scholarly journals A DAO1-Mediated Circuit Controls Auxin and Jasmonate Crosstalk Robustness during Adventitious Root Initiation in Arabidopsis

2019 ◽  
Vol 20 (18) ◽  
pp. 4428 ◽  
Author(s):  
Abdellah Lakehal ◽  
Asma Dob ◽  
Ondřej Novák ◽  
Catherine Bellini
Keyword(s):  
Adventitious Root ◽  
Adventitious Rooting ◽  
Negative Regulator ◽  
Early Event ◽  
Auxin Signaling ◽  
Loss Of Function ◽  
Genetic Components ◽  
Mechanistic Basis ◽  
Ja Signaling

Adventitious rooting is a post-embryonic developmental program governed by a multitude of endogenous and environmental cues. Auxin, along with other phytohormones, integrates and translates these cues into precise molecular signatures to provide a coherent developmental output. Auxin signaling guides every step of adventitious root (AR) development from the early event of cell reprogramming and identity transitions until emergence. We have previously shown that auxin signaling controls the early events of AR initiation (ARI) by modulating the homeostasis of the negative regulator jasmonate (JA). Although considerable knowledge has been acquired about the role of auxin and JA in ARI, the genetic components acting downstream of JA signaling and the mechanistic basis controlling the interaction between these two hormones are not well understood. Here we provide evidence that COI1-dependent JA signaling controls the expression of DAO1 and its closely related paralog DAO2. In addition, we show that the dao1-1 loss of function mutant produces more ARs than the wild type, probably due to its deficiency in accumulating JA and its bioactive metabolite JA-Ile. Together, our data indicate that DAO1 controls a sensitive feedback circuit that stabilizes the auxin and JA crosstalk during ARI.

scholarly journals The microRNA476a/RFL module regulates adventitious root formation through a mitochondria-dependent pathway in Populus

2019 ◽  
Author(s):  
Changzheng Xu ◽  
Yuanxun Tao ◽  
Xiaokang Fu ◽  
Li Guo ◽  
Haitao Xing ◽  
...  
Keyword(s):  
Adventitious Root ◽  
Developmental Plasticity ◽  
Adventitious Rooting ◽  
Adventitious Root Formation ◽  
Auxin Signaling ◽  
Stem Cuttings ◽  
Pentatricopeptide Repeat ◽  
Dynamic Regulation ◽  
Mitochondrial Regulation ◽  
Mitochondrial Homeostasis

AbstractAdventitious root (AR) formation at the base of stem cuttings determines the efficiency of clonal propagation for woody plants. Many endogenous and environmental factors influence AR formation. However, our knowledge about the regulation of AR development by mitochondrial metabolism in plants is very limited. Here we identified Populus-specific miR476a as a novel regulator of wound-induced adventitious rooting via orchestrating mitochondrial homeostasis in poplar. MiR476a exhibited inducible expression during AR formation and directly targets several Restorer of Fertility like (RFL) genes encoding mitochondrion-localized pentatricopeptide repeat proteins. Genetic modification of miR476-RFL expression revealed the miR476/RFL-mediated dynamic regulation of mitochondrial homeostasis on AR formation in transgenic poplar. Furthermore, mitochondrial perturbation via exogenous chemical inhibitor validated that the miR476a/RFL-directed AR formation depended on mitochondrial regulation though modulating the auxin pathway. Our results established a miRNA-directed mitochondrion-auxin signaling cascade required for AR development, providing novel insights into the understanding of mitochondrial regulation on plant developmental plasticity.

scholarly journals Rewiring of auxin signaling under persistent shade

2018 ◽  
Vol 115 (21) ◽  
pp. 5612-5617 ◽  
Author(s):  
Ornella Pucciariello ◽  
Martina Legris ◽  
Cecilia Costigliolo Rojas ◽  
María José Iglesias ◽  
Carlos Esteban Hernando ◽  
...  
Keyword(s):  
Physiological Role ◽  
System Level ◽  
Early Event ◽  
Auxin Signaling ◽  
Detailed Knowledge ◽  
Shade Avoidance ◽  
Growth Responses ◽  
Molecular Events ◽  
Elevated Expression

Light cues from neighboring vegetation rapidly initiate plant