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Pietra, Stefano
Publications (7 of 7) Show all publications
Krupinski, P., Bozorg, B., Larsson, A., Pietra, S., Grebe, M. & Jönsson, H. (2016). A Model Analysis of Mechanisms for Radial Microtubular Patterns at Root Hair Initiation Sites. Frontiers in Plant Science, 7, Article ID 1560.
Open this publication in new window or tab >>A Model Analysis of Mechanisms for Radial Microtubular Patterns at Root Hair Initiation Sites
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2016 (English)In: Frontiers in Plant Science, E-ISSN 1664-462X, Vol. 7, article id 1560Article in journal (Refereed) Published
Abstract [en]

Plant cells have two main modes of growth generating anisotropic structures. Diffuse growth where whole cell walls extend in specific directions, guided by anisotropically positioned cellulose fibers, and tip growth, with inhomogeneous addition of new cell wall material at the tip of the structure. Cells are known to regulate these processes via molecular signals and the cytoskeleton. Mechanical stress has been proposed to provide an input to the positioning of the cellulose fibers via cortical microtubules in diffuse growth. In particular, a stress feedback model predicts a circumferential pattern of fibers surrounding apical tissues and growing primordia, guided by the anisotropic curvature in such tissues. In contrast, during the initiation of tip growing root hairs, a star-like radial pattern has recently been observed. Here, we use detailed finite element models to analyze how a change in mechanical properties at the root hair initiation site can lead to star-like stress patterns in order to understand whether a stress-based feedback model can also explain the microtubule patterns seen during root hair initiation. We show that two independent mechanisms, individually or combined, can be sufficient to generate radial patterns. In the first, new material is added locally at the position of the root hair. In the second, increased tension in the initiation area provides a mechanism. Finally, we describe how a molecular model of Rho-of-plant (ROP) GTPases activation driven by auxin can position a patch of activated ROP protein basally along a 2D root epidermal cell plasma membrane, paving the way for models where mechanical and molecular mechanisms cooperate in the initial placement and outgrowth of root hairs.

Place, publisher, year, edition, pages
Frontiers Media, 2016
Keywords
plant cell wall, finite element modeling, computational morphodynamics, root hair initiation, microtubules, cellulose fibers, composite material
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-130023 (URN)10.3389/fpls.2016.01560 (DOI)000386484400001 ()27840629 (PubMedID)2-s2.0-84994462004 (Scopus ID)
Available from: 2017-01-11 Created: 2017-01-11 Last updated: 2024-01-17Bibliographically approved
Kiefer, C. S., Claes, A. R., Nzayisenga, J.-C., Pietra, S., Stanislas, T., Hueser, A., . . . Grebe, M. (2015). Arabidopsis AIP1-2 restricted by WER-mediated patterning modulates planar polarity. Development, 142(1), 151-161
Open this publication in new window or tab >>Arabidopsis AIP1-2 restricted by WER-mediated patterning modulates planar polarity
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2015 (English)In: Development, ISSN 0950-1991, E-ISSN 1477-9129, Vol. 142, no 1, p. 151-161Article in journal (Refereed) Published
Abstract [en]

The coordination of cell polarity within the plane of the tissue layer (planar polarity) is crucial for the development of diverse multicellular organisms. Small Rac/Rho-family GTPases and the actin cytoskeleton contribute to planar polarity formation at sites of polarity establishment in animals and plants. Yet, upstream pathways coordinating planar polarity differ strikingly between kingdoms. In the root of Arabidopsis thaliana, a concentration gradient of the phytohormone auxin coordinates polar recruitment of Rho-of-plant (ROP) to sites of polar epidermal hair initiation. However, little is known about cytoskeletal components and interactions that contribute to this planar polarity or about their relation to the patterning machinery. Here, we show that ACTIN7 (ACT7) represents a main actin isoform required for planar polarity of root hair positioning, interacting with the negative modulator ACTIN-INTERACTING PROTEIN1-2 (AIP1-2). ACT7, AIP1-2 and their genetic interaction are required for coordinated planar polarity of ROP downstream of ethylene signalling. Strikingly, AIP1-2 displays hair cell file-enriched expression, restricted by WEREWOLF (WER)-dependent patterning and modified by ethylene and auxin action. Hence, our findings reveal AIP1-2, expressed under control of the WER-dependent patterning machinery and the ethylene signalling pathway, as a modulator of actin-mediated planar polarity.

Keywords
AIP1, Arabidopsis, WEREWOLF, Actin, Patterning, Planar polarity
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-100147 (URN)10.1242/dev.111013 (DOI)000348240500020 ()25428588 (PubMedID)2-s2.0-84918494344 (Scopus ID)
Funder
Swedish Research Council, 2003-2744
Available from: 2015-02-26 Created: 2015-02-24 Last updated: 2024-04-23Bibliographically approved
Pietra, S., Lang, P. & Grebe, M. (2015). SABRE is required for stabilization of root hair patterning in Arabidopsis thaliana. Physiologia Plantarum, 153(3), 440-453
Open this publication in new window or tab >>SABRE is required for stabilization of root hair patterning in Arabidopsis thaliana
2015 (English)In: Physiologia Plantarum, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 153, no 3, p. 440-453Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Developmental Biology Cell Biology
Research subject
Developmental Biology
Identifiers
urn:nbn:se:umu:diva-87837 (URN)10.1111/ppl.12257 (DOI)000349969500009 ()2-s2.0-84923167112 (Scopus ID)
Funder
Swedish Research Council, 2009-4846
Note

Originally published in manuscript form.

Available from: 2014-04-11 Created: 2014-04-11 Last updated: 2023-03-23Bibliographically approved
Pietra, S. (2014). Characterization of New Players in Planar Polarity Establishment in Arabidopsis. (Doctoral dissertation). Umeå: Umeå University
Open this publication in new window or tab >>Characterization of New Players in Planar Polarity Establishment in Arabidopsis
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Karakterisering av nya aktörer vid etablering av planpolaritet i Arabidopsis
Abstract [en]

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.

Abstract [sv]

Samordning av polaritet och differentiering av celler inom ett vävnadslager är avgörande för utvecklingen av multicellulära organismer. Rothår och bladhår hos Arabidopsis thaliana utgör modellsystem för att studera signalvägar som kontrollerar planpolaritet och specifikation av cellers öde hos växter. En koncentrationsgradient av växthormonet auxin ger en instruktiv signal som koordinerar polär hopsättning av signalkomplex vid plasmamembranet i rotepidermisceller; dock är kunskapen om ytterligare aktörer och hur cytoskelettets aktörer påverkar cellpolaritet innan rothår bildas begränsad. Vad gäller differentieringen av epidermala cellers öde kontrolleras dessa genom ett väl karakteriserat nätverk av transkriptionsfaktorer som överför positionssignaler och cell-till-cell kommunikation till vävnadsomfattande mönsterbildning. Fortfarande hittas dock nya komponenter som interagerar med signalvägarna för mönsterbildning, vilket ger nya insikter om dess förbindelser med diverse utvecklingsprocesser.

Denna avhandling presenterar genen SABRE (SAB) som en ny aktör i etableringen av planpolaritet och mönsterbildning av rotepidermis. SAB är ett stort protein som har sekvenslikhet med proteiner som finns i alla eukaryoter och det påverkar planpolaritet, orientering av celldelning och kortikala mikrotubler. Genetisk interaktion med genen för det mikrotubuli-associerade proteinet CLASP stärker ytterligare inblandningen av SAB i organiserandet av mikrotubler och antyder att denna gen har en roll i organiserandet av cytoskelettet. Slående är att SAB även interagerar genetiskt med ACTIN7 (ACT7) och att både ACT7 och dess modulator ACTIN-INTERACTING PROTEIN1-2 (AIP1-2) bidrar till planpolaritet vid positionering av rothår. Cellfils-specifikt uttryck av AIP1-2 beror på den epidermala mönsterbildande genen WEREWOLF (WER), vilket påvisar ett samband mellan organisationen av aktin, planpolaritet och specifikationen av cellers öde. SAB fungerar även i mönsterbildning av rotens epidermis och stabiliserar förvärvet av cellöde uppströms av den centrala signalvägen för mönsterbildning. Dessa resultat visar på nya roller för SAB i planpolaritet och mönsterbildning av epidermis och indikerar att organiseringen av mikrotubler och aktin-cytoskelettet är viktiga både för etablerandet av planpolaritet och för specificeringen av cellers öde.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2014. p. 71
Keywords
SABRE, planar polarity, CLASP, cell division orientation, microtubule cytoskeleton, actin, AIP1, patterning
National Category
Developmental Biology Cell Biology
Research subject
Developmental Biology
Identifiers
urn:nbn:se:umu:diva-87838 (URN)978-91-7601-050-1 (ISBN)
Public defence
2014-05-09, KBC huset, Stora hörsalen KB3B1, Umeå universitet, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2014-04-17 Created: 2014-04-11 Last updated: 2018-06-08Bibliographically approved
Pietra, S., Gustavsson, A., Kiefer, C., Kalmbach, L., Hörstedt, P., Ikeda, Y., . . . Grebe, M. (2013). Arabidopsis SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity. Nature Communications, 4, 2779
Open this publication in new window or tab >>Arabidopsis SABRE and CLASP interact to stabilize cell division plane orientation and planar polarity
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2013 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 4, p. 2779-Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Nature Publishing Group, 2013
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-85312 (URN)10.1038/ncomms3779 (DOI)000328023900017 ()2-s2.0-84889562507 (Scopus ID)
Funder
Swedish Research Council, 2006-522, 2009-4846Knut and Alice Wallenberg Foundation
Available from: 2014-02-05 Created: 2014-01-31 Last updated: 2023-03-28Bibliographically approved
Pietra, S. & Grebe, M. (2010). Auxin paves the way for planar morphogenesis. Cell, 143(1), 29-31
Open this publication in new window or tab >>Auxin paves the way for planar morphogenesis
2010 (English)In: Cell, ISSN 0092-8674, E-ISSN 1097-4172, Vol. 143, no 1, p. 29-31Article in journal (Refereed) Published
National Category
Botany
Research subject
Physiological Botany
Identifiers
urn:nbn:se:umu:diva-37350 (URN)10.1016/j.cell.2010.09.029 (DOI)000282362000010 ()2-s2.0-77957226628 (Scopus ID)
Available from: 2010-10-28 Created: 2010-10-28 Last updated: 2023-03-24Bibliographically approved
Stanislas, T., Hüser, A., Kiefer, C., Brackmann, K., Barbosa, I. C. .., Gustavsson, A., . . . Grebe, M.D6PK AGCVIII kinase is a lipid domain-dependent mediator of Arabidopsis planar polarity.
Open this publication in new window or tab >>D6PK AGCVIII kinase is a lipid domain-dependent mediator of Arabidopsis planar polarity
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(English)Manuscript (preprint) (Other academic)
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-92856 (URN)
Available from: 2014-09-07 Created: 2014-09-07 Last updated: 2018-06-07Bibliographically approved
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