Research

How plants master their cell logistics: New insights into transport pathways in the model plant Arabidopsis thaliana Every living cell relies on a precisely coordinated transport system to maintain its diverse functions. This intracellular transport system ensures that the right proteins arrive at the right place at the right time and determines which molecules go where and when damaged or no longer needed components are broken down. In plant cells, this logistics system is particularly versatile. It not only influences fundamental processes such as cell growth and cell division, but also enables rapid adaptation to changing environmental conditions such as drought stress, cold, or pest infestation. Despite their fundamental importance, many details of these cellular transport pathways are still not fully understood. This research project focuses on so-called TOL proteins (TARGET OF MYB1-LIKE), which perform important tasks in the organization of cellular transport pathways in the model plant Arabidopsis thaliana. Until now, it was assumed that these proteins were mainly involved in sorting membrane proteins destined for degradation towards the vacuole. However, recent findings show that certain TOL proteins, in particular TOL3, TOL6, and TOL9, are significantly more versatile. Plants lacking these three proteins not only show disturbances in transport to the lytic vacuole, but also defects in transport to storage organelles, in secretion, and in the degradation of damaged cell components by autophagy. The aim of this project is to investigate the individual functions of these TOL proteins in detail and to clarify their role in the various transport pathways. Particular attention is being paid to TOL3, whose cellular distribution, interaction partners, and functional domains are being investigated. State-of-the-art methods from genetics, biochemistry, and novel imaging techniques are being used for this purpose. Microscopic techniques enable the precise localization of the proteins and the analysis of their interactions with known transport complexes. Genetic crosses and pharmacological treatments help to better understand the respective contributions of TOL proteins to specific transport pathways. This project sheds light on fundamental mechanisms of cellular logistics in plants, which have been little researched to date. In the long term, the findings can be used to specifically influence the cellular transport network, with possible applications in plant breeding, for example to improve stress tolerance and yield.

Imagine a tiny, complex machine inside a cell that acts like a pump, letting essential particles flow in and out to maintain the perfect balance for the cell's survival. This tiny pump, known as V-ATPase, is crucial for many vital processes in cells, from protein degradation to maintaining the correct acidity levels. But studying this pump in animals and humans is extremely challenging because, if it doesn't work, the organism die. This is where the uniqueness of plants comes in! Plants have an additional family of pumps that can step in when V-ATPase is not functioning. This allows us to learn more about V-ATPase without harming the organism. My team and I have developed an innovative technique using advanced microscopy to study V-ATPase in plants, opening up new possibilities for understanding how this pump works. This research has potential far-reaching implications, from gaining a better understanding of how plants have evolved to survive in diverse environments, to new ways to protect our crops in the face of climate change. In addition to our work on V-ATPase, we are also exploring the fascinating world of autophagy in plants. Autophagy is a process where a cell recycles its own components to survive under stress conditions. There are two main types of autophagy – canonical and non-canonical. Canonical autophagy involves the formation of a double-membraned vesicle called an autophagosome, which engulfs cellular components for recycling. Non-canonical autophagy, on the other hand, doesn't involve the formation of an autophagosome. Instead, cellular components are directly going to the vacuole, where the V-ATPase is located at. Our work focuses on understanding the role of V-ATPase in non-canonical autophagy. We believe that this process plays a crucial role in plant survival, especially under stress conditions. By unraveling the intricacies of non-canonical autophagy, we hope to shed light on new ways to improve plant resilience and productivity. And our knowledge on the V-ATPase will be helpful not only for plant research, but the global scientific community. I am excited to embark on this journey to uncover the secrets of this tiny but mighty cellular pump.

Wider research context: Polarity acquisition in cellular and organismal context defines differentiation processes in organisms. Higher plants are no exception, with numerous processes driving polar protein deposition to adjust intercellular communication and adaptation to the plants' environment. Canonical PIN-FORMED (PIN) transport proteins are among the most intensely studied polarly localized proteins in plants, exhibiting variable accumulation at different plasma membrane domains, thereby shaping directional cellular efflux of the plant growth regulator auxin. Control of polar PIN localization is central to polarity acquisition and differentiation processes, and our recent work identified the small WAV3 Arabidopsis family of E3 ubiquitin ligases as determinants of apical-basal cellular PIN deposition. Specifically, combinatorial loss of WAV3/WAVH genes causes basal localization of otherwise apically localized PINs. However, mechanisms of WAV3/WAVH-PIN crosstalk are unknown. Objectives: We intend to characterize molecular principles by which WAV3 and closely related proteins control PIN polarity acquisition. Based on our preliminary work, we aim to position WAV3 proteins in regulatory networks of protein sorting and auxin signaling and will test a hypothetical function of WAV3 as positional determinant in polarity establishment.