Dynamo Seminar: Tonni Grube Andersen

DynaMo Semiars are a series of public seminars hosted by DynaMo Center. We are pleased to announce our next seminar speaker:

Tonni Grube Andersen

Université de Lausanne, Switzerland

The endodermal passage cell: Just another brick in the wall?

To maintain a sufficient transport of water and nutrients from the soil, it is crucial for plants to have an efficient barrier system that facilitates uptake and prevents backflow. In old roots, cork-like suberin lamellae are deposited in the cell walls of the endodermis, which is believed to serve as a barrier for transcellular transport. While this deposition occurs in the majority of old endodermal cells, those adjacent to xylem poles do not always undergo suberization. These cells are historically characterized as “passage cells” based on the assumption that they retain capacity for transport in an otherwise sealed area. While occurring in a range of plant species the term passage cell is ill fitting, as our knowledge is purely descriptive. By developing markers that highlight passage cells we discovered that these cells respond to local auxin/cytokinin ratio changes in the nanomolar range, as well as to non-cell autonomous inhibition of cytokinin signaling in the meristem. We found that passage cells are producers of cytokinin while at the same time refractory to cytokinin signaling, which suggest that they share developmental features with xylem. By investigating the expression of nutrient transporters, we emphasize that not only are passage cells a distinct cell type, they likely constitute a nucleation point for trans-cellular channeling of substrates from the rhizosphere to the vasculature. Based on our findings, we argue that not only does the xylem pole endodermis undergo individual programming; the well-established bilateral symmetry of the root stele should be expanded to include cortical layers.

Tonni Grube Andersen is a postdoc at the Niko Geldner lab at Lausanne University. He obtained his Masters and PhD at the DynaMo Center. His previous work includes elucidation of transport and biosynthetic mechanisms of the defense compounds glucosinolates in the model plant Arabidopsis thaliana. After his PhD he continued his work, and investigated protein-protein interactions in glucosinolate biosynthetic pathway using Y2H and FRET-FLIM analyses. Tonni received a Marie Curie postdoc grant to join the Geldner lab in February 2014. Tonni’s current project revolves on transcriptional identity of individual cells in the endodermis and molecular identification of the non-suberized “passage cells”. He aims at characterizing molecular markers for passage cells that will allow us to study the behavior of endodermis cells during a variety of abiotic stresses. To unravel this, he will employ single-cell transcriptomics, functional genomics and live-cell imaging.