responsible persons:

• Yunyun Pan

• Ulf Karsten

• Klaus Herburger

Funding Period: 2024 - 2027

Cooperation partners:

• Prof. Jozef Mravec (Plant Science and Biodiversity Centre SAS)