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LSSS 2014-2015

2014LSSS2015

Life Sciences Seminar Series

 

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Thomas Laux

Institute of Biology III, University of Freiburg, Germany

Regulation of zygote polarity

Selected Publications

WOX13-like genes are required for reprogramming of leaf and protoplast cells into stem cells in the moss Physcomitrella patens.Sakakibara K, Reisewitz P, Aoyama T, Friedrich T, Ando S, Sato Y, Tamada Y, Nishiyama T, Hiwatashi Y, Kurata T, Ishikawa M, Deguchi H, Rensing SA, Werr W, Murata T, Hasebe M, Laux T
Development 2014 Apr; 141(8):1660-70

Abstract

Many differentiated plant cells can dedifferentiate into stem cells, reflecting the remarkable developmental plasticity of plants. In the moss Physcomitrella patens, cells at the wound margin of detached leaves become reprogrammed into stem cells. Here, we report that two paralogous P. patens WUSCHEL-related homeobox 13-like (PpWOX13L) genes, homologs of stem cell regulators in flowering plants, are transiently upregulated and required for the initiation of cell growth during stem cell formation. Concordantly, Δppwox13l deletion mutants fail to upregulate genes encoding homologs of cell wall loosening factors during this process. During the moss life cycle, most of the Δppwox13l mutant zygotes fail to expand and initiate an apical stem cell to form the embryo. Our data show that PpWOX13L genes are required for the initiation of cell growth specifically during stem cell formation, in analogy to WOX stem cell functions in seed plants, but using a different cellular mechanism.

Accession-specific modifiers act with ZWILLE/ARGONAUTE10 to maintain shoot meristem stem cells during embryogenesis in Arabidopsis.Tucker MR, Roodbarkelari F, Truernit E, Adamski NM, Hinze A, Lohmüller B, Würschum T, Laux T
BMC Genomics 2013; 14:809

Abstract

Stem cells located in the centre of the shoot apical meristem are required for the repetitive formation of new organs such as leaves, branches and flowers. In Arabidopsis thaliana, the ZWILLE/PINHEAD/AGO10 (ZLL) gene encodes a member of the ARGONAUTE (AGO) protein family and is required to maintain shoot meristem stem cells during embryogenesis. In the Landsberg erecta (Ler) acession, ZLL is essential for stem cell maintenance, whereas in the Columbia (Col) accession its requirement appears masked by genetic modifiers. The genetic basis for this variation has remained elusive.

A protodermal miR394 signal defines a region of stem cell competence in the Arabidopsis shoot meristem.Knauer S, Holt AL, Rubio-Somoza I, Tucker EJ, Hinze A, Pisch M, Javelle M, Timmermans MC, Tucker MR, Laux T
Dev. Cell 2013 Jan 28; 24(2):125-32

Abstract

A long-standing question in plants and animals is how spatial patterns are maintained within stem cell niches despite ongoing cell divisions. Here we address how, during shoot meristem formation in Arabidopsis thaliana, the three apical cell layers acquire stem cell identity. Using a sensitized mutant screen, we identified miR394 as a mobile signal produced by the surface cell layer (the protoderm) that confers stem cell competence to the distal meristem by repressing the F box protein LEAF CURLING RESPONSIVENESS. This repression is required to potentiate signaling from underneath the stem cells by the transcription factor WUSCHEL, maintaining stem cell pluripotency. The interaction of two opposing signaling centers provides a mechanistic framework of how stem cells are localized at the tip of the meristem. Although the constituent cells change, the surface layer provides a stable point of reference in the self-organizing meristem.

Arabidopsis WIH1 and WIH2 genes act in the transition from somatic to reproductive cell fate.Lieber D, Lora J, Schrempp S, Lenhard M, Laux T
Curr. Biol. 2011 Jun 21; 21(12):1009-17

Abstract

Unlike animals, higher plants do not establish a germ line in embryo development but form haploid germ cells from diploid somatic cells late in their life cycle. However, despite its prime importance, little is known about how this transition is regulated.

Transcriptional activation of Arabidopsis axis patterning genes WOX8/9 links zygote polarity to embryo development.Ueda M, Zhang Z, Laux T
Dev. Cell 2011 Feb 15; 20(2):264-70

Abstract

In most flowering plants, the apical-basal body axis is established by an asymmetric division of the polarized zygote. In Arabidopsis, early embryo patterning is regulated by WOX homeobox genes, which are coexpressed in the zygote but become restricted to apical (WOX2) and basal (WOX8/9) cells. How the asymmetry of zygote division is regulated and connected to the daughter cell fates is largely unknown. Here, we show that expression of WOX8 is independent of the axis patterning signal auxin, but, together with the redundant gene WOX9, is activated in the zygote, its basal daughter cell, and the hypophysis by the zinc-finger transcription factor WRKY2. In wrky2 mutants, egg cells polarize normally but zygotes fail to reestablish polar organelle positioning from a transient symmetric state, resulting in equal cell division and distorted embryo development. Both defects are rescued by overexpressing WOX8, indicating that WRKY2-dependent WOX8 transcription links zygote polarization with embryo patterning.