Date: 13th January 2021
Title: Anionic phospholipids across scales: from plasma membrane nanodomains to plant development
Location: Remotely via Zoom
Host: Michael Wrzaczek
Abstract: My group focuses on the role of anionic phospholipids in membrane signaling, cellular homeostasis, and plant development. Using Arabidopsis as a model system, we established that two anionic lipids, PI4P and PS: i) partition between the plasma membrane (PM) and the trans-Golgi Network (TGN, which is also the early endosome in plants) (Simon et al., 2014 Plant J, Simon et al., 2016 Nature Plants), ii) are concomitantly required to establish the identity of the TGN (Platre et al., 2018 Dev Cell) and iii) the PM/TGN balance of these two lipids are regulated during root development and in response to the plant hormone auxin (Platre et al., 2019 Science). Indeed, PS mainly accumulates at the PM in the root meristem, while it partitions more evenly between the PM and the TGN in the elongation zone. This PM/TGN balance is rapidly regulated (within a few minutes) in response to exogenous treatments by the plant hormone auxin and during root gravitropism. We further showed that the developmental variations in PS subcellular patterns are functionally relevant for the signaling activities of the small GTPase Rho-of-Plant6 (ROP6) in the root (Platre et al., 2019 Science), which is involved in root gravitropism downstream of auxin. The levels of PS at the cell surface grades the amount of ROP6 present in PM nanoclusters, which represent the fraction of ROP6 that are competent for signaling.
We are now focusing on the molecular mechanisms that pattern lipid distribution in the cell and in tissues. In particular, we want to understand how PI4P and PS distributions are established and what are the consequences of their mislocalization at the cellular and developmental levels. To tackle these questions, we use an integrative approach that combines biochemistry, genetics, quantitative live imaging, and super-resolution microscopy together with various phenotypic analyses.