scholarly journals Auxin requirements for a meristematic state in roots depend on a dual brassinosteroid function

2020 ◽  
Author(s):  
M. Ackerman-Lavert ◽  
Y. Fridman ◽  
R Matosevich ◽  
H Khandal ◽  
L. Friedlander ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Auxin Biosynthesis ◽  
Auxin Signaling ◽  
Critical Ratio ◽  
Dual Effect ◽  
Normal Morphology ◽  
Arabidopsis Root ◽  
Auxin Synthesis ◽  
Meristem Maintenance ◽  
Transcriptional Output

SummaryThe organization of the root meristem is maintained by a complex interplay between plant hormones signaling pathways that both interpret and determine their accumulation and distribution. Brassinosteroids (BR) and auxin signaling pathways control the number of meristematic cells in the Arabidopsis root, via an interaction that appears to involve contradicting molecular outcomes, with BR promoting auxin signaling input but also repressing its output. However, whether this seemingly incoherent effect is significant for meristem function is unclear. Here, we established that a dual effect of BR on auxin, with BR simultaneously promoting auxin biosynthesis and repressing auxin transcriptional output, is essential for meristem maintenance. Blocking BR-induced auxin synthesis resulted in rapid BR-mediated meristem loss. Conversely, plants with reduced BR levels were resistant to loss of auxin biosynthesis and these meristems maintained their normal morphology despite a 10-fold decrease in auxin levels. In agreement, injured root meristems which rely solely on local auxin synthesis, regenerated when both auxin and BR synthesis were inhibited. Use of BIN2 as a tool to selectively inhibit BR signaling, revealed meristems with distinct phenotypes depending on the perturbed tissue; meristem reminiscent of BR-deficient mutants or of high BR exposure. This enabled mapping BR-auxin interactions to the outer epidermis and lateral root cap tissues, and demonstrated the essentiality of BR signaling in these tissues for meristem maintenance. BR activity in internal tissues however, proved necessary to control BR homeostasis. Together, we demonstrate a basis for inter-tissue coordination and how a critical ratio between these hormones determines the meristematic state.

scholarly journals Membrane Sterol Composition in Arabidopsis thaliana Affects Root Elongation via Auxin Biosynthesis

2021 ◽  
Vol 22 (1) ◽  
pp. 437
Author(s):  
Meng Wang ◽  
Panpan Li ◽  
Yao Ma ◽  
Xiang Nie ◽  
Markus Grebe ◽  
...  
Keyword(s):  
Root Elongation ◽  
Auxin Transport ◽  
Sterol Composition ◽  
Polar Auxin Transport ◽  
Sterol Biosynthesis ◽  
Auxin Biosynthesis ◽  
Root Tip ◽  
Auxin Signaling ◽  
Auxin Response ◽  
Short Root

Plant membrane sterol composition has been reported to affect growth and gravitropism via polar auxin transport and auxin signaling. However, as to whether sterols influence auxin biosynthesis has received little attention. Here, by using the sterol biosynthesis mutant cyclopropylsterol isomerase1-1 (cpi1-1) and sterol application, we reveal that cycloeucalenol, a CPI1 substrate, and sitosterol, an end-product of sterol biosynthesis, antagonistically affect auxin biosynthesis. The short root phenotype of cpi1-1 was associated with a markedly enhanced auxin response in the root tip. Both were neither suppressed by mutations in polar auxin transport (PAT) proteins nor by treatment with a PAT inhibitor and responded to an auxin signaling inhibitor. However, expression of several auxin biosynthesis genes TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1 (TAA1) was upregulated in cpi1-1. Functionally, TAA1 mutation reduced the auxin response in cpi1-1 and partially rescued its short root phenotype. In support of this genetic evidence, application of cycloeucalenol upregulated expression of the auxin responsive reporter DR5:GUS (β-glucuronidase) and of several auxin biosynthesis genes, while sitosterol repressed their expression. Hence, our combined genetic, pharmacological, and sterol application studies reveal a hitherto unexplored sterol-dependent modulation of auxin biosynthesis during Arabidopsis root elongation.

scholarly journals Protoplast Swelling and Hypocotyl Growth Depend on Different Auxin Signaling Pathways

2017 ◽  
Vol 175 (2) ◽  
pp. 982-994 ◽  
Author(s):  
Renate I. Dahlke ◽  
Simon Fraas ◽  
Kristian K. Ullrich ◽  
Kirka Heinemann ◽  
Maren Romeiks ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Auxin Signaling ◽  
Hypocotyl Growth

scholarly journals PIF4-controlled auxin pathway contributes to hybrid vigor in Arabidopsis thaliana

2017 ◽  
Vol 114 (17) ◽  
pp. E3555-E3562 ◽  
Author(s):  
Li Wang ◽  
Li Min Wu ◽  
Ian K. Greaves ◽  
Anyu Zhu ◽  
Elizabeth S. Dennis ◽  
...  
Keyword(s):  
Recurrent Selection ◽  
Leaf Growth ◽  
Hybrid Vigor ◽  
Auxin Biosynthesis ◽  
F1 Hybrids ◽  
Auxin Signaling ◽  
Crop Species ◽  
Altered Expression ◽  
F2 Generation ◽  
Chromosome Segments

F1 hybrids in Arabidopsis and crop species are uniform and high yielding. The F2 generation loses much of the yield advantage and the plants have heterogeneous phenotypes. We generated pure breeding hybrid mimic lines by recurrent selection and also selected a pure breeding small phenotype line. The hybrid mimics are almost completely homozygous with chromosome segments from each parent. Four particular chromosomal segments from C24 and 8 from Ler were present in all of the hybrid mimic lines, whereas in the F6 small phenotype line, the 12 segments were each derived from the alternative parent. Loci critical for promoting hybrid vigor may be contained in each of these 12 conserved segments. We have identified genes with similar altered expression in hybrid mimics and F1 plants but not in the small phenotype line. These genes may be critical for the generation of hybrid vigor. Analysis of transcriptomes indicated that increased expression of the transcription factor PHYTOCHROME-INTERACTING FACTOR (PIF4) may contribute to hybrid vigor by targeting the auxin biosynthesis gene YUCCA8 and the auxin signaling gene IAA29. A number of auxin responsive genes promoting leaf growth were up-regulated in the F1 hybrids and hybrid mimics, suggesting that increased auxin biosynthesis and signaling contribute to the hybrid phenotype. The hybrid mimic seeds had earlier germination as did the seeds of the F1 hybrids, indicating cosegregation of the genes for rosette size and the germination trait. Early germination may be an indicator of vigorous hybrids.

Relative efficiency of rhizobacteria for auxin biosynthesis in rhizosphere and non-rhizosphere soils

Soil Research ◽  
2004 ◽  
Vol 42 (8) ◽  
pp. 921 ◽  
Author(s):  
Azeem Khalid ◽  
Shermeen Tahir ◽  
Muhammad Arshad ◽  
Zahir Ahmad Zahir
Keyword(s):  
High Performance ◽  
Indole Acetic Acid ◽  
Microbial Population ◽  
Rhizosphere Soil ◽  
Root Exudation ◽  
Auxin Biosynthesis ◽  
Rhizosphere Soils ◽  
Auxin Synthesis ◽  
Plant Crop

Biosynthesis of auxins in the rhizosphere of different crops may vary because of quantitative and qualitative variations in microbial population and root exudation. A laboratory study was conducted to assess in vitro auxin biosynthesis, and biosynthesis in rhizosphere and non-rhizosphere soils of different crops (maize, sorghum, mungbean, cotton). Soils were inoculated with selected rhizobacteria with and without the auxin precursor L-tryptophan (L-TRP). Auxins were detected by colourimetry as indole acetic acid equivalents and confirmed by high performance liquid chromatography. Results revealed that 83% of the 60 rhizobacteria were capable of producing auxins in the absence of L-TRP. Auxin biosynthesis by the 8 most efficient rhizobacteria ranged from 5.0 to 12.1 mg/L broth medium. A comparison of rhizosphere v. non-rhizosphere soils indicated a greater accumulation of auxins in the rhizosphere soils than non-rhizosphere soils. Overall, inoculation of rhizosphere soils with selected rhizobacteria resulted in greater production of auxin (up to 10.4 mg/kg soil) than in inoculated non-rhizosphere soils (up to 5.76 mg/kg). Moreover, efficiency of these rhizobacteria for auxin biosynthesis in both rhizosphere and non-rhizosphere soils differed with crop and bacterial strain. Some rhizobacterial strains exhibited superiority over the indigenous microflora for auxin biosynthesis in soil. Application of L-TRP promoted auxin biosynthesis in both rhizosphere and non-rhizosphere soils. These findings imply that inoculation with suitable strains and/or amendment with L-TRP could promote auxin synthesis in the rhizosphere soil of a given crop, which may have consequences for better plant/crop growth.

Transcription Factor Integration from Pathways Regulating Adult Blood Stem Cell Production and Self-Renewal.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. sci-14-sci-14
Author(s):  
Leonard I. Zon
Keyword(s):  
Stem Cell ◽  
Signaling Pathways ◽  
Binding Sites ◽  
Wnt Pathway ◽  
Dominant Negative ◽  
Transgenic Zebrafish ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Transcriptional Output ◽  
Multiple Signaling

Self-renewal of hematopoietic stem cells (HSCs) involves multiple signaling and transcription factors. We recently showed that prostaglandin (PG) E2 regulates the induction and engraftment of vertebrate HSC pathways. Yet, the targets and transcriptional output of the PGE2 pathway remains to be defined. The wnt pathway similarly affects HSC formation; activation of wnt signaling in heat-shock inducible transgenic zebrafish led to enhanced HSC formation, while inhibition of wnt/β-catenin signaling at the membrane level (dickkopf), in the cytosol (axin) or in the nucleus (dominant negative TCF), reduced HSC numbers. Using wnt transcriptional reporter zebrafish with multimerized TCF-binding sites. PGE2 was found to increase activity during embryonic development, demonstrating a direct interaction between these signaling pathways. The transcriptional output of the wnt pathway is linked to the interaction of TCF with β-catenin. Based on the transcriptional increase in multimerized TCF binding sites in vivo, we had hypothesized that prostaglandin signaling directly stimulates β-catenin activation. β-catenin is known to be phosphorylated on critical residues that modulate its activity. In marrow-derived cells, we demonstrate that prostaglandin increases a cyclic AMP pathway that leads to the PKA phosphorylation of β-catenin, thereby increasing its transcriptional activity. In HSCs, the interaction of multiple signaling pathways with transcriptional output is a method for modulating self-renewal in the stem cell pool as well as tissue differentiation.

scholarly journals The effect of NGATHA altered activity on auxin signaling pathways within the Arabidopsis gynoecium

2014 ◽  
Vol 5 ◽  
Author(s):  
Irene Martínez-Fernández ◽  
Sofía Sanchís ◽  
Naciele Marini ◽  
Vicente Balanzá ◽  
Patricia Ballester ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Auxin Signaling

scholarly journals Transcriptome Analysis Reveals Multiple Hormones, Wounding and Sugar Signaling Pathways Mediate Adventitious Root Formation in Apple Rootstock

2018 ◽  
Vol 19 (8) ◽  
pp. 2201 ◽  
Author(s):  
Ke Li ◽  
Yongqi Liang ◽  
Libo Xing ◽  
Jiangping Mao ◽  
Zhen Liu ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Signaling Pathway ◽  
Molecular Mechanisms ◽  
Expression Patterns ◽  
Signalling Pathways ◽  
Auxin Signaling ◽  
Strong Positive Correlation ◽  
Sugar Signaling ◽  
Apple Rootstocks ◽  
Auxin Signaling Pathway

Adventitious roots (AR) play an important role in the vegetative propagation of apple rootstocks. The potential role of hormone, wounding, and sugar signalling pathways in mediating AR formation has not been adequately explored and the whole co-expression network in AR formation has not been well established in apple. In order to identify the molecular mechanisms underlying AR formation in ‘T337’ apple rootstocks, transcriptomic changes that occur during four stages of AR formation (0, 3, 9 and 16 days) were analyzed using high-throughput sequencing. A total of 4294 differentially expressed genes were identified. Approximately 446 genes related to hormones, wounding, sugar signaling, root development, and cell cycle induction pathways were subsequently selected based on their potential to be involved in AR formation. RT-qPCR validation of 47 genes with known functions exhibited a strong positive correlation with the RNA-seq data. Interestingly, most of the candidate genes involved in AR formation that were identified by transcriptomic sequencing showed auxin-responsive expression patterns in an exogenous Indole-3-butyric acid (IBA)-treatment assay: Indicating that endogenous and exogenous auxin plays key roles in regulating AR formation via similar signalling pathways to some extent. In general, AR formation in apple rootstocks is a complex biological process which is mainly influenced by the auxin signaling pathway. In addition, multiple hormones-, wounding- and sugar-signaling pathways interact with the auxin signaling pathway and mediate AR formation in apple rootstocks.

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