Arabidopsis PIN2 protein directs transport of the phytohormone auxin from the root tip into the root elongation zone. Variation in hormone transport, which depends on a delicate interplay between PIN2 sorting to and from polar plasma membrane domains, determines root growth. By employing a constitutively degraded version of PIN2, we identify brassinolides as antagonists of PIN2 endocytosis. This response does not require de novo protein synthesis, but involves early events in canonical brassinolide signaling. Brassinolide-controlled adjustments in PIN2 sorting and intracellular distribution governs formation of a lateral PIN2 gradient in gravistimulated roots, coinciding with adjustments in auxin signaling and directional root growth. Strikingly, simulations indicate that PIN2 gradient formation is no prerequisite for root bending but rather dampens asymmetric auxin flow and signaling. Crosstalk between brassinolide signaling and endocytic PIN2 sorting, thus, appears essential for determining the rate of gravity-induced root curvature via attenuation of differential cell elongation.

• MeSH
• Arabidopsis účinky léků   metabolismus   MeSH
• biologický transport účinky léků   MeSH
• brassinosteroidy metabolismus   farmakologie   MeSH
• endocytóza účinky léků   MeSH
• gravitropismus účinky léků   fyziologie   MeSH
• kořeny rostlin účinky léků   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• meristém účinky léků   metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• regulátory růstu rostlin metabolismus   farmakologie   MeSH
• signální transdukce MeSH
• steroidy heterocyklické metabolismus   farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Directional organ growth allows the plant root system to strategically cover its surroundings. Intercellular auxin transport is aligned with the gravity vector in the primary root tips, facilitating downward organ bending at the lower root flank. Here we show that cytokinin signaling functions as a lateral root specific anti-gravitropic component, promoting the radial distribution of the root system. We performed a genome-wide association study and reveal that signal peptide processing of Cytokinin Oxidase 2 (CKX2) affects its enzymatic activity and, thereby, determines the degradation of cytokinins in natural Arabidopsis thaliana accessions. Cytokinin signaling interferes with growth at the upper lateral root flank and thereby prevents downward bending. Our interdisciplinary approach proposes that two phytohormonal cues at opposite organ flanks counterbalance each other's negative impact on growth, suppressing organ growth towards gravity and allow for radial expansion of the root system.

• MeSH
• Arabidopsis fyziologie   MeSH
• celogenomová asociační studie MeSH
• cytokininy metabolismus   MeSH
• geneticky modifikované rostliny fyziologie   MeSH
• genom rostlinný genetika   MeSH
• gravitropismus MeSH
• kořeny rostlin metabolismus   MeSH
• oxidoreduktasy genetika   metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• proteolýza MeSH
• regulátory růstu rostlin metabolismus   MeSH
• systémová biologie MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

distribution of auxin within plant tissues is of great importance for developmental plasticity, including root gravitropic growth. Auxin flow is directed by the subcellular polar distribution and dynamic relocalisation of auxin transporters such as the PIN-FORMED (PIN) efflux carriers, which can be influenced by the main natural plant auxin indole-3-acetic acid (IAA). Anthranilic acid (AA) is an important early precursor of IAA and previously published studies with AA analogues have suggested that AA may also regulate PIN localisation. Using Arabidopsis thaliana as a model species, we studied an AA-deficient mutant displaying agravitropic root growth, treated seedlings with AA and AA analogues and transformed lines to over-produce AA while inhibiting its conversion to downstream IAA precursors. We showed that AA rescues root gravitropic growth in the AA-deficient mutant at concentrations that do not rescue IAA levels. Overproduction of AA affects root gravitropism without affecting IAA levels. Treatments with, or deficiency in, AA result in defects in PIN polarity and gravistimulus-induced PIN relocalisation in root cells. Our results revealed a previously unknown role for AA in the regulation of PIN subcellular localisation and dynamics involved in root gravitropism, which is independent of its better known role in IAA biosynthesis.

• MeSH
• Arabidopsis účinky léků   metabolismus   MeSH
• chinolony farmakologie   MeSH
• gravitropismus fyziologie   MeSH
• kořeny rostlin anatomie a histologie   účinky léků   růst a vývoj   fyziologie   MeSH
• kyseliny indoloctové chemie   metabolismus   MeSH
• mutace genetika   MeSH
• ortoaminobenzoáty chemie   metabolismus   farmakologie   MeSH
• polarita buněk * účinky léků   MeSH
• proteiny huseníčku metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Polar auxin transport plays a pivotal role in plant growth and development. PIN-FORMED (PIN) auxin efflux carriers regulate directional auxin movement by establishing local auxin maxima, minima, and gradients that drive multiple developmental processes and responses to environmental signals. Auxin has been proposed to modulate its own transport by regulating subcellular PIN trafficking via processes such as clathrin-mediated PIN endocytosis and constitutive recycling. Here, we further investigated the mechanisms by which auxin affects PIN trafficking by screening auxin analogs and identified pinstatic acid (PISA) as a positive modulator of polar auxin transport in Arabidopsis (Arabidopsis thaliana). PISA had an auxin-like effect on hypocotyl elongation and adventitious root formation via positive regulation of auxin transport. PISA did not activate SCFTIR1/AFB signaling and yet induced PIN accumulation at the cell surface by inhibiting PIN internalization from the plasma membrane. This work demonstrates PISA to be a promising chemical tool to dissect the regulatory mechanisms behind subcellular PIN trafficking and auxin transport.

• MeSH
• Arabidopsis účinky léků   metabolismus   MeSH
• biologický transport účinky léků   MeSH
• buněčná membrána účinky léků   metabolismus   MeSH
• endocytóza * účinky léků   MeSH
• fenotyp MeSH
• fenylacetáty farmakologie   MeSH
• gravitropismus účinky léků   MeSH
• hypokotyl účinky léků   růst a vývoj   MeSH
• kořeny rostlin účinky léků   růst a vývoj   MeSH
• kyseliny indoloctové metabolismus   MeSH
• proteiny huseníčku metabolismus   MeSH
• signální transdukce MeSH
• výhonky rostlin metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Intercellular distribution of the plant hormone auxin largely depends on the polar subcellular distribution of the plasma membrane PIN-FORMED (PIN) auxin transporters. PIN polarity switches in response to different developmental and environmental signals have been shown to redirect auxin fluxes mediating certain developmental responses. PIN phosphorylation at different sites and by different kinases is crucial for PIN function. Here we investigate the role of PIN phosphorylation during gravitropic response. Loss- and gain-of-function mutants in PINOID and related kinases but not in D6PK kinase as well as mutations mimicking constitutive dephosphorylated or phosphorylated status of two clusters of predicted phosphorylation sites partially disrupted PIN3 phosphorylation and caused defects in gravitropic bending in roots and hypocotyls. In particular, they impacted PIN3 polarity rearrangements in response to gravity and during feed-back regulation by auxin itself. Thus PIN phosphorylation, besides regulating transport activity and apical-basal targeting, is also important for the rapid polarity switches in response to environmental and endogenous signals.

• MeSH
• Arabidopsis účinky léků   fyziologie   MeSH
• fosforylace MeSH
• gravitropismus * MeSH
• kořeny rostlin účinky léků   fyziologie   MeSH
• kyseliny indoloctové farmakologie   MeSH
• percepce tíhy MeSH
• polarita buněk * MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulátory růstu rostlin farmakologie   MeSH
• sekvence aminokyselin MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Východiska: Diseminace nádorových buněk z ložiska primárního nádoru a zakládání vzdálených metastáz, u nichž je úspěšnost terapie již velmi omezená, je nejčastější příčinou úmrtí onkologických pacientů. Samotný primární nádor je tvořen heterogenní populací buněk, na něž působí různé selekční tlaky v podobě aktivity imunitního systému, sníženého přísunu živin a kyslíku, chemoterapie, radioterapie atd., které vedou k postupnému převládnutí rezistentních, přizpůsobivých nádorových buněk. Další selekce nastává při metastatickém procesu a díky ní přežívají ve vzdálených ložiscích, zakládaných v různých tkáních, jen buňky schopné se na nové prostředí úspěšně adaptovat a proliferovat v něm. Cíl: Cílem tohoto přehledového článku je představit jednotlivé kroky metastatické kaskády, které musí invazivní buňka překonat, a mechanizmy a signální dráhy, které k tomu využívá. Metastazování je v podstatě velmi neefektivní proces a jen velmi malý zlomek buněk z těch, které opustily primární nádor, v něm uspějí. Důležitou podporu jim při tom poskytují nejen pro-metastatické mutace, které se v nich díky selekčnímu tlaku hromadí, ale také „spolupracující“ nenádorové buňky z jejich okolí a jimi sekretované podpůrné faktory. Závěr: Současné pokroky ve výzkumu vedou k hlubšímu porozumění komplexních procesů vedoucích ke vzniku a šíření nádorových buněk. Poznání klíčových bodů metastatické kaskády a principy její regulace snad v budoucnu vyústí ve vývoj účinných chemoterapeutik cílených na metastazující buňky.

Background: Dissemination of cancer cells from the primary tumor and establishment of therapy-resistant distant metastases is the most common cause of human cancer deaths. The primary tumor consists of a heterogeneous population of cancer cells that have to overcome activity of the immune system, insufficient delivery of nutrients and oxygen, chemotherapy, radiotherapy etc. that lead to the selection of resistant and plastic cancer cells. Another selection pressure during metastatic spread gives rise to resistant subpopulations of cells, capable of surviving and proliferating in the hostile microenvironment of distant tissues. Aim: In this article, individual steps of the metastatic cascade are described as well as the mechanisms and signaling pathways that cancer cells use to deal with them. Metastatic process is generally inefficient and only very few cells released from the primary tumor develop into metastases. This success is enabled by pro-metastatic mutations, accumulated due to the selection pressure and also by cooperation of non-transformed cells that secrete supporting factors. Conclusion: Recent advances in research provide deeper insights into the complex processes that lead to formation and dissemination of cancer cells. Deciphering the key points of metastatic cascade and principles of its regulation will perhaps lead to development of efficient therapeutics targeting metastatic cells.

• MeSH
• buněčné mikroprostředí fyziologie   MeSH
• epitelo-mezenchymální tranzice MeSH
• karcinom komplikace   metabolismus   MeSH
• metastázy nádorů * patofyziologie   MeSH
• proliferace buněk fyziologie   MeSH
• receptory chemokinů klasifikace   metabolismus   MeSH
• tropismus fyziologie   MeSH
• vaskulární endoteliální růstový faktor A MeSH
• Publikační typ
• práce podpořená grantem MeSH
• přehledy MeSH

Plants adjust their growth according to gravity. Gravitropism involves gravity perception, signal transduction, and asymmetric growth response, with organ bending as a consequence [1]. Asymmetric growth results from the asymmetric distribution of the plant-specific signaling molecule auxin [2] that is generated by lateral transport, mediated in the hypocotyl predominantly by the auxin transporter PIN-FORMED3 (PIN3) [3-5]. Gravity stimulation polarizes PIN3 to the bottom sides of endodermal cells, correlating with increased auxin accumulation in adjacent tissues at the lower side of the stimulated organ, where auxin induces cell elongation and, hence, organ bending. A curvature response allows the hypocotyl to resume straight growth at a defined angle [6], implying that at some point auxin symmetry is restored to prevent overbending. Here, we present initial insights into cellular and molecular mechanisms that lead to the termination of the tropic response. We identified an auxin feedback on PIN3 polarization as underlying mechanism that restores symmetry of the PIN3-dependent auxin flow. Thus, two mechanistically distinct PIN3 polarization events redirect auxin fluxes at different time points of the gravity response: first, gravity-mediated redirection of PIN3-mediated auxin flow toward the lower hypocotyl side, where auxin gradually accumulates and promotes growth, and later PIN3 polarization to the opposite cell side, depleting this auxin maximum to end the bending. Accordingly, genetic or pharmacological interference with the late PIN3 polarization prevents termination of the response and leads to hypocotyl overbending. This observation reveals a role of auxin feedback on PIN polarity in the termination of the tropic response.

