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

Roots show positive hydrotropism in response to moisture gradients, which is believed to contribute to plant water acquisition. This article reviews the recent advances of the physiological and molecular genetic studies on hydrotropism in seedling roots of Arabidopsis thaliana. We identified MIZU-KUSSEI1 (MIZ1) and MIZ2, essential genes for hydrotropism in roots; the former encodes a protein of unknown function, and the latter encodes an ARF-GEF (GNOM) protein involved in vesicle trafficking. Because both mutants are defective in hydrotropism but not in gravitropism, these mutations might affect a molecular mechanism unique to hydrotropism. MIZ1 is expressed in the lateral root cap and cortex of the root proper. It is localized as a soluble protein in the cytoplasm and in association with the cytoplasmic face of endoplasmic reticulum (ER) membranes in root cells. Light and ABA independently regulate MIZ1 expression, which influences the ultimate hydrotropic response. In addition, MIZ1 overexpression results in an enhancement of hydrotropism and an inhibition of lateral root formation. This phenotype is likely related to the alteration of auxin content in roots. Specifically, the auxin level in the roots decreases in the MIZ1 overexpressor and increases in the miz1 mutant. Unlike most gnom mutants, miz2 displays normal morphology, growth, and gravitropism, with normal localization of PIN proteins. It is probable that MIZ1 plays a crucial role in hydrotropic response by regulating the endogenous level of auxin in Arabidopsis roots. Furthermore, the role of GNOM/MIZ2 in hydrotropism is distinct from that of gravitropism.
Am J Bot 2013 Jan
PMID:Molecular mechanisms of hydrotropism in seedling roots of Arabidopsis thaliana (Brassicaceae). 2326 56

Polar auxin transport can be likened to water following the path of least resistance as it flows downhill. In the case of auxin, the hill is the difference in electrochemical potential of the auxin anion (IAA(-)). H(+)-ATPases and H(+)-IAA symporters at the plasma membrane create the electrical and IAA(-) concentration gradients that constitute this thermodynamic hill. PIN and ABCB transporters also at the plasma membrane bias the direction and limit the rate of downhill flow out of the cell. This article will present the thermodynamic basis for this view and critically examine how well the molecular biological descriptions of the polar auxin transport process fit the framework. An auxin concentration gradient across an organ has long been recognized as the cause of bending growth during tropisms. Its generation can be viewed as a result of redirected polar auxin transport. This article will examine how molecular regulation of the paths of least resistance to auxin efflux diverts the downhill flow of auxin to steer growth during tropisms.
Am J Bot 2013 Jan
PMID:Diverting the downhill flow of auxin to steer growth during tropisms. 2328 58

Roots play important roles in plant survival and productivity as they not only anchor the plants in the soil but are also the primary organ for the uptake of nutrients from the outside. The growth and development of roots depend on the specification and maintenance of the root meristem. Here, we report a previously unknown role of TIME FOR COFFEE (TIC) in controlling root meristem size in Arabidopsis. The results showed that loss of function of TIC reduced root meristem length and cell number by decreasing the competence of meristematic cells to divide. This was due to the repressed expression of PIN genes for decreased acropetal auxin transport in tic-2, leading to low auxin accumulation in the roots responsible for reduced root meristem, which was verified by exogenous application of indole-3-acetic acid. Downregulated expression of PLETHORA1 (PLT1) and PLT2, key transcription factors in mediating the patterning of the root stem cell niche, was also assayed in tic-2. Similar results were obtained with tic-2 and wild-type plants at either dawn or dusk. We also suggested that the MYC2-mediated jasmonic acid signalling pathway may not be involved in the regulation of TIC in controlling the root meristem. Taken together, these results suggest that TIC functions in an auxin-PLTs loop for maintenance of post-embryonic root meristem.
J Exp Bot 2014 Jan
PMID:TIME FOR COFFEE controls root meristem size by changes in auxin accumulation in Arabidopsis. 2427 77

