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Special Issue "Auxins and Cytokinins in Plant Development"

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Plant Sciences".

Deadline for manuscript submissions: closed (31 January 2019)

Special Issue Editors

Guest Editor
Dr. Jan Petrášek

Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany of the Czech Academy of Sciences, Prague 6, Czech Republic
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Interests: plant development; plant hormones; cytoskeleton; advanced fluorescence microscopy
Guest Editor
Dr. Miroslav Kamínek

Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany of the Czech Academy of Sciences, Prague 6, Czech Republic
Website | E-Mail
Interests: hormonal regulation of plant development; cytokinin metabolism; cytokinin applications in plant biotechnology

Special Issue Information

Dear Colleagues,

Research of auxins and cytokinins, i.e., plant growth substances that play a central role in control of plant cell division and differentiation, is increasingly progressing, more than one hundred years since detection of their physiological manifestations in plants. It involves numerous other processes that attract attention from research, including plant responses to biotic and abiotic stimuli and exploitation of auxins and cytokinins in plant biotechnology. The Special Issue of IJMS, “Auxins and Cytokinins in Plant Development” is aimed to provide an up-to-date overview of the mechanisms of biosynthesis, metabolism, transport, signaling and developmental roles of both auxins and cytokinins. Within these mechanisms, we would like to emphasize those that integrate action of both auxins and cytokinins and, more importantly, modes of crosstalk with other plant hormones and environmental stimuli. This Special Issue will be released on the occasion of the symposium “Auxins and Cytokinins in Plant Development” in Prague, 1–5 July, 2018. Within the issue, we invite contributions from symposium participants; however, it is open to all other contributors.

Dr. Jan Petrášek
Dr. Miroslav Kamínek
Guest Editors

Manuscript Submission Information

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Keywords

  • auxin
  • cytokinin
  • plant development
  • plant hormone interactions
  • auxin-cytokinin crosstalk
  • auxin and cytokinin signalling networks
  • hormonal crosstalk

Published Papers (15 papers)

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Research

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Open AccessArticle Ontogenetic Changes in Auxin Biosynthesis and Distribution Determine the Organogenic Activity of the Shoot Apical Meristem in pin1 Mutants
Int. J. Mol. Sci. 2019, 20(1), 180; https://doi.org/10.3390/ijms20010180
Received: 19 November 2018 / Revised: 28 December 2018 / Accepted: 2 January 2019 / Published: 6 January 2019
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Abstract
In the shoot apical meristem (SAM) of Arabidopsis, PIN1-dependent polar auxin transport (PAT) regulates two crucial developmental processes: organogenesis and vascular system formation. However, the knockout mutation in the PIN1 gene does not fully inhibit these two processes. Therefore, we investigated a [...] Read more.
In the shoot apical meristem (SAM) of Arabidopsis, PIN1-dependent polar auxin transport (PAT) regulates two crucial developmental processes: organogenesis and vascular system formation. However, the knockout mutation in the PIN1 gene does not fully inhibit these two processes. Therefore, we investigated a potential source of auxin for organogenesis and vascularization during inflorescence stem development. We analyzed auxin distribution in wild-type (WT) and pin1 mutant plants using a refined protocol of auxin immunolocalization; auxin activity, with the response reporter pDR5:GFP; and expression of auxin biosynthesis genes YUC1 and YUC4. Our results revealed that regardless of the functionality of PIN1-mediated PAT, auxin is present in the SAM and vascular strands. In WT plants, auxin always accumulates in all cells of the SAM, whereas in pin1 mutants, its localization within the SAM changes ontogenetically and is related to changes in the structure of the vascular system, organogenic activity of SAM, and expression levels of YUC1 and YUC4 genes. Our findings indicate that the presence of auxin in the meristem of pin1 mutants is an outcome of at least two PIN1-independent mechanisms: acropetal auxin transport from differentiated tissues with the use of vascular strands and auxin biosynthesis within the SAM. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessArticle Supraoptimal Cytokinin Content Inhibits Rice Seminal Root Growth by Reducing Root Meristem Size and Cell Length via Increased Ethylene Content
Int. J. Mol. Sci. 2018, 19(12), 4051; https://doi.org/10.3390/ijms19124051
Received: 30 October 2018 / Revised: 30 November 2018 / Accepted: 12 December 2018 / Published: 14 December 2018
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Abstract
Cytokinins (CKs), a class of phytohormone, regulate root growth in a dose-dependent manner. A certain threshold content of CK is required for rapid root growth, but supraoptimal CK content inhibits root growth, and the mechanism of this inhibition remains unclear in rice. In [...] Read more.
Cytokinins (CKs), a class of phytohormone, regulate root growth in a dose-dependent manner. A certain threshold content of CK is required for rapid root growth, but supraoptimal CK content inhibits root growth, and the mechanism of this inhibition remains unclear in rice. In this study, treatments of lovastatin (an inhibitor of CK biosynthesis) and kinetin (KT; a synthetic CK) were found to inhibit rice seminal root growth in a dose-dependent manner, suggesting that endogenous CK content is optimal for rapid growth of the seminal root in rice. KT treatment strongly increased ethylene level by upregulating the transcription of ethylene biosynthesis genes. Ethylene produced in response to exogenous KT inhibited rice seminal root growth by reducing meristem size via upregulation of OsIAA3 transcription and reduced cell length by downregulating transcription of cell elongation-related genes. Moreover, the effects of KT treatment on rice seminal root growth, root meristem size and cell length were rescued by treatment with aminoethoxyvinylglycine (an inhibitor of ethylene biosynthesis), which restored ethylene level and transcription levels of OsIAA3 and cell elongation-related genes. Supraoptimal CK content increases ethylene level by promoting ethylene biosynthesis, which in turn inhibits rice seminal root growth by reducing root meristem size and cell length. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessArticle Hormonal Responses to Plasmodiophora brassicae Infection in Brassica napus Cultivars Differing in Their Pathogen Resistance
Int. J. Mol. Sci. 2018, 19(12), 4024; https://doi.org/10.3390/ijms19124024
Received: 15 November 2018 / Revised: 10 December 2018 / Accepted: 11 December 2018 / Published: 13 December 2018
Cited by 1 | PDF Full-text (3242 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Hormonal dynamics after Plasmodiophora brassicae infection were compared in two Brassica napus cultivars—more resistant SY Alister and more sensitive Hornet, in order to elucidate responses associated with efficient defense. Both cultivars responded to infection by the early transient elevation of active cytokinins (predominantly [...] Read more.
Hormonal dynamics after Plasmodiophora brassicae infection were compared in two Brassica napus cultivars—more resistant SY Alister and more sensitive Hornet, in order to elucidate responses associated with efficient defense. Both cultivars responded to infection by the early transient elevation of active cytokinins (predominantly cis-zeatin) and auxin indole-3-acetic acid (IAA) in leaves and roots, which was longer in Hornet. Moderate IAA levels in Hornet roots coincided with a high expression of biosynthetic gene nitrilase NIT1 (contrary to TAA1, YUC8, YUC9). Alister had a higher basal level of salicylic acid (SA), and it stimulated its production (via the expression of isochorismate synthase (ICS1)) in roots earlier than Hornet. Gall formation stimulated cytokinin, auxin, and SA levels—with a maximum 22 days after inoculation (dai). SA marker gene PR1 expression was the most profound at the time point where gall formation began, in leaves, roots, and especially in galls. Jasmonic acid (JA) was higher in Hornet than in Alister during the whole experiment. To investigate SA and JA function, SA was applied before infection, and twice (before infection and 15 dai), and JA at 15 dai. Double SA application diminished gall formation in Alister, and JA promoted gall formation in both cultivars. Activation of SA/JA pathways reflects the main differences in clubroot resistance. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessArticle Relative Contribution of PIN-Containing Secretory Vesicles and Plasma Membrane PINs to the Directed Auxin Transport: Theoretical Estimation
Int. J. Mol. Sci. 2018, 19(11), 3566; https://doi.org/10.3390/ijms19113566
Received: 17 September 2018 / Revised: 2 November 2018 / Accepted: 4 November 2018 / Published: 12 November 2018
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Abstract
The intercellular transport of auxin is driven by PIN-formed (PIN) auxin efflux carriers. PINs are localized at the plasma membrane (PM) and on constitutively recycling endomembrane vesicles. Therefore, PINs can mediate auxin transport either by direct translocation across the PM or by pumping [...] Read more.
The intercellular transport of auxin is driven by PIN-formed (PIN) auxin efflux carriers. PINs are localized at the plasma membrane (PM) and on constitutively recycling endomembrane vesicles. Therefore, PINs can mediate auxin transport either by direct translocation across the PM or by pumping auxin into secretory vesicles (SVs), leading to its secretory release upon fusion with the PM. Which of these two mechanisms dominates is a matter of debate. Here, we addressed the issue with a mathematical modeling approach. We demonstrate that the efficiency of secretory transport depends on SV size, half-life of PINs on the PM, pH, exocytosis frequency and PIN density. 3D structured illumination microscopy (SIM) was used to determine PIN density on the PM. Combining this data with published values of the other parameters, we show that the transport activity of PINs in SVs would have to be at least 1000× greater than on the PM in order to produce a comparable macroscopic auxin transport. If both transport mechanisms operated simultaneously and PINs were equally active on SVs and PM, the contribution of secretion to the total auxin flux would be negligible. In conclusion, while secretory vesicle-mediated transport of auxin is an intriguing and theoretically possible model, it is unlikely to be a major mechanism of auxin transport in planta. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessArticle Transcriptome Profiles Reveal the Crucial Roles of Auxin and Cytokinin in the “Shoot Branching” of Cremastra appendiculata
Int. J. Mol. Sci. 2018, 19(11), 3354; https://doi.org/10.3390/ijms19113354
Received: 23 August 2018 / Revised: 19 October 2018 / Accepted: 24 October 2018 / Published: 26 October 2018
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Abstract
Cremastra appendiculata has become endangered due to reproductive difficulties. Specifically, vegetative reproduction is almost its only way to reproduce, and, under natural conditions, it cannot grow branches, resulting in an extremely low reproductive coefficient (reproductive percentage). Here, we performed RNA-Seq and a differentially [...] Read more.
Cremastra appendiculata has become endangered due to reproductive difficulties. Specifically, vegetative reproduction is almost its only way to reproduce, and, under natural conditions, it cannot grow branches, resulting in an extremely low reproductive coefficient (reproductive percentage). Here, we performed RNA-Seq and a differentially expressed gene (DEG) analysis of the three stages of lateral bud development in C. appendiculata after decapitation—dormancy (D2), transition (TD2), and emergence (TG2)—and the annual axillary bud natural break (G1) to gain insight into the molecular regulatory network of shoot branching in this plant. Additionally, we applied the auxin transport inhibitors N-1-naphthylphthalamic acid (NPA) and 2,3,5-triiodibenzoic acid (TIBA) to a treated pseudobulb string of C. appendiculata to verify the conclusions obtained by the transcriptome. RNA-Seq provided a wealth of valuable information. Successive pairwise comparative transcriptome analyses revealed 5988 genes as DEGs. GO (Gene Ontology) and KEGG (Kyoto encyclopedia of genes and genomes) analyses of DEGs showed significant enrichments in phytohormone biosynthesis and metabolism, regulation of hormone levels, and a hormone-mediated signaling pathway. qRT-PCR validation showed a highly significant correlation (p < 0.01) with the RNA-Seq generated data. High-performance liquid chromatography (HPLC) and qRT-PCR results showed that, after decapitation, the NPA- and TIBA-induced lateral buds germinated due to rapidly decreasing auxin levels, caused by upregulation of the dioxygenase for auxin oxidation gene (DAO). Decreased auxin levels promoted the expression of isopentenyl transferase (IPT) and cytochrome P450 monooxygenase, family 735, subfamily A (CYP735A) genes and inhibited two carotenoid cleavage dioxygenases (CCD7 and CCD8). Zeatin levels significantly increased after the treatments. The increased cytokinin levels promoted the expression of WUSCHEL (WUS) and inhibited expression of BRANCHED1 (BRC1) in the cytokinin signal transduction pathway and initiated lateral bud outgrowth. Our data suggest that our theories concerning the regulation of shoot branching and apical dominance is really similar to those observed in annual plants. Auxin inhibits bud outgrowth and tends to inhibit cytokinin levels. The pseudobulb in the plant behaves in a similar manner to that of a shoot above the ground. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessArticle Correlations between Phytohormones and Drought Tolerance in Selected Brassica Crops: Chinese Cabbage, White Cabbage and Kale
Int. J. Mol. Sci. 2018, 19(10), 2866; https://doi.org/10.3390/ijms19102866
Received: 25 July 2018 / Revised: 11 September 2018 / Accepted: 12 September 2018 / Published: 21 September 2018
Cited by 4 | PDF Full-text (3265 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Drought is one of the major abiotic stresses affecting the productivity of Brassica crops. To understand the role of phytohormones in drought tolerance, we subjected Chinese cabbage (B. rapa ssp. pekinensis), white cabbage (B. oleracea var. capitata), and kale [...] Read more.
Drought is one of the major abiotic stresses affecting the productivity of Brassica crops. To understand the role of phytohormones in drought tolerance, we subjected Chinese cabbage (B. rapa ssp. pekinensis), white cabbage (B. oleracea var. capitata), and kale (B. oleracea var. acephala) to drought and examined the stress response on the physiological, biochemical and hormonal levels. The phytohormones abscisic acid (ABA), auxin indole-3-acetic acid (IAA), brassinosteroids (BRs), cytokinins (CKs), jasmonates (JAs), and salicylic acid (SA) were analyzed by ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). Based on the physiological and biochemical markers the Chinese cabbage exhibited the lowest tolerance, followed by the white cabbage, while the kale appeared to be the most tolerant to drought. The drought tolerance of the kale correlated with increased levels of SA, ABA, IAA, CKs iP(R) and cZ(R), and typhasterol (TY), a precursor of active BRs. In contrast, the drought sensitivity of the Chinese cabbage correlated with a significant increase in ABA, JAs and the active BRs castasterol (CS) and brassinolide (BL). The moderately tolerant white cabbage, positioned between the kale and Chinese cabbage, showed more similarity in terms of the phytohormone patterns with the kale. We concluded that the drought tolerance in Brassicaceae is mostly determined by the increased endogenous levels of IAA, CKs, ABA and SA and the decreased levels of active BRs. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Review

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Open AccessReview Molecular Communication for Coordinated Seed and Fruit Development: What Can We Learn from Auxin and Sugars?
Int. J. Mol. Sci. 2019, 20(4), 936; https://doi.org/10.3390/ijms20040936
Received: 30 January 2019 / Revised: 15 February 2019 / Accepted: 19 February 2019 / Published: 21 February 2019
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Abstract
Seed development in flowering plants is a critical part of plant life for successful reproduction. The formation of viable seeds requires the synchronous growth and development of the fruit and the three seed structures: the embryo, the endosperm, the seed coat. Molecular communication [...] Read more.
Seed development in flowering plants is a critical part of plant life for successful reproduction. The formation of viable seeds requires the synchronous growth and development of the fruit and the three seed structures: the embryo, the endosperm, the seed coat. Molecular communication between these tissues is crucial to coordinate these developmental processes. The phytohormone auxin is a significant player in embryo, seed and fruit development. Its regulated local biosynthesis and its cell-to-cell transport capacity make of auxin the perfect candidate as a signaling molecule to coordinate the growth and development of the embryo, endosperm, seed and fruit. Moreover, newly formed seeds need nutrients and form new carbon sink, generating high sugar flow from vegetative tissues to the seeds. This review will discuss how auxin and sugars may be considered as signaling molecules to coordinate seed and fruit development. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessReview Interplay of Auxin and Cytokinin in Lateral Root Development
Int. J. Mol. Sci. 2019, 20(3), 486; https://doi.org/10.3390/ijms20030486
Received: 18 December 2018 / Revised: 16 January 2019 / Accepted: 18 January 2019 / Published: 23 January 2019
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Abstract
The spacing and distribution of lateral roots are critical determinants of plant root system architecture. In addition to providing anchorage, lateral roots explore the soil to acquire water and nutrients. Over the past several decades, we have deepened our understanding of the regulatory [...] Read more.
The spacing and distribution of lateral roots are critical determinants of plant root system architecture. In addition to providing anchorage, lateral roots explore the soil to acquire water and nutrients. Over the past several decades, we have deepened our understanding of the regulatory mechanisms governing lateral root formation and development. In this review, we summarize these recent advances and provide an overview of how auxin and cytokinin coordinate the regulation of lateral root formation and development. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessReview Deciphering Auxin-Ethylene Crosstalk at a Systems Level
Int. J. Mol. Sci. 2018, 19(12), 4060; https://doi.org/10.3390/ijms19124060
Received: 13 November 2018 / Revised: 10 December 2018 / Accepted: 12 December 2018 / Published: 14 December 2018
Cited by 1 | PDF Full-text (1938 KB) | HTML Full-text | XML Full-text
Abstract
The auxin and ethylene pathways cooperatively regulate a variety of developmental processes in plants. Growth responses to ethylene are largely dependent on auxin, the key regulator of plant morphogenesis. Auxin, in turn, is capable of inducing ethylene biosynthesis and signaling, making the interaction [...] Read more.
The auxin and ethylene pathways cooperatively regulate a variety of developmental processes in plants. Growth responses to ethylene are largely dependent on auxin, the key regulator of plant morphogenesis. Auxin, in turn, is capable of inducing ethylene biosynthesis and signaling, making the interaction of these hormones reciprocal. Recent studies discovered a number of molecular events underlying auxin-ethylene crosstalk. In this review, we summarize the results of fine-scale and large-scale experiments on the interactions between the auxin and ethylene pathways in Arabidopsis. We integrate knowledge on molecular crosstalk events, their tissue specificity, and associated phenotypic responses to decipher the crosstalk mechanisms at a systems level. We also discuss the prospects of applying systems biology approaches to study the mechanisms of crosstalk between plant hormones. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessReview Multiple Links between HD-Zip Proteins and Hormone Networks
Int. J. Mol. Sci. 2018, 19(12), 4047; https://doi.org/10.3390/ijms19124047
Received: 31 October 2018 / Revised: 6 December 2018 / Accepted: 12 December 2018 / Published: 14 December 2018
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Abstract
HD-Zip proteins are unique to plants, and contain a homeodomain closely linked to a leucine zipper motif, which are involved in dimerization and DNA binding. Based on homology in the HD-Zip domain, gene structure and the presence of additional motifs, HD-Zips are divided [...] Read more.
HD-Zip proteins are unique to plants, and contain a homeodomain closely linked to a leucine zipper motif, which are involved in dimerization and DNA binding. Based on homology in the HD-Zip domain, gene structure and the presence of additional motifs, HD-Zips are divided into four families, HD-Zip I–IV. Phylogenetic analysis of HD-Zip genes using transcriptomic and genomic datasets from a wide range of plant species indicate that the HD-Zip protein class was already present in green algae. Later, HD-Zips experienced multiple duplication events that promoted neo- and sub-functionalizations. HD-Zip proteins are known to control key developmental and environmental responses, and a growing body of evidence indicates a strict link between members of the HD-Zip II and III families and the auxin machineries. Interactions of HD-Zip proteins with other hormones such as brassinolide and cytokinin have also been described. More recent data indicate that members of different HD-Zip families are directly involved in the regulation of abscisic acid (ABA) homeostasis and signaling. Considering the fundamental role of specific HD-Zip proteins in the control of key developmental pathways and in the cross-talk between auxin and cytokinin, a relevant role of these factors in adjusting plant growth and development to changing environment is emerging. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessReview Role of Cytokinins in Senescence, Antioxidant Defence and Photosynthesis
Int. J. Mol. Sci. 2018, 19(12), 4045; https://doi.org/10.3390/ijms19124045
Received: 24 October 2018 / Revised: 5 December 2018 / Accepted: 12 December 2018 / Published: 14 December 2018
Cited by 1 | PDF Full-text (576 KB) | HTML Full-text | XML Full-text
Abstract
Cytokinins modulate a number of important developmental processes, including the last phase of leaf development, known as senescence, which is associated with chlorophyll breakdown, photosynthetic apparatus disintegration and oxidative damage. There is ample evidence that cytokinins can slow down all these senescence-accompanying changes. [...] Read more.
Cytokinins modulate a number of important developmental processes, including the last phase of leaf development, known as senescence, which is associated with chlorophyll breakdown, photosynthetic apparatus disintegration and oxidative damage. There is ample evidence that cytokinins can slow down all these senescence-accompanying changes. Here, we review relationships between the various mechanisms of action of these regulatory molecules. We highlight their connection to photosynthesis, the pivotal process that generates assimilates, however may also lead to oxidative damage. Thus, we also focus on cytokinin induction of protective responses against oxidative damage. Activation of antioxidative enzymes in senescing tissues is described as well as changes in the levels of naturally occurring antioxidative compounds, such as phenolic acids and flavonoids, in plant explants. The main goal of this review is to show how the biological activities of cytokinins may be related to their chemical structure. New links between molecular aspects of natural cytokinins and their synthetic derivatives with antisenescent properties are described. Structural motifs in cytokinin molecules that may explain why these molecules play such a significant regulatory role are outlined. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessReview Auxin Controlled by Ethylene Steers Root Development
Int. J. Mol. Sci. 2018, 19(11), 3656; https://doi.org/10.3390/ijms19113656
Received: 8 October 2018 / Revised: 13 November 2018 / Accepted: 17 November 2018 / Published: 20 November 2018
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Abstract
Roots are important plant ground organs, which absorb water and nutrients to control plant growth and development. Phytohormones have been known to play a crucial role in the regulation of root growth, such as auxin and ethylene, which are central regulators of this [...] Read more.
Roots are important plant ground organs, which absorb water and nutrients to control plant growth and development. Phytohormones have been known to play a crucial role in the regulation of root growth, such as auxin and ethylene, which are central regulators of this process. Recent findings have revealed that root development and elongation regulated by ethylene are auxin dependent through alterations of auxin biosynthesis, transport and signaling. In this review, we focus on the recent advances in the study of auxin and auxin–ethylene crosstalk in plant root development, demonstrating that auxin and ethylene act synergistically to control primary root and root hair growth, but function antagonistically in lateral root formation. Moreover, ethylene modulates auxin biosynthesis, transport and signaling to fine-tune root growth and development. Thus, this review steps up the understanding of the regulation of auxin and ethylene in root growth. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessReview Advances in Understanding the Mechanism of Action of the Auxin Permease AUX1
Int. J. Mol. Sci. 2018, 19(11), 3391; https://doi.org/10.3390/ijms19113391
Received: 26 September 2018 / Revised: 19 October 2018 / Accepted: 24 October 2018 / Published: 30 October 2018
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Abstract
In over 40 years of research on the cellular uptake of auxin it is somewhat chastening that we have elaborated so little on the original kinetic descriptions of auxin uptake by plant cells made by Rubery and Sheldrake in 1974. Every aspect of [...] Read more.
In over 40 years of research on the cellular uptake of auxin it is somewhat chastening that we have elaborated so little on the original kinetic descriptions of auxin uptake by plant cells made by Rubery and Sheldrake in 1974. Every aspect of that seminal work has been investigated in detail, and the uptake activity they measured is now known to be attributed to the AUX1/LAX family of permeases. Recent pharmacological studies have defined the substrate specificity of AUX1, biochemical studies have evaluated its permeability to auxin in plant cell membranes, and rigourous kinetic studies have confirmed the affinity of AUX1 for IAA and synthetic auxins. Advances in genome sequencing have provided a rich resource for informatic analysis of the ancestry of AUX1 and the LAX proteins and, along with models of topology, suggest mechanistic links to families of eukaryotic proton co-transporters for which crystal structures have been presented. The insights gained from all the accumulated research reflect the brilliance of Rubery and Sheldrake’s early work, but recent biochemical analyses are starting to advance further our understanding of this vitally important family of auxin transport proteins. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Open AccessReview Auxins and Cytokinins—The Role of Subcellular Organization on Homeostasis
Int. J. Mol. Sci. 2018, 19(10), 3115; https://doi.org/10.3390/ijms19103115
Received: 12 September 2018 / Revised: 5 October 2018 / Accepted: 9 October 2018 / Published: 11 October 2018
Cited by 5 | PDF Full-text (2115 KB) | HTML Full-text | XML Full-text
Abstract
Plant hormones are master regulators of plant growth and development. Better knowledge of their spatial signaling and homeostasis (transport and metabolism) on the lowest structural levels (cellular and subcellular) is therefore crucial to a better understanding of developmental processes in plants. Recent progress [...] Read more.
Plant hormones are master regulators of plant growth and development. Better knowledge of their spatial signaling and homeostasis (transport and metabolism) on the lowest structural levels (cellular and subcellular) is therefore crucial to a better understanding of developmental processes in plants. Recent progress in phytohormone analysis at the cellular and subcellular levels has greatly improved the effectiveness of isolation protocols and the sensitivity of analytical methods. This review is mainly focused on homeostasis of two plant hormone groups, auxins and cytokinins. It will summarize and discuss their tissue- and cell-type specific distributions at the cellular and subcellular levels. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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Other

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Open AccessMeeting Report Auxins and Cytokinins in Plant Development 2018
Int. J. Mol. Sci. 2019, 20(4), 909; https://doi.org/10.3390/ijms20040909
Received: 15 February 2019 / Accepted: 18 February 2019 / Published: 20 February 2019
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Abstract
The international symposium “Auxins and Cytokinins in Plant Development” (ACPD), which is held every 4–5 years in Prague, Czech Republic, is a meeting of scientists interested in the elucidation of the action of two important plant hormones—auxins and cytokinins. It is organized by [...] Read more.
The international symposium “Auxins and Cytokinins in Plant Development” (ACPD), which is held every 4–5 years in Prague, Czech Republic, is a meeting of scientists interested in the elucidation of the action of two important plant hormones—auxins and cytokinins. It is organized by a group of researchers from the Laboratory of Hormonal Regulations in Plants at the Institute of Experimental Botany, the Czech Academy of Sciences. The symposia already have a long tradition, having started in 1972. Thanks to the central role of auxins and cytokinins in plant development, the ACPD 2018 symposium was again attended by numerous experts who presented their results in the opening, two plenary lectures, and six regular sessions, including two poster sessions. Due to the open character of the research community, which is traditionally very well displayed during the meeting, a lot of unpublished data were presented and discussed. In this report, we summarize the contributions in individual sessions that attracted our attention. Full article
(This article belongs to the Special Issue Auxins and Cytokinins in Plant Development)
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