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Query: UMLS:C0282612 (PIN)
 2,291 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Development in multicellular organisms depends on the ability of individual cells to coordinate their behavior by means of small signaling molecules to form correctly patterned tissues. In plants, a unique mechanism of directional transport of the signaling molecule auxin between cells connects cell polarity and tissue patterning and thus is required for many aspects of plant development. Direction of auxin flow is determined by polar subcellular localization of PIN auxin efflux transporters. Dynamic PIN polar localization results from the constitutive endocytic cycling to and from the plasma membrane, but it is not well understood how this mechanism connects to regulators of cell polarity. The Rho family small GTPases ROPs/RACs are master regulators of cell polarity, however their role in regulating polar protein trafficking and polar auxin transport has not been established. Here, by analysis of mutants and transgenic plants, we show that the ROP interactor and polarity regulator scaffold protein ICR1 is required for recruitment of PIN proteins to the polar domains at the plasma membrane. icr1 mutant embryos and plants display an a array of severe developmental aberrations that are caused by compromised differential auxin distribution. ICR1 functions at the plasma membrane where it is required for exocytosis but does not recycle together with PINs. ICR1 expression is quickly induced by auxin but is suppressed at the positions of stable auxin maxima in the hypophysis and later in the embryonic and mature root meristems. Our results imply that ICR1 is part of an auxin regulated positive feedback loop realized by a unique integration of auxin-dependent transcriptional regulation into ROP-mediated modulation of cell polarity. Thus, ICR1 forms an auxin-modulated link between cell polarity, exocytosis, and auxin transport-dependent tissue patterning.
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PMID:A rho scaffold integrates the secretory system with feedback mechanisms in regulation of auxin distribution. 2038 60

In plants, polar transport of the hormone auxin between cells connects cell polarity and pattern formation and is thus required for plant development. The direction of auxin transport is determined by polar localization of PIN auxin efflux transporters. The dynamic polar localization of PIN proteins depends on constitutive endocytic recycling to and from the plasma membrane. However, it was not well understood how PIN polarization is connected to regulators of cell polarity. In a paper that was published in the January issue of PLoS Biology, 2010 we described the involvement of the ROP GTPase associated scaffold Interactor of Constitutive active ROP 1 (ICR1) in recruitment of PIN proteins to polar domains in the plasma membrane. icr1 mutant plants and embryos have severe developmental aberrations that are caused by abnormal auxin distribution. ICR1 functions at or close to the plasma membrane where it is required for exocytosis. ICR1 transcription is quickly induced by auxin but is post-transcriptionally repressed at the site of stable auxin maximum in embryos and roots. Thus, ICR1 integrates auxin-regulated transcription with ROP modulated cell polarity.
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PMID:An auxin regulated positive feedback loop integrates Rho modulated cell polarity with pattern formation. 2009 22

AUXIN BINDING PROTEIN 1 (ABP1) has long been proposed as an auxin receptor to regulate cell expansion. The embryo lethality of ABP1-null mutants demonstrates its fundamental role in plant development, but also hinders investigation of its involvement in post-embryonic processes and its mode of action. By taking advantage of weak alleles and inducible systems, several recent studies have revealed a role for ABP1 in organ development, cell polarization, and shape formation. In addition to its role in the regulation of auxin-induced gene expression, ABP1 has now been shown to modulate non-transcriptional auxin responses. ABP1 is required for activating two antagonizing ROP GTPase signaling pathways involved in cytoskeletal reorganization and cell shape formation, and participates in the regulation of clathrin-mediated endocytosis to subsequently affect PIN protein distribution. These exciting discoveries provide indisputable evidence for the auxin-induced signaling pathways that are downstream of ABP1 function, and suggest intriguing mechanisms for ABP1-mediated polar cell expansion and spatial coordination in response to auxin.
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PMID:Is ABP1 an auxin receptor yet? 2171 49

Mechanisms governing dynamic protein recycling include small GTPases that activate/inactivate their partner proteins to affect cytoskeletal dynamics, and thereby polar growth, asymmetric cell shape and physiological responses to external stimuli. Three recent studies illustrate the control of PIN endocytosis by ROP-RIC activity in leaf pavement cells and root cells.
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PMID:Vesicle trafficking: ROP-RIC roundabout. 2268 61

ROPs (Rho of plants) belong to a large family of plant-specific Rho-like small GTPases that function as essential molecular switches to control diverse cellular processes including cytoskeleton organization, cell polarization, cytokinesis, cell differentiation and vesicle trafficking. Although the machineries of vesicle trafficking and cell polarity in plants have been individually well addressed, how ROPs co-ordinate those processes is still largely unclear. Recent progress has been made towards an understanding of the co-ordination of ROP signalling and trafficking of PIN (PINFORMED) transporters for the plant hormone auxin in both root and leaf pavement cells. PIN transporters constantly shuttle between the endosomal compartments and the polar plasma membrane domains, therefore the modulation of PIN-dependent auxin transport between cells is a main developmental output of ROP-regulated vesicle trafficking. The present review focuses on these cellular mechanisms, especially the integration of ROP-based vesicle trafficking and plant cell polarity.
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PMID:Rho-GTPase-regulated vesicle trafficking in plant cell polarity. 2445 Jun 54

Cell polarity, often associated with polarized cell expansion/growth in plants, describes the uneven distribution of cellular components, such as proteins, nucleic acids, signaling molecules, vesicles, cytoskeletal elements, and organelles, which may ultimately modulate cell shape, structure, and function. Pollen tubes and root hairs are model cell systems for studying the molecular mechanisms underlying sustained tip growth. The formation of intercalated epidermal pavement cells requires excitatory and inhibitory pathways to coordinate cell expansion within single cells and between cells in contact. Strictly controlled cell expansion is linked to asymmetric cell division in zygotes and stomatal lineages, which require integrated processes of pre-mitotic cellular polarization and division asymmetry. While small GTPase ROPs are recognized as fundamental signaling switches for cell polarity in various cellular and developmental processes in plants, the broader molecular machinery underpinning polarity establishment required for asymmetric division remains largely unknown. Here, we review the widely used ROP signaling pathways in cell polar growth and the recently discovered feedback loops with auxin signaling and PIN effluxers. We discuss the conserved phosphorylation and phospholipid signaling mechanisms for regulating uneven distribution of proteins, as well as the potential roles of novel proteins and MAPKs in the polarity establishment related to asymmetric cell division in plants.
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PMID:Focusing on the focus: what else beyond the master switches for polar cell growth? 2574 59