Understanding the mechanisms by which nutritional signals impact upon root system architecture is a key facet in the drive for greater nutrient application efficiency in agricultural systems. Cereal plants reduce their rate of lateral root emergence under inorganic phosphate (Pi) shortage; this study uses molecular and pharmacological techniques to dissect this Pi response in Triticum aestivum. Plants were grown in coarse sand washed in high- or low-Pi nutrient solution before being assessed for their root branching density and expression of AUX/IAA and PIN genes. Seedlings were also grown on media containing [(14)C]indole acetic acid to measure basipetal auxin transport. Seedlings grown in low-Pi environments displayed less capacity to transport auxin basipetally from the seminal root apex, a reduction in root expression of PIN auxin transporter genes, and perturbed expression of a range of AUX/IAA auxin response genes. Given the known importance of basipetally transported auxin in stimulating lateral root initiation, it is proposed here that, in T. aestivum, Pi availability directly influences lateral root production through modulation of PIN expression. Understanding such processes is important in the drive for greater efficiency in crop use of Pi fertilizers in agricultural settings.
J Exp Bot 2014 Sep
PMID:Phosphate depletion modulates auxin transport in Triticum aestivum leading to altered root branching. 2508 90

Strigolactones (SLs) are plant hormones that regulate the plant response to phosphate (Pi) growth conditions. At least part of SL-signalling execution in roots involves MAX2-dependent effects on PIN2 polar localization in the plasma membrane (PM) and actin bundling and dynamics. We examined PIN2 expression, PIN2 PM localization, endosome trafficking, and actin bundling under low-Pi conditions: a MAX2-dependent reduction in PIN2 trafficking and polarization in the PM, reduced endosome trafficking, and increased actin-filament bundling were detected in root cells. The intracellular protein trafficking that is related to PIN proteins but unassociated with AUX1 PM localization was selectively inhibited. Exogenous supplementation of the synthetic SL GR24 to a SL-deficient mutant (max4) led to depletion of PIN2 from the PM under low-Pi conditions. Accordingly, roots of mutants in MAX2, MAX4, PIN2, TIR3, and ACTIN2 showed a reduced low-Pi response compared with the wild type, which could be restored by auxin (for all mutants) or GR24 (for all mutants except max2-1). Changes in PIN2 polarity, actin bundling, and vesicle trafficking may be involved in the response to low Pi in roots, dependent on SL/MAX2 signalling.
J Exp Bot 2015 Mar
PMID:Arabidopsis response to low-phosphate conditions includes active changes in actin filaments and PIN2 polarization and is dependent on strigolactone signalling. 2560 25

Strigolactones are a new group of plant hormones that suppress shoot branching. In roots, they regulate primary-root growth and lateral-root formation and increase root-hair elongation. Reception of strigolactones occurs via a specific cellular system which includes a D14-like/MAX2-like/SCF complex that, upon perception of strigolactone signalling, leads to certain degradation of receptors and to the release of downstream targets. This signalling pathway may eventually result in changes in actin-filament bundling, cellular trafficking, and PIN localization in the plasma membrane. As a result, auxin flux may be regulated in the shoot or root. Strigolactones are also involved with the response to phosphate conditions in roots, acting by both dampening auxin transport via depletion of PIN2 from the plasma membrane and inducing TIR1 transcription to increase auxin perception. In these instances and, possibly, others, strigolactones manipulate the auxin pathway, affecting its transport, perception or both. However, other mechanisms for strigolactone-regulated plant development and the involvement of other plant hormones are evident.
J Exp Bot 2015 Aug
PMID:Cellular events of strigolactone signalling and their crosstalk with auxin in roots. 2590 Jun 17

Auxin (indole acetic acid) is a multifunctional phytohormone controlling various developmental patterns, morphogenetic processes, and growth behaviours in plants. The transcription-based pathway activated by the nuclear TRANSPORT INHIBITOR RESISTANT 1/auxin-related F-box auxin receptors is well established, but the long-sought molecular mechanisms of non-transcriptional auxin signalling remained enigmatic until very recently. Along with the establishment of the Arabidopsis leaf epidermal pavement cell (PC) as an exciting and amenable model system in the past decade, we began to gain insight into non-transcriptional auxin signalling. The puzzle-piece shape of PCs forms from intercalated or interdigitated cell growth, requiring local intra- and inter-cellular coordination of lobe and indent formation. Precise coordination of this interdigitated pattern requires auxin and an extracellular auxin sensing system that activates plasma membrane-associated Rho GTPases from plants and subsequent downstream events regulating cytoskeletal reorganization and PIN polarization. Apart from auxin, mechanical stress and cytokinin have been shown to affect PC interdigitation, possibly by interacting with auxin signals. This review focuses upon signalling mechanisms for cell polarity formation in PCs, with an emphasis on non-transcriptional auxin signalling in polarized cell expansion and pattern formation and how different auxin pathways interplay with each other and with other signals.
J Exp Bot 2015 Aug
PMID:Pavement cells: a model system for non-transcriptional auxin signalling and crosstalks. 2604 74

The plant hormone auxin plays an essential role in the patterning of plant structures. Biological hypotheses supported by computational models suggest that auxin may fulfil this role by regulating its own transport, but the plausibility of previously proposed models has been questioned. We applied the notion of unidirectional fluxes and the formalism of Petri nets to show that the key modes of auxin-driven patterning-the formation of convergence points and the formation of canals-can be implemented by biochemically plausible networks, with the fluxes measured by dedicated tally molecules or by efflux and influx carriers themselves. Common elements of these networks include a positive feedback of auxin efflux on the allocation of membrane-bound auxin efflux carriers (PIN proteins), and a modulation of this allocation by auxin in the extracellular space. Auxin concentration in the extracellular space is the only information exchanged by the cells. Canalization patterns are produced when auxin efflux and influx act antagonistically: an increase in auxin influx or concentration in the extracellular space decreases the abundance of efflux carriers in the adjacent segment of the membrane. In contrast, convergence points emerge in networks in which auxin efflux and influx act synergistically. A change in a single reaction rate may result in a dynamic switch between these modes, suggesting plausible molecular implementations of coordinated patterning of organ initials and vascular strands predicted by the dual polarization theory.
J Exp Bot 2015 Aug
PMID:Auxin-driven patterning with unidirectional fluxes. 2611 15

The directional transport of auxin, known as polar auxin transport (PAT), allows asymmetric distribution of this hormone in different cells and tissues. This system creates local auxin maxima, minima, and gradients that are instrumental in both organ initiation and shape determination. As such, PAT is crucial for all aspects of plant development but also for environmental interaction, notably in shaping plant architecture to its environment. Cell to cell auxin transport is mediated by a network of auxin carriers that are regulated at the transcriptional and post-translational levels. Here we review our current knowledge on some aspects of the 'non-genomic' regulation of auxin transport, placing an emphasis on how phosphorylation by protein and lipid kinases controls the polarity, intracellular trafficking, stability, and activity of auxin carriers. We describe the role of several AGC kinases, including PINOID, D6PK, and the blue light photoreceptor phot1, in phosphorylating auxin carriers from the PIN and ABCB families. We also highlight the function of some receptor-like kinases (RLKs) and two-component histidine kinase receptors in PAT, noting that there are probably RLKs involved in co-ordinating auxin distribution yet to be discovered. In addition, we describe the emerging role of phospholipid phosphorylation in polarity establishment and intracellular trafficking of PIN proteins. We outline these various phosphorylation mechanisms in the context of primary and lateral root development, leaf cell shape acquisition, as well as root gravitropism and shoot phototropism.
J Exp Bot 2016 07
PMID:Regulation of polar auxin transport by protein and lipid kinases. 2724 71

Plant-parasitic root-knot nematodes induce the formation of giant cells within the plant root, and it has been recognized that auxin accumulates in these feeding sites. Here, we studied the role of the auxin transport system governed by AUX1/LAX3 influx proteins and different PIN efflux proteins during feeding site development in Arabidopsis thaliana roots. Data generated via promoter-reporter line and protein localization analyses evoke a model in which auxin is being imported at the basipetal side of the feeding site by the concerted action of the influx proteins AUX1 and LAX3, and the efflux protein PIN3. Mutants in auxin influx proteins AUX1 and LAX3 bear significantly fewer and smaller galls, revealing that auxin import into the feeding sites is needed for their development and expansion. The feeding site development in auxin export (PIN) mutants was only slightly hampered. Expression of some PINs appears to be suppressed in galls, probably to prevent auxin drainage. Nevertheless, a functional PIN4 gene seems to be a prerequisite for proper nematode development and gall expansion, most likely by removing excessive auxin to stabilize the hormone level in the feeding site. Our data also indicate a role of local auxin peaks in nematode attraction towards the root.
J Exp Bot 2016 08
PMID:Redirection of auxin flow in Arabidopsis thaliana roots after infection by root-knot nematodes. 2731 70


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