• MeSH
• Arabidopsis genetika   růst a vývoj   fyziologie   MeSH
• gravitropismus * MeSH
• kyseliny indoloctové metabolismus   MeSH
• percepce tíhy * MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• regulátory růstu rostlin metabolismus   MeSH
• výhonky rostlin růst a vývoj   MeSH
• zpětná vazba fyziologická MeSH
• Publikační typ
• časopisecké články MeSH

Redirection of intercellular auxin fluxes via relocalization of the PIN-FORMED 3 (PIN3) and PIN7 auxin efflux carriers has been suggested to be necessary for the root gravitropic response. Cytokinins have also been proposed to play a role in controlling root gravitropism, but conclusive evidence is lacking. We present a detailed study of the dynamics of root bending early after gravistimulation, which revealed a delayed gravitropic response in transgenic lines with depleted endogenous cytokinins (Pro35S:AtCKX) and cytokinin signaling mutants. Pro35S:AtCKX lines, as well as a cytokinin receptor mutant ahk3, showed aberrations in the auxin response distribution in columella cells consistent with defects in the auxin transport machinery. Using in vivo real-time imaging of PIN3-GFP and PIN7-GFP in AtCKX3 overexpression and ahk3 backgrounds, we observed wild-type-like relocalization of PIN proteins in the columella early after gravistimulation, with gravity-induced relocalization of PIN7 faster than that of PIN3. Nonetheless, the cellular distribution of PIN3 and PIN7 and expression of PIN7 and the auxin influx carrier AUX1 was affected in AtCKX overexpression lines. Based on the retained cytokinin sensitivity in pin3 pin4 pin7 mutant, we propose the AUX1-mediated auxin transport rather than columella-located PIN proteins as a target of endogenous cytokinins in the control of root gravitropism.

• MeSH
• Arabidopsis účinky léků   fyziologie   MeSH
• biologické modely MeSH
• biologický transport účinky léků   MeSH
• cytokininy farmakologie   MeSH
• gravitace MeSH
• gravitropismus účinky léků   MeSH
• kořeny rostlin účinky léků   fyziologie   MeSH
• kyseliny indoloctové metabolismus   MeSH
• meristém účinky léků   fyziologie   MeSH
• proteiny huseníčku metabolismus   MeSH
• signální transdukce účinky léků   MeSH
• zelené fluorescenční proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Infection caused by parasites from L. donovani complex can manifest as a serious visceral disease or a self-healing milder cutaneous form. The different tropism and pathology in humans is caused by the interaction between parasites, host and vector determinants but the mechanisms are not well understood. In Cukurova region in Turkey we previously identified a major focus of cutaneous leishmaniasis caused by L. donovani/infantum hybrids (CUK strain) and isolated this parasite from the locally abundant sand fly, Phlebotomus tobbi. Here, we present the first experimental study with P. tobbi. We tested the susceptibility of this species to various Leishmania under laboratory conditions, characterized glycoproteins in the P. tobbi midgut putatively involved in parasite-vector interaction and compared the development of the CUK strain in the sand fly with one other dermotropic and three viscerotropic strains belonging to the L. donovani complex. METHODS: Females of laboratory reared P. tobbi, P. perniciosus and Lutzomyia longipalpis were infected using membrane feeding on rabbit blood containing promastigotes of various Leishmania species with different tropisms. The individual guts were checked microscopically for presence and localization of Leishmania parasites; the number of parasites was assessed more precisely by qPCR. In addition, glycosylation of midgut proteins of P. tobbi was studied by lectin blotting of midgut lysate with lectins specific for terminal sugars of N-type and O-type glycans. RESULTS: High infection rates, heavy parasite loads and late-stage infection with colonization of the stomodeal valve were observed in P. tobbi infected by Leishmania major or L. infantum CUK hybrid. In parallel, lectin blotting revealed the presence of O-glycosylated proteins in the P. tobbi midgut. In P. perniciosus and L. longipalpis all five Leishmania strains tested developed well. In both vectors, significantly higher parasite numbers were detected by qPCR for dermotropic L. donovani from Cyprus, however, in all other parameters studied, including localization of infection and colonization of stomodeal valve, dermotropic and viscerotropic strains were not significantly different. CONCLUSIONS: We showed high susceptibility of P. tobbi to various Leishmania spp. This, together with the presence of O-glycosylated midgut proteins in their midguts demonstrate that P. tobbi is a permissive vector. Two dermotropic and three viscerotropic strains from the L. donovani complex developed late-stage infections in natural L. infantum vectors, P. perniciosus and L. longipalpis and none of the parameters studied seem to be linked with different tropism of parasites in the vertebrate host.

• MeSH
• gastrointestinální trakt parazitologie   MeSH
• hmyz - vektory parazitologie   MeSH
• králíci MeSH
• Leishmania infantum genetika   růst a vývoj   izolace a purifikace   MeSH
• Leishmania major genetika   růst a vývoj   izolace a purifikace   MeSH
• leishmanióza kožní epidemiologie   parazitologie   MeSH
• lidé MeSH
• Phlebotomus parazitologie   MeSH
• Psychodidae parazitologie   MeSH
• tropismus MeSH
• zvířata MeSH
• Check Tag
• králíci MeSH
• lidé MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Geografické názvy
• Turecko MeSH

BACKGROUND: The highly prevalent parasite Toxoplasma gondii reportedly manipulates rodent behavior to enhance the likelihood of transmission to its definitive cat host. The proximate mechanisms underlying this adaptive manipulation remain largely unclear, though a growing body of evidence suggests that the parasite-entrained dysregulation of dopamine metabolism plays a central role. Paradoxically, the distribution of the parasite in the brain has received only scant attention. METHODOLOGY/PRINCIPAL FINDINGS: The distributions of T. gondii cysts and histopathological lesions in the brains of CD1 mice with latent toxoplasmosis were analyzed using standard histological techniques. Mice were infected per orally with 10 tissue cysts of the avirulent HIF strain of T. gondii at six months of age and examined 18 weeks later. The cysts were distributed throughout the brain and selective tropism of the parasite toward a particular functional system was not observed. Importantly, the cysts were not preferentially associated with the dopaminergic system and absent from the hypothalamic defensive system. The striking interindividual differences in the total parasite load and cyst distribution indicate a probabilistic nature of brain infestation. Still, some brain regions were consistently more infected than others. These included the olfactory bulb, the entorhinal, somatosensory, motor and orbital, frontal association and visual cortices, and, importantly, the hippocampus and the amygdala. By contrast, a consistently low incidence of tissue cysts was recorded in the cerebellum, the pontine nuclei, the caudate putamen and virtually all compact masses of myelinated axons. Numerous perivascular and leptomeningeal infiltrations of inflammatory cells were observed, but they were not associated with intracellular cysts. CONCLUSION/SIGNIFICANCE: The observed pattern of T. gondii distribution stems from uneven brain colonization during acute infection and explains numerous behavioral abnormalities observed in the chronically infected rodents. Thus, the parasite can effectively change behavioral phenotype of infected hosts despite the absence of well targeted tropism.

• MeSH
• biologické modely MeSH
• chování zvířat MeSH
• chronická nemoc MeSH
• dopamin metabolismus   MeSH
• kočky MeSH
• kontrola chování MeSH
• mozek parazitologie   patologie   MeSH
• myši MeSH
• orgánová specificita MeSH
• počet buněk MeSH
• tělesná hmotnost fyziologie   MeSH
• Toxoplasma cytologie   fyziologie   MeSH
• toxoplazmóza parazitologie   patologie   MeSH
• tropismus fyziologie   MeSH
• velikost buňky MeSH
• zvířata MeSH
• Check Tag
• kočky MeSH
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH