Welcome to Henrik Buschmann’s website!

My research interest focuses on the question how the microtubule system controls the polarity of cell division and cell expansion.

Microtubules may be considered the “read out” of polarity because they align according to polarity cues and then fulfil tasks that fix polarity permanently: they control cell wall assembly / the direction of cell growth and they decide on the plane of cell division.

We know relatively little about the upstream signals that target the plant microtubule system and provide polarity cues. Some signalling components known from animals and fungi are missing in plant genomes, e.g. cdc42 and the PAR signalling complex. However, there is some evidence that phytohormone signalling and ROP-type small GTPases target the plant microtubule system. Additional signalling with potential roles in polarity include MAPK cascades and cyclin dependant kinases.

I have been working on a class of mutants that show obvious defects in organ polarity: helical growth mutants of Arabidopsis. Most helical growth mutants, such as tortifolia mutants / spiral mutants etc., are defective in microtubule-associated proteins or tubulin itself. The twisting phenotype of mutant organs appears to be based on defects in cell expansion. My work revealed the first plant-specific microtubule-associated protein, TORTIFOLIA1. Because the TORTIFOLIA1 protein is required for wild-type polarity of interphase microtubules (Buschmann et al. 2004) one may speculate that plants utilize this class of proteins in order to regulate microtubule alignment.

My current research centres on how plants control the plane of cytokinesis. The control over the alignment of the division plane is of paramount importance because the rigid cell wall of immobile plant cells prevents cell migration or re-orientation of the daughter cells.

Abnormal division patterns therefore lead to dramatic phenotypes including the loss or addition of tissue layers. Well known Arabidopsis mutants with defects in division plane alignment include e.g. bodenlos, orc and scarecrow, but also the cytoskeletal mutants pok, fass, ton1, and tan.

In plant cells, mitosis is preceded by the formation of a band of microtubules that indicates the equator of the division to come. This peculiar ring of microtubules is termed the pre-prophase band (PPB). PPB alignment is thought to depend on nuclear position. At the onset of mitosis the PPB disappears and the microtubules form the mitotic spindle. However, the PPB has left behind a mark at the cell’s cortex that during cytokinesis attracts the outgrowing phragmoplast. The PPB therefore not only indicates but also determines the plane of cell division.

AIR9 is a novel protein involved in plant cell division (Buschmann et al. 2006). AIR9 localization during the transition from prophase to cytokinesis is complex. AIR9 labels the PPB but does not bind to spindle microtubules. At cytokinesis AIR9 behaves like a membrane protein in that it migrates along the new cross wall forming an “AIR9 torus”. We found that the microtubule-binding domain and the domain required for AIR9 torus formation locate to separate regions within the AIR9 protein. Experimental interference with phragmoplast function using drugs that split or dissolve the phragmoplast showed that AIR9 is capable of recognizing the PPB memory. In fact, membrane binding of AIR9 is regulated through the PPB memory (unpublished results).

Some recent publications by Henrik Buschmann:

Buschmann, H., Green, P., Sambade, A., Doonan, J.H., Lloyd, C.W. 2010. Cytoskeletal dynamics in interphase, mitosis and cytokinesis analysed through Agrobacterium-mediated transient transformation of tobacco BY-2 cells. New Phytologist, published online 23 December.

Buschmann, H., Sambade, A., Pesquet, E., Calder, G., Lloyd, C.W. 2010. Microtubule dynamics in plant cells. Book chapter in Methods in Cell Biology, Editor: Lynne Cassimeris. Vol. 97: 373-400.

Buschmann, H., Hauptmann, M., Niessing, D., Lloyd, C.W. and Schäffner, A.R. 2009. Helical growth of Arabidopsis mutant tortifolia2 does not depend on cell division patterns but involves handed twisting of isolated cells. Plant Cell 21: 2090-2106.

Buschmann, H. and Lloyd. C.W. 2008. Arabidopsis mutants and the network of microtubule-associated functions. Review. Molecular Plant 1: 888-898.

Lloyd, C.W. and Buschmann, H. 2007. Plant division: remembering where to build the wall. Review. Current Biology 17: 1053-1055.

Huska, M.R., Buschmann, H. and Andrade-Navarro, M.A. 2007. BiasViz: Visualization of amino acid biased regions in protein alignments. Bioinformatics 23: 3093-3094.

Korolev, A.V., Buschmann, H., Doonan, J.H. and Lloyd, C.W. 2007. AtMAP70-5, a divergent member of the MAP70 family of microtubule-associated proteins, is required for anisotropic cell growth in Arabidopsis. Journal of Cell Science. 120: 2241-2247.

Buschmann, H., Sanchez-Pulido, L., Andrade-Navarro, M.A. and Lloyd, C.W. 2007. Homologues of Arabidopsis microtubule-associated AIR9 in trypanosomatid parasites: Hints on evolution and function. Plant Signaling & Behavior 2: 1-4.

Buschmann, H., Chan, J., Sanchez-Pulido, L., Andrade-Navarro, M.A., Doonan J.H., and Lloyd, C.W. 2006. Microtubule-associated AIR9 recognizes the cortical division site at preprophase and cell-plate insertion. Current Biology 16: 1938-1943.

Mao G., Buschmann H., Doonan J.H., and Lloyd C.W. 2006. The role of MAP65-1 in microtubule bundling during Zinnia tracheary element formation. Journal of Cell Science 119: 753-758.

Buschmann, H., Fabri, C.O., Hauptmann, M., Hutzler, P., Laux, T., Lloyd, C.W. and Schäffner, A.R. 2004. Helical Growth of the Arabidopsis mutant tortifolia1 reveals a plant-specific microtubule-associated protein. Current Biology 14: 1515-1521.

The Lloyd Lab

Welcome to Henrik Buschmann’s website!

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Some recent publications by Henrik Buschmann: