Apple species are the unique naturally rich source of dihydrochalcones, phenolic compounds with an elusive role in planta, but suggested auto-allelochemical features related to "apple replant disease" (ARD). Our aim was to elucidate the physiological basis of the phytotoxic action of dihydrochalcone phloretin in the model plant Arabidopsis and to promote phloretin as a new prospective eco-friendly phytotoxic compound. Phloretin treatment induced a significant dose-dependent growth retardation and severe morphological abnormalities and agravitropic behavior in Arabidopsis seedlings. Histological examination revealed a reduced starch content in the columella cells and a serious disturbance in root architecture, which resulted in the reduction in length of meristematic and elongation zones. Significantly disturbed auxin metabolome profile in roots with a particularly increased content of IAA accumulated in the lateral parts of the root apex, accompanied by changes in the expression of auxin biosynthetic and transport genes, especially PIN1, PIN3, PIN7, and ABCB1, indicates the role of auxin in physiological basis of phloretin-induced growth retardation. The results reveal a disturbance of auxin homeostasis as the main mechanism of phytotoxic action of phloretin. This mechanism makes phloretin a prospective candidate for an eco-friendly bioherbicide and paves the way for further research of phloretin role in ARD.

• Klíčová slova
• ARD, Malus × domestica Borkh. (apple), allelopathy, auxin, dihydrochalcones, phloretin, phytotoxicity, polar auxin transport,
• Publikační typ
• časopisecké články MeSH

Directional root growth control is crucial for plant fitness. The degree of root growth deviation depends on several factors, whereby exogenous growth conditions have a profound impact. The perception of mechanical impedance by wild-type roots results in the modulation of root growth traits, and it is known that gravitropic stimulus influences distinct root movement patterns in concert with mechanoadaptation. Mutants with reduced shootward auxin transport are described as being numb towards mechanostimulus and gravistimulus, whereby different growth conditions on agar-supplemented medium have a profound effect on how much directional root growth and root movement patterns differ between wild types and mutants. To reduce the impact of unilateral mechanostimulus on roots grown along agar-supplemented medium, we compared the root movement of Col-0 and auxin resistant 1-7 in a root penetration assay to test how both lines adjust the growth patterns of evenly mechanostimulated roots. We combined the assay with the D-root system to reduce light-induced growth deviation. Moreover, the impact of sucrose supplementation in the growth medium was investigated because exogenous sugar enhances root growth deviation in the vertical direction. Overall, we observed a more regular growth pattern for Col-0 but evaluated a higher level of skewing of aux1-7 compared to the wild type than known from published data. Finally, the tracking of the growth rate of the gravistimulated roots revealed that Col-0 has a throttling elongation rate during the bending process, but aux1-7 does not.

• Klíčová slova
• AUX1, AUXIN-RESISTANT 1, D-root system, directional root growth, gravitropic response, mechanoadaptation, mechanostimulus, root elongation rate, root penetration assay, root skewing,
• Publikační typ
• časopisecké články MeSH

Size control is a fundamental question in biology, showing incremental complexity in plants, whose cells possess a rigid cell wall. The phytohormone auxin is a vital growth regulator with central importance for differential growth control. Our results indicate that auxin-reliant growth programs affect the molecular complexity of xyloglucans, the major type of cell wall hemicellulose in eudicots. Auxin-dependent induction and repression of growth coincide with reduced and enhanced molecular complexity of xyloglucans, respectively. In agreement with a proposed function in growth control, genetic interference with xyloglucan side decorations distinctly modulates auxin-dependent differential growth rates. Our work proposes that auxin-dependent growth programs have a spatially defined effect on xyloglucan's molecular structure, which in turn affects cell wall mechanics and specifies differential, gravitropic hypocotyl growth.

• Klíčová slova
• auxin, cell wall, gravitropism, growth, hypocotyls, xyloglucans,
• MeSH
• Arabidopsis fyziologie   MeSH
• buněčná stěna metabolismus   MeSH
• fluorescenční protilátková technika MeSH
• fyziologie rostlin * MeSH
• glukany chemie   metabolismus   MeSH
• hrách setý fyziologie   MeSH
• kyseliny indoloctové metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné buňky metabolismus   MeSH
• signální transdukce MeSH
• vývoj rostlin * MeSH
• xylany chemie   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• glukany MeSH
• kyseliny indoloctové MeSH
• xylany MeSH
• xyloglucan MeSH Prohlížeč

Plant roots are very plastic and can adjust their tissue organization and cell appearance during abiotic stress responses. Previous studies showed that direct root illumination and sugar supplementation mask root growth phenotypes and traits. Sugar and light signaling where further connected to changes in auxin biosynthesis and distribution along the root. Auxin signaling underpins almost all processes involved in the establishment of root traits, including total root length, gravitropic growth, root hair initiation and elongation. Root hair plasticity allows maximized nutrient uptake and therefore plant productivity, and root hair priming and elongation require proper auxin availability. In the presence of sucrose in the growth medium, root hair emergence is partially rescued, but the full potential of root hair elongation is lost. With our work we describe a combinatory study showing to which extent light and sucrose are antagonistically influencing root length, but additively affecting root hair emergence and elongation. Furthermore, we investigated the impact of the loss of PIN-FORMED2, an auxin efflux carrier mediating shootward auxin transporter, on the establishment of root traits in combination with all growth conditions.

• Klíčová slova
• PIN-FORMED2, dark grown roots, gravitropic index, light grown roots, root growth, root hair, root hair elongation, shootward auxin transport, sucrose, sugar, total root length,
• Publikační typ
• časopisecké články MeSH

Cell polarity is a fundamental feature of all multicellular organisms. PIN auxin transporters are important cell polarity markers that play crucial roles in a plethora of developmental processes in plants. Here, to identify components involved in cell polarity establishment and maintenance in plants, we performed a forward genetic screening of PIN2:PIN1-HA;pin2 Arabidopsis (Arabidopsis thaliana) plants, which ectopically express predominantly basally localized PIN1 in root epidermal cells, leading to agravitropic root growth. We identified the regulator of PIN polarity 12 (repp12) mutation, which restored gravitropic root growth and caused a switch in PIN1-HA polarity from the basal to apical side of root epidermal cells. Next Generation Sequencing and complementation experiments established the causative mutation of repp12 as a single amino acid exchange in Aminophospholipid ATPase3 (ALA3), a phospholipid flippase predicted to function in vesicle formation. repp12 and ala3 T-DNA mutants show defects in many auxin-regulated processes, asymmetric auxin distribution, and PIN trafficking. Analysis of quintuple and sextuple mutants confirmed the crucial roles of ALA proteins in regulating plant development as well as PIN trafficking and polarity. Genetic and physical interaction studies revealed that ALA3 functions together with the ADP ribosylation factor GTPase exchange factors GNOM and BIG3 in regulating PIN polarity, trafficking, and auxin-mediated development.

• MeSH
• ADP-ribosylační faktory metabolismus   MeSH
• Arabidopsis účinky léků   metabolismus   MeSH
• biologický transport účinky léků   MeSH
• brefeldin A farmakologie   MeSH
• buněčná membrána účinky léků   metabolismus   MeSH
• genetická epistáze účinky léků   MeSH
• GTP-fosfohydrolasy metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• mutace genetika   MeSH
• proteiny huseníčku metabolismus   MeSH
• proteiny přenášející fosfolipidy metabolismus   MeSH
• tabák metabolismus   MeSH
• trans-Golgiho síť účinky léků   metabolismus   MeSH
• vazba proteinů účinky léků   MeSH
• výměnné faktory guaninnukleotidů metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ADP-ribosylační faktory MeSH
• brefeldin A MeSH
• GTP-fosfohydrolasy MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH
• proteiny přenášející fosfolipidy MeSH
• výměnné faktory guaninnukleotidů MeSH

Cell polarity, manifested by the localization of proteins to distinct polar plasma membrane domains, is a key prerequisite of multicellular life. In plants, PIN auxin transporters are prominent polarity markers crucial for a plethora of developmental processes. Cell polarity mechanisms in plants are distinct from other eukaryotes and still largely elusive. In particular, how the cell polarities are propagated and maintained following cell division remains unknown. Plant cytokinesis is orchestrated by the cell plate-a transient centrifugally growing endomembrane compartment ultimately forming the cross wall1. Trafficking of polar membrane proteins is typically redirected to the cell plate, and these will consequently have opposite polarity in at least one of the daughter cells2-5. Here, we provide mechanistic insights into post-cytokinetic re-establishment of cell polarity as manifested by the apical, polar localization of PIN2. We show that the apical domain is defined in a cell-intrinsic manner and that re-establishment of PIN2 localization to this domain requires de novo protein secretion and endocytosis, but not basal-to-apical transcytosis. Furthermore, we identify a PINOID-related kinase WAG1, which phosphorylates PIN2 in vitro6 and is transcriptionally upregulated specifically in dividing cells, as a crucial regulator of post-cytokinetic PIN2 polarity re-establishment.

• MeSH
• Arabidopsis cytologie   genetika   fyziologie   MeSH
• buněčná membrána metabolismus   MeSH
• buněčné dělení * MeSH
• cytokineze MeSH
• endocytóza MeSH
• fenotyp MeSH
• fosforylace MeSH
• kořeny rostlin cytologie   genetika   fyziologie   MeSH
• polarita buněk * MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• rekombinantní fúzní proteiny MeSH
• reportérové geny MeSH
• transport proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• PIN2 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku MeSH
• rekombinantní fúzní proteiny MeSH

Coordination of plant development requires modulation of growth responses that are under control of the phytohormone auxin. PIN-FORMED plasma membrane proteins, involved in intercellular transport of the growth regulator, are key to the transmission of such auxin signals and subject to multilevel surveillance mechanisms, including reversible post-translational modifications. Apart from well-studied PIN protein modifications, namely phosphorylation and ubiquitylation, no further post-translational modifications have been described so far. Here, we focused on root-specific Arabidopsis PIN2 and explored functional implications of two evolutionary conserved cysteines, by a combination of in silico and molecular approaches. PIN2 sequence alignments and modeling predictions indicated that both cysteines are facing the cytoplasm and therefore would be accessible to redox status-controlled modifications. Notably, mutant pin2C-A alleles retained functionality, demonstrated by their ability to almost completely rescue defects of a pin2 null allele, whereas high resolution analysis of pin2C-A localization revealed increased intracellular accumulation, and altered protein distribution within plasma membrane micro-domains. The observed effects of cysteine replacements on root growth and PIN2 localization are consistent with a model in which redox status-dependent cysteine modifications participate in the regulation of PIN2 mobility, thereby fine-tuning polar auxin transport.

• Klíčová slova
• Arabidopsis, Auxin, PIN proteins, SRRF, intracellular distribution, plasma membrane protein sorting, protein mobility, protein modeling, root phenotype,
• MeSH
• Arabidopsis genetika   metabolismus   MeSH
• cystein genetika   MeSH
• konzervovaná sekvence * MeSH
• kořeny rostlin růst a vývoj   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• membránové mikrodomény metabolismus   MeSH
• proteiny huseníčku chemie   genetika   metabolismus   MeSH
• transport proteinů MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cystein MeSH
• kyseliny indoloctové MeSH
• PIN2 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku MeSH

N6-adenosine methylation (m6 A) of mRNA is an essential process in most eukaryotes, but its role and the status of factors accompanying this modification are still poorly understood. Using combined methods of genetics, proteomics and RNA biochemistry, we identified a core set of mRNA m6 A writer proteins in Arabidopsis thaliana. The components required for m6 A in Arabidopsis included MTA, MTB, FIP37, VIRILIZER and the E3 ubiquitin ligase HAKAI. Downregulation of these proteins led to reduced relative m6 A levels and shared pleiotropic phenotypes, which included aberrant vascular formation in the root, indicating that correct m6 A methylation plays a role in developmental decisions during pattern formation. The conservation of these proteins amongst eukaryotes and the demonstration of a role in writing m6 A for the E3 ubiquitin ligase HAKAI is likely to be of considerable relevance beyond the plant sciences.

• Klíčová slova
• Arabidopsis, HAKAI, N6-adenosine methylation (m6A), VIRILIZER, mRNA methylation, protoxylem,
• MeSH
• adenosin metabolismus   MeSH
• Arabidopsis metabolismus   MeSH
• geneticky modifikované rostliny metabolismus   MeSH
• konzervovaná sekvence MeSH
• messenger RNA metabolismus   MeSH
• methyltransferasy genetika   metabolismus   fyziologie   MeSH
• metylace MeSH
• proteiny huseníčku genetika   metabolismus   fyziologie   MeSH
• sekvenční seřazení MeSH
• ubikvitinligasy genetika   metabolismus   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 6-methyladenine mRNA methyltransferase MeSH Prohlížeč
• adenosin MeSH
• messenger RNA MeSH
• methyltransferasy MeSH
• proteiny huseníčku MeSH
• ubikvitinligasy MeSH

The phytohormone auxin is a major determinant and regulatory component important for plant development. Auxin transport between cells is mediated by a complex system of transporters such as AUX1/LAX, PIN, and ABCB proteins, and their localization and activity is thought to be influenced by phosphatases and kinases. Flavonols have been shown to alter auxin transport activity and changes in flavonol accumulation in the Arabidopsis thaliana rol1-2 mutant cause defects in auxin transport and seedling development. A new mutation in ROOTS CURL IN NPA 1 (RCN1), encoding a regulatory subunit of the phosphatase PP2A, was found to suppress the growth defects of rol1-2 without changing the flavonol content. rol1-2 rcn1-3 double mutants show wild type-like auxin transport activity while levels of free auxin are not affected by rcn1-3. In the rol1-2 mutant, PIN2 shows a flavonol-induced basal-to-apical shift in polar localization which is reversed in the rol1-2 rcn1-3 to basal localization. In vivo analysis of PINOID action, a kinase known to influence PIN protein localization in a PP2A-antagonistic manner, revealed a negative impact of flavonols on PINOID activity. Together, these data suggest that flavonols affect auxin transport by modifying the antagonistic kinase/phosphatase equilibrium.

• MeSH
• Arabidopsis účinky léků   genetika   metabolismus   MeSH
• flavonoidy farmakologie   MeSH
• glukosyltransferasy genetika   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• mutace MeSH
• proteinfosfatasa 2 genetika   metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 3-hydroxyflavone MeSH Prohlížeč
• flavonoidy MeSH
• glukosyltransferasy MeSH
• kyseliny indoloctové MeSH
• PIN2 protein, Arabidopsis MeSH Prohlížeč
• proteinfosfatasa 2 MeSH
• proteiny huseníčku MeSH
• RCN1 protein, Arabidopsis MeSH Prohlížeč
• RHM1 protein, Arabidopsis MeSH Prohlížeč