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- Pietra, Stefano, 1980-, et al.
(författare)
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Arabidopsis SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity
- 2013
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 4, s. 2779-
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Tidskriftsartikel (refereegranskat)abstract
- The orientation of cell division and the coordination of cell polarity within the plane of the tissue layer (planar polarity) contribute to shape diverse multicellular organisms. The root of Arabidopsis thaliana displays regularly oriented cell divisions, cell elongation and planar polarity providing a plant model system to study these processes. Here we report that the SABRE protein, which shares similarity with proteins of unknown function throughout eukaryotes, has important roles in orienting cell division and planar polarity. SABRE localizes at the plasma membrane, endomembranes, mitotic spindle and cell plate. SABRE stabilizes the orientation of CLASP-labelled preprophase band microtubules predicting the cell division plane, and of cortical microtubules driving cell elongation. During planar polarity establishment, sabre is epistatic to clasp at directing polar membrane domains of Rho-of-plant GTPases. Our findings mechanistically link SABRE to CLASP-dependent microtubule organization, shedding new light on the function of SABRE-related proteins in eukaryotes.
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| 2. |
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| 3. |
- Pietra, Stefano, 1980-
(författare)
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Characterization of New Players in Planar Polarity Establishment in Arabidopsis
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Coordinated polarity and differentiation of cells in the plane of a tissue layer are essential to the development of multicellular organisms. Arabidopsis thaliana root hairs and trichomes provide model systems to study the pathways that control planar polarity and cell fate specification in plants. A concentration gradient of the plant hormone auxin provides an instructive cue that coordinates polar assembly of signalling complexes at plasma membranes of root epidermal cells; however, knowledge about additional players and cytoskeletal effectors driving cell polarization prior to hair emergence remains limited. On the other hand, epidermal cell fate specification is controlled by a well-characterized gene network of transcription factors that translate positional signals and cell-to-cell communication into tissue-wide patterning. Yet, new components are continuously found to interact with the patterning pathway, shedding light on its connections with diverse developmental processes.This thesis presents the SABRE (SAB) gene as a novel player in planar polarity establishment and root epidermal patterning. SAB is a large protein with sequence similarity to proteins present in all eukaryotes and affects planar polarity as well as orientation of cell divisions and cortical microtubules. Genetic interaction with the microtubule-associated protein gene CLASP further supports involvement of SAB in microtubule arrangement, suggesting a role for this gene in cytoskeletal organisation. Strikingly, SAB also interacts genetically with ACTIN7 (ACT7), and both ACT7 and its modulator ACTIN INTERACTING PROTEIN 1-2 (AIP1-2) contribute to planar polarity of root hair positioning. Cell-file specific expression of AIP1-2 depends on the epidermal-patterning regulator WEREWOLF (WER), revealing a connection between actin organization, planar polarity and cell fate specification. Consistent with this finding, SAB also functions in patterning of the root epidermis by stabilizing cell fate acquisition upstream of the core patterning pathway. These results unveil new roles for SAB in planar polarity and epidermal patterning and suggest that organization of the microtubule and the actin cytoskeleton are important to both planar polarity establishment and cell fate specification.
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| 4. |
- Pietra, Stefano, 1980-, et al.
(författare)
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SABRE is required for stabilization of root hair patterning in Arabidopsis thaliana
- 2015
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Ingår i: Physiologia Plantarum. - : Wiley. - 0031-9317 .- 1399-3054. ; 153:3, s. 440-453
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Tidskriftsartikel (refereegranskat)abstract
- Patterned differentiation of distinct cell types is essential for the development of multicellular organisms. The root epidermis of Arabidopsis thaliana is composed of alternating files of root hair and non-hair cells and represents a model system for studying the control of cell-fate acquisition. Epidermal cell fate is regulated by a network of genes that translate positional information from the underlying cortical cell layer into a specific pattern of differentiated cells. While much is known about the genes of this network, new players continue to be discovered. Here we show that the SABRE (SAB) gene, known to mediate microtubule organization, anisotropic cell growth and planar polarity, has an effect on root epidermal hair cell patterning. Loss of SAB function results in ectopic root hair formation and destabilizes the expression of cell fate and differentiation markers in the root epidermis, including expression of the WEREWOLF (WER) and GLABRA2 (GL2) genes. Double mutant analysis reveal that wer and caprice (cpc) mutants, defective in core components of the epidermal patterning pathway, genetically interact with sab. This suggests that SAB may act on epidermal patterning upstream of WER and CPC. Hence, we provide evidence for a role of SAB in root epidermal patterning by affecting cell-fate stabilization. Our work opens the door for future studies addressing SAB-dependent functions of the cytoskeleton during root epidermal patterning.
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