ViPS Invited Seminar March 2019

Thomas Greb, University of Heidelberg, Germany

Date: 13th March 2019

Time: 13:15

Title: Radial Plant Growth - cellular coordination during growth in two dimensions

Location: Seminar room 1015, Biocentre 2, Viikinkaari 5

Host: Ari-Pekka Mähönen

Abstract: Body shaping in multicellular organisms depends on the activity of distinct stem cell niches coordinated over long distances. Radial growth of plant shoots and roots is a stem cell-driven process fundamental for the mechanical and physiological support of enlarging plant bodies. In most dicotyledonous species, the underlying stem cell niche, the cambium, displays a strictly bifacial character generating xylem (wood) inwards and phloem (bast) outwards. Despite its importance and intriguing dynamics, the functional characterization of cambium stem cells was hampered by the lack of experimental tools for accessing distinct cambium sub-domains. Investigating the hypocotyl of Arabidopsis thaliana, we mapped stem cell activity in the proliferating cambium. Through pulse-labelling and genetically encoded lineage tracing, we established different transgenic markers defining a proximal, a central and a distal cambium domain. We further demonstrated that the proximal domain represents a site of xylem formation and the distal cambium domain contains cells determined for phloem development. Moreover, using tissue-specific transcriptomics, chromatin analysis and local genetic perturbation, we unravelled regulatory circuits specifically regulating the transition of common stem cells to xylem or phloem tissues. Thereby, our analysis provides a cellular fate map of a strictly organized plant meristem and reveals determinants instructive for a bifacial tissue production.

Radial growth of plant shoots and roots is essential for the formation of wood and of large plant bodies, and thus for the creation of biomass on earth. The Greb lab uses this process as an example to reveal principles of growth and cell fate regulation in multicellular organisms. This aim is followed by genetic, transcriptional, biochemical and computational tools and by using Arabidopsis thaliana as a research model.

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Related publications:

Shi D, et al. (2019) Bifacial cambium stem cells generate xylem and phloem during radial plant growth. Development 146: dev171355.

Brackmann K, et al. (2018) Spatial specificity of auxin responses coordinates wood formation. Nat Commun 9(1):875.

Wallner ES, et al. (2017) Strigolactone and karrikin-independent SMXL proteins are central regulators of phloem formation. Curr Biol 27(8):1241–1247.

Agusti J, et al. (2011) Strigolactone signaling is required for auxin-dependent stimulation of secondary growth in plants. PNAS USA 108:20242-20247.