International Journal of Molecular Sciences

Research

Jump to: Review

11 pages, 3748 KiB

Open AccessArticle

PIN7 Auxin Carrier Has a Preferential Role in Terminating Radial Root Expansion in Arabidopsis thaliana

by Michel Ruiz Rosquete, Sascha Waidmann and Jürgen Kleine-Vehn

Int. J. Mol. Sci. 2018, 19(4), 1238; https://doi.org/10.3390/ijms19041238 - 19 Apr 2018

Cited by 41 | Viewed by 7940

Abstract

Directional growth of lateral roots is critical for radial expansion and soil coverage. Despite its importance, almost nothing is known about its molecular determinants. Initially, young lateral roots (LRs) grow away from the parental root, maintaining the angle acquired shortly after emergence. A [...] Read more.

Directional growth of lateral roots is critical for radial expansion and soil coverage. Despite its importance, almost nothing is known about its molecular determinants. Initially, young lateral roots (LRs) grow away from the parental root, maintaining the angle acquired shortly after emergence. A second downwards bending response to gravity terminates the so-called plateau phase and thereby limits radial root expansion. Here, we show that the exit from the plateau phase correlates with an increase in auxin signalling at the tip of the LRs. Moreover, the increase in auxin levels induces the termination of the plateau phase, which requires PIN-FORMED (PIN) auxin efflux carriers. Our data suggests that the developmental increase in auxin triggers the preferential derepression of PIN7 in gravity-sensing columella cells. The subsequent polarization of PIN7 heralds the bending towards gravity and, hence, the exit from the plateau phase. This developmental framework reveals the distinct roles of PIN auxin efflux carriers in controlling the radial growth of root systems. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

15 pages, 2229 KiB

Open AccessArticle

Indole-3-Acetic Acid Biosynthesis Pathways in the Plant-Beneficial Bacterium Arthrobacter pascens ZZ21

by Mengsha Li, Rui Guo, Fei Yu, Xu Chen, Haiyan Zhao, Huixin Li and Jun Wu

Int. J. Mol. Sci. 2018, 19(2), 443; https://doi.org/10.3390/ijms19020443 - 1 Feb 2018

Cited by 86 | Viewed by 10545

Abstract

Arthrobacter pascens ZZ21 is a plant-beneficial, fluoranthene-degrading bacterial strain found in the rhizosphere. The production of the phytohormone indole-3-aectic acid (IAA) by ZZ21 is thought to contribute to its ability to promote plant growth and remediate fluoranthene-contaminated soil. Using genome-wide analysis combined with [...] Read more.

Arthrobacter pascens ZZ21 is a plant-beneficial, fluoranthene-degrading bacterial strain found in the rhizosphere. The production of the phytohormone indole-3-aectic acid (IAA) by ZZ21 is thought to contribute to its ability to promote plant growth and remediate fluoranthene-contaminated soil. Using genome-wide analysis combined with metabolomic and high-performance liquid chromatography-mass spectrometry (HPLC-MS) analyses, we characterized the potential IAA biosynthesis pathways in A. pascens ZZ21. IAA production increased 4.5-fold in the presence of 200 mg·L⁻¹ tryptophan in the culture medium. The transcript levels of prr and aldH, genes which were predicted to encode aldehyde dehydrogenases, were significantly upregulated in response to exogenous tryptophan. Additionally, metabolomic analysis identified the intermediates indole-3-acetamide (IAM), indole-3-pyruvic acid (IPyA), and the enzymatic reduction product of the latter, indole-3-lactic acid (ILA), among the metabolites of ZZ21, and subsequently also IAM, ILA, and indole-3-ethanol (TOL), which is the enzymatic reduction product of indole-3-acetaldehyde, by HPLC-MS. These results suggest that the tryptophan-dependent IAM and IPyA pathways function in ZZ21. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Figure 1

3408 KiB

Open AccessArticle

Identification and Expression Profiling of the Auxin Response Factors in Capsicum annuum L. under Abiotic Stress and Hormone Treatments

by Chenliang Yu, Yihua Zhan, Xuping Feng, Zong-An Huang and Chendong Sun

Int. J. Mol. Sci. 2017, 18(12), 2719; https://doi.org/10.3390/ijms18122719 - 15 Dec 2017

Cited by 22 | Viewed by 5172

Abstract

Auxin response factors (ARFs) play important roles in regulating plant growth and development and response to environmental stress. An exhaustive analysis of the CaARF family was performed using the latest publicly available genome for pepper (Capsicum annuum L.). In total, 22 non-redundant [...] Read more.

Auxin response factors (ARFs) play important roles in regulating plant growth and development and response to environmental stress. An exhaustive analysis of the CaARF family was performed using the latest publicly available genome for pepper (Capsicum annuum L.). In total, 22 non-redundant CaARF gene family members in six classes were analyzed, including chromosome locations, gene structures, conserved motifs of proteins, phylogenetic relationships and Subcellular localization. Phylogenetic analysis of the ARFs from pepper (Capsicum annuum L.), tomato (Solanum lycopersicum L.), Arabidopsis and rice (Oryza sativa L.) revealed both similarity and divergence between the four ARF families, and aided in predicting biological functions of the CaARFs. Furthermore, expression profiling of CaARFs was obtained in various organs and tissues using quantitative real-time RT-PCR (qRT-PCR). Expression analysis of these genes was also conducted with various hormones and abiotic treatments using qRT-PCR. Most CaARF genes were regulated by exogenous hormone treatments at the transcriptional level, and many CaARF genes were altered by abiotic stress. Systematic analysis of CaARF genes is imperative to elucidate the roles of CaARF family members in mediating auxin signaling in the adaptation of pepper to a challenging environment. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Figure 1

2909 KiB

Open AccessArticle

Nodule-Enriched GRETCHEN HAGEN 3 Enzymes Have Distinct Substrate Specificities and Are Important for Proper Soybean Nodule Development

by Suresh Damodaran, Corey S. Westfall, Brian A. Kisely, Joseph M. Jez and Senthil Subramanian

Int. J. Mol. Sci. 2017, 18(12), 2547; https://doi.org/10.3390/ijms18122547 - 28 Nov 2017

Cited by 13 | Viewed by 6238

Abstract

Legume root nodules develop as a result of a symbiotic relationship between the plant and nitrogen-fixing rhizobia bacteria in soil. Auxin activity is detected in different cell types at different stages of nodule development; as well as an enhanced sensitivity to auxin inhibits, [...] Read more.

Legume root nodules develop as a result of a symbiotic relationship between the plant and nitrogen-fixing rhizobia bacteria in soil. Auxin activity is detected in different cell types at different stages of nodule development; as well as an enhanced sensitivity to auxin inhibits, which could affect nodule development. While some transport and signaling mechanisms that achieve precise spatiotemporal auxin output are known, the role of auxin metabolism during nodule development is unclear. Using a soybean root lateral organ transcriptome data set, we identified distinct nodule enrichment of three genes encoding auxin-deactivating GRETCHEN HAGEN 3 (GH3) indole-3-acetic acid (IAA) amido transferase enzymes: GmGH3-11/12, GmGH3-14 and GmGH3-15. In vitro enzymatic assays showed that each of these GH3 proteins preferred IAA and aspartate as acyl and amino acid substrates, respectively. GmGH3-15 showed a broad substrate preference, especially with different forms of auxin. Promoter:GUS expression analysis indicated that GmGH3-14 acts primarily in the root epidermis and the nodule primordium where as GmGH3-15 might act in the vasculature. Silencing the expression of these GH3 genes in soybean composite plants led to altered nodule numbers, maturity, and size. Our results indicate that these GH3s are needed for proper nodule maturation in soybean, but the precise mechanism by which they regulate nodule development remains to be explained. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

8652 KiB

Open AccessArticle

Indole-3-Butyric Acid Induces Ectopic Formation of Metaxylem in the Hypocotyl of Arabidopsis thaliana without Conversion into Indole-3-Acetic Acid and with a Positive Interaction with Ethylene

by Laura Fattorini, Federica Della Rovere, Eleonora Andreini, Marilena Ronzan, Giuseppina Falasca and Maria Maddalena Altamura

Int. J. Mol. Sci. 2017, 18(11), 2474; https://doi.org/10.3390/ijms18112474 - 21 Nov 2017

Cited by 21 | Viewed by 5217

Abstract

The role of the auxins indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) and of the auxin-interacting phytohormone ethylene, on the ectopic formation of primary xylem (xylogenesis in planta) is still little known. In particular, auxin/ethylene-target tissue(s), modality of the xylary process (trans-differentiation vs. [...] Read more.

The role of the auxins indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) and of the auxin-interacting phytohormone ethylene, on the ectopic formation of primary xylem (xylogenesis in planta) is still little known. In particular, auxin/ethylene-target tissue(s), modality of the xylary process (trans-differentiation vs. de novo formation), and the kind of ectopic elements formed (metaxylem vs. protoxylem) are currently unknown. It is also unclear whether IBA may act on the process independently of conversion into IAA. To investigate these topics, histological analyses were carried out in the hypocotyls of Arabidopsis wild type seedlings and ech2ibr10 and ein3eil1 mutants, which are blocked in IBA-to-IAA conversion and ethylene signalling, respectively. The seedlings were grown under darkness with either IAA or IBA, combined or not with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid. Adventitious root formation was also investigated because this process may compete with xylogenesis. Our results show that ectopic formation of protoxylem and metaxylem occurred as an indirect process starting from the pericycle periclinal derivatives of the hypocotyl basal part. IAA favoured protoxylem formation, whereas IBA induced ectopic metaxylem with ethylene cooperation through the EIN3EIL1 network. Ectopic metaxylem differentiation occurred independently of IBA-to-IAA conversion as mediated by ECH2 and IBR10, and in the place of IBA-induced adventitious root formation. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

10330 KiB

Open AccessArticle

Two Paralogous Genes Encoding Auxin Efflux Carrier Differentially Expressed in Bitter Gourd (Momordica charantia)

by Yi-Li Li, Yun-Shan Lin, Pung-Ling Huang and Yi-Yin Do

Int. J. Mol. Sci. 2017, 18(11), 2343; https://doi.org/10.3390/ijms18112343 - 6 Nov 2017

Viewed by 4070

Abstract

The phytohormone auxin regulates various developmental programs in plants, including cell growth, cell division and cell differentiation. The auxin efflux carriers are essential for the auxin transport. To show an involvement of auxin transporters in the coordination of fruit development in bitter gourd, [...] Read more.

The phytohormone auxin regulates various developmental programs in plants, including cell growth, cell division and cell differentiation. The auxin efflux carriers are essential for the auxin transport. To show an involvement of auxin transporters in the coordination of fruit development in bitter gourd, a juicy fruit, we isolated novel cDNAs (referred as McPIN) encoding putative auxin efflux carriers, including McPIN1, McPIN2 (allele of McPIN1) and McPIN3, from developing fruits of bitter gourd. Both McPIN1 and McPIN3 genes possess six exons and five introns. Hydropathy analysis revealed that both polypeptides have two hydrophobic regions with five transmembrane segments and a predominantly hydrophilic core. Phylogenetic analyses revealed that McPIN1 shared the highest homology to the group of Arabidopsis, cucumber and tomato PIN1, while McPIN3 belonged to another group, including Arabidopsis and tomato PIN3 as well as PIN4. This suggests different roles for McPIN1 and McPIN3 in auxin transport involved in the fruit development of bitter gourd. Maximum mRNA levels for both genes were detected in staminate and pistillate flowers. McPIN1 is expressed in a particular period of early fruit development but McPIN3 continues to be expressed until the last stage of fruit ripening. Moreover, these two genes are auxin-inducible and qualified as early auxin-response genes. Their expression patterns suggest that these two auxin transporter genes play a pivotal role in fruit setting and development. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Figure 1

9180 KiB

Open AccessArticle

Evolutionary Conserved Cysteines Function as cis-Acting Regulators of Arabidopsis PIN-FORMED 2 Distribution

by Katarzyna Retzer, Jozef Lacek, Roman Skokan, Charo I. Del Genio, Stanislav Vosolsobě, Martina Laňková, Kateřina Malínská, Nataliia Konstantinova, Eva Zažímalová, Richard M. Napier, Jan Petrášek and Christian Luschnig

Int. J. Mol. Sci. 2017, 18(11), 2274; https://doi.org/10.3390/ijms18112274 - 29 Oct 2017

Cited by 27 | Viewed by 7627

Abstract

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 [...] Read more.

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 pin2^C−A alleles retained functionality, demonstrated by their ability to almost completely rescue defects of a pin2 null allele, whereas high resolution analysis of pin2^C−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. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

4529 KiB

Open AccessArticle

Evolution Analysis of the Aux/IAA Gene Family in Plants Shows Dual Origins and Variable Nuclear Localization Signals

by Wentao Wu, Yaxue Liu, Yuqian Wang, Huimin Li, Jiaxi Liu, Jiaxin Tan, Jiadai He, Jingwen Bai and Haoli Ma

Int. J. Mol. Sci. 2017, 18(10), 2107; https://doi.org/10.3390/ijms18102107 - 8 Oct 2017

Cited by 45 | Viewed by 7780 | Correction

Abstract

The plant hormone auxin plays pivotal roles in many aspects of plant growth and development. The auxin/indole-3-acetic acid (Aux/IAA) gene family encodes short-lived nuclear proteins acting on auxin perception and signaling, but the evolutionary history of this gene family remains to be elucidated. [...] Read more.

The plant hormone auxin plays pivotal roles in many aspects of plant growth and development. The auxin/indole-3-acetic acid (Aux/IAA) gene family encodes short-lived nuclear proteins acting on auxin perception and signaling, but the evolutionary history of this gene family remains to be elucidated. In this study, the Aux/IAA gene family in 17 plant species covering all major lineages of plants is identified and analyzed by using multiple bioinformatics methods. A total of 434 Aux/IAA genes was found among these plant species, and the gene copy number ranges from three (Physcomitrella patens) to 63 (Glycine max). The phylogenetic analysis shows that the canonical Aux/IAA proteins can be generally divided into five major clades, and the origin of Aux/IAA proteins could be traced back to the common ancestor of land plants and green algae. Many truncated Aux/IAA proteins were found, and some of these truncated Aux/IAA proteins may be generated from the C-terminal truncation of auxin response factor (ARF) proteins. Our results indicate that tandem and segmental duplications play dominant roles for the expansion of the Aux/IAA gene family mainly under purifying selection. The putative nuclear localization signals (NLSs) in Aux/IAA proteins are conservative, and two kinds of new primordial bipartite NLSs in P. patens and Selaginella moellendorffii were discovered. Our findings not only give insights into the origin and expansion of the Aux/IAA gene family, but also provide a basis for understanding their functions during the course of evolution. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Figure 1

4018 KiB

Open AccessArticle

Bioinformatics Analysis of Phylogeny and Transcription of TAA/YUC Auxin Biosynthetic Genes

by Axel Poulet and Verena Kriechbaumer

Int. J. Mol. Sci. 2017, 18(8), 1791; https://doi.org/10.3390/ijms18081791 - 18 Aug 2017

Cited by 41 | Viewed by 7714

Abstract

Auxin is a main plant growth hormone crucial in a multitude of developmental processes in plants. Auxin biosynthesis via the tryptophan aminotransferase of arabidopsis (TAA)/YUCCA (YUC) route involving tryptophan aminotransferases and YUC flavin-dependent monooxygenases that produce the auxin indole-3-acetic acid (IAA) from tryptophan [...] Read more.

Auxin is a main plant growth hormone crucial in a multitude of developmental processes in plants. Auxin biosynthesis via the tryptophan aminotransferase of arabidopsis (TAA)/YUCCA (YUC) route involving tryptophan aminotransferases and YUC flavin-dependent monooxygenases that produce the auxin indole-3-acetic acid (IAA) from tryptophan is currently the most researched auxin biosynthetic pathway. Previous data showed that, in maize and arabidopsis, TAA/YUC-dependent auxin biosynthesis can be detected in endoplasmic reticulum (ER) microsomal fractions, and a subset of auxin biosynthetic proteins are localized to the ER, mainly due to transmembrane domains (TMD). The phylogeny presented here for TAA/TAR (tryptophan aminotransferase related) and YUC proteins analyses phylogenetic groups as well as transmembrane domains for ER-membrane localisation. In addition, RNAseq datasets are analysed for transcript abundance of YUC and TAA/TAR proteins in Arabidopsis thaliana. We show that ER membrane localisation for TAA/YUC proteins involved in auxin biosynthesis is already present early on in the evolution of mosses and club mosses. ER membrane anchored YUC proteins can mainly be found in roots, while cytosolic proteins are more abundant in the shoot. The distribution between the different phylogenetic classes in root and shoot may well originate from gene duplications, and the phylogenetic groups detected also overlap with the biological function. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

Review

Jump to: Research

21 pages, 1555 KiB

Open AccessReview

The Role of Auxin in Cell Wall Expansion

by Mateusz Majda and Stéphanie Robert

Int. J. Mol. Sci. 2018, 19(4), 951; https://doi.org/10.3390/ijms19040951 - 22 Mar 2018

Cited by 280 | Viewed by 19948

Abstract

Plant cells are surrounded by cell walls, which are dynamic structures displaying a strictly regulated balance between rigidity and flexibility. Walls are fairly rigid to provide support and protection, but also extensible, to allow cell growth, which is triggered by a high intracellular [...] Read more.

Plant cells are surrounded by cell walls, which are dynamic structures displaying a strictly regulated balance between rigidity and flexibility. Walls are fairly rigid to provide support and protection, but also extensible, to allow cell growth, which is triggered by a high intracellular turgor pressure. Wall properties regulate the differential growth of the cell, resulting in a diversity of cell sizes and shapes. The plant hormone auxin is well known to stimulate cell elongation via increasing wall extensibility. Auxin participates in the regulation of cell wall properties by inducing wall loosening. Here, we review what is known on cell wall property regulation by auxin. We focus particularly on the auxin role during cell expansion linked directly to cell wall modifications. We also analyze downstream targets of transcriptional auxin signaling, which are related to the cell wall and could be linked to acid growth and the action of wall-loosening proteins. All together, this update elucidates the connection between hormonal signaling and cell wall synthesis and deposition. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

17 pages, 1859 KiB

Open AccessReview

Aux/IAA Gene Family in Plants: Molecular Structure, Regulation, and Function

by Jie Luo, Jing-Jing Zhou and Jin-Zhi Zhang

Int. J. Mol. Sci. 2018, 19(1), 259; https://doi.org/10.3390/ijms19010259 - 16 Jan 2018

Cited by 337 | Viewed by 23078

Abstract

Auxin plays a crucial role in the diverse cellular and developmental responses of plants across their lifespan. Plants can quickly sense and respond to changes in auxin levels, and these responses involve several major classes of auxin-responsive genes, including the Auxin/Indole-3-Acetic Acid ( [...] Read more.

Auxin plays a crucial role in the diverse cellular and developmental responses of plants across their lifespan. Plants can quickly sense and respond to changes in auxin levels, and these responses involve several major classes of auxin-responsive genes, including the Auxin/Indole-3-Acetic Acid (Aux/IAA) family, the auxin response factor (ARF) family, small auxin upregulated RNA (SAUR), and the auxin-responsive Gretchen Hagen3 (GH3) family. Aux/IAA proteins are short-lived nuclear proteins comprising several highly conserved domains that are encoded by the auxin early response gene family. These proteins have specific domains that interact with ARFs and inhibit the transcription of genes activated by ARFs. Molecular studies have revealed that Aux/IAA family members can form diverse dimers with ARFs to regulate genes in various ways. Functional analyses of Aux/IAA family members have indicated that they have various roles in plant development, such as root development, shoot growth, and fruit ripening. In this review, recently discovered details regarding the molecular characteristics, regulation, and protein–protein interactions of the Aux/IAA proteins are discussed. These details provide new insights into the molecular basis of the Aux/IAA protein functions in plant developmental processes. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Figure 1

6088 KiB

Open AccessReview

What Has Been Seen Cannot Be Unseen—Detecting Auxin In Vivo

by Barbora Pařízková, Markéta Pernisová and Ondřej Novák

Int. J. Mol. Sci. 2017, 18(12), 2736; https://doi.org/10.3390/ijms18122736 - 16 Dec 2017

Cited by 26 | Viewed by 12487

Abstract

Auxins mediate various processes that are involved in plant growth and development in response to specific environmental conditions. Its proper spatio-temporal distribution that is driven by polar auxin transport machinery plays a crucial role in the wide range of auxins physiological effects. Numbers [...] Read more.

Auxins mediate various processes that are involved in plant growth and development in response to specific environmental conditions. Its proper spatio-temporal distribution that is driven by polar auxin transport machinery plays a crucial role in the wide range of auxins physiological effects. Numbers of approaches have been developed to either directly or indirectly monitor auxin distribution in vivo in order to elucidate the basis of its precise regulation. Herein, we provide an updated list of valuable techniques used for monitoring auxins in plants, with their utilities and limitations. Because the spatial and temporal resolutions of the presented approaches are different, their combination may provide a comprehensive outcome of auxin distribution in diverse developmental processes. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

899 KiB

Open AccessReview

Control of Endogenous Auxin Levels in Plant Root Development

by Damilola Olatunji, Danny Geelen and Inge Verstraeten

Int. J. Mol. Sci. 2017, 18(12), 2587; https://doi.org/10.3390/ijms18122587 - 1 Dec 2017

Cited by 134 | Viewed by 13929

Abstract

In this review, we summarize the different biosynthesis-related pathways that contribute to the regulation of endogenous auxin in plants. We demonstrate that all known genes involved in auxin biosynthesis also have a role in root formation, from the initiation of a root meristem [...] Read more.

In this review, we summarize the different biosynthesis-related pathways that contribute to the regulation of endogenous auxin in plants. We demonstrate that all known genes involved in auxin biosynthesis also have a role in root formation, from the initiation of a root meristem during embryogenesis to the generation of a functional root system with a primary root, secondary lateral root branches and adventitious roots. Furthermore, the versatile adaptation of root development in response to environmental challenges is mediated by both local and distant control of auxin biosynthesis. In conclusion, auxin homeostasis mediated by spatial and temporal regulation of auxin biosynthesis plays a central role in determining root architecture. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

1718 KiB

Open AccessReview

Auxin Information Processing; Partners and Interactions beyond the Usual Suspects

by Thea Van den Berg and Kirsten H. Ten Tusscher

Int. J. Mol. Sci. 2017, 18(12), 2585; https://doi.org/10.3390/ijms18122585 - 1 Dec 2017

Cited by 7 | Viewed by 4942

Abstract

Auxin plays a major role in a variety of processes involved in plant developmental patterning and its adaptation to environmental conditions. Therefore, an important question is how specificity in auxin signalling is achieved, that is, how a single signalling molecule can carry so [...] Read more.

Auxin plays a major role in a variety of processes involved in plant developmental patterning and its adaptation to environmental conditions. Therefore, an important question is how specificity in auxin signalling is achieved, that is, how a single signalling molecule can carry so many different types of information. In recent years, many studies on auxin specificity have been published, unravelling increasingly more details on differential auxin sensitivity, expression domains and downstream partners of the auxin receptors (transport inhibitor response 1 (TIR1) and other auxin signaling F-box proteins (AFB)), transcriptional repressors that are degraded in response to auxin (AUX/IAA) and downstream auxin response factors (ARF) that together constitute the plant’s major auxin response pathways. These data are critical to explain how, in the same cells, different auxin levels may trigger different responses, as well as how in different spatial or temporal contexts similar auxin signals converge to different responses. However, these insights do not yet answer more complex questions regarding auxin specificity. As an example, they leave open the question of how similar sized auxin changes at similar locations result in different responses depending on the duration and spatial extent of the fluctuation in auxin levels. Similarly, it leaves unanswered how, in the case of certain tropisms, small differences in signal strength at both sides of a plant organ are converted into an instructive auxin asymmetry that enables a robust tropic response. Finally, it does not explain how, in certain cases, substantially different auxin levels become translated into similar cellular responses, while in other cases similar auxin levels, even when combined with similar auxin response machinery, may trigger different responses. In this review, we illustrate how considering the regulatory networks and contexts in which auxin signalling takes place helps answer these types of fundamental questions. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Figure 1

9891 KiB

Open AccessReview

Plants under Stress: Involvement of Auxin and Cytokinin

by Agnieszka Bielach, Monika Hrtyan and Vanesa B. Tognetti

Int. J. Mol. Sci. 2017, 18(7), 1427; https://doi.org/10.3390/ijms18071427 - 4 Jul 2017

Cited by 254 | Viewed by 17753

Abstract

Plant growth and development are critically influenced by unpredictable abiotic factors. To survive fluctuating changes in their environments, plants have had to develop robust adaptive mechanisms. The dynamic and complementary actions of the auxin and cytokinin pathways regulate a plethora of developmental processes, [...] Read more.

Plant growth and development are critically influenced by unpredictable abiotic factors. To survive fluctuating changes in their environments, plants have had to develop robust adaptive mechanisms. The dynamic and complementary actions of the auxin and cytokinin pathways regulate a plethora of developmental processes, and their ability to crosstalk makes them ideal candidates for mediating stress-adaptation responses. Other crucial signaling molecules responsible for the tremendous plasticity observed in plant morphology and in response to abiotic stress are reactive oxygen species (ROS). Proper temporal and spatial distribution of ROS and hormone gradients is crucial for plant survival in response to unfavorable environments. In this regard, the convergence of ROS with phytohormone pathways acts as an integrator of external and developmental signals into systemic responses organized to adapt plants to their environments. Auxin and cytokinin signaling pathways have been studied extensively. Nevertheless, we do not yet understand the impact on plant stress tolerance of the sophisticated crosstalk between the two hormones. Here, we review current knowledge on the function of auxin and cytokinin in redirecting growth induced by abiotic stress in order to deduce their potential points of crosstalk. Full article

(This article belongs to the Special Issue Auxin)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Auxin

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (15 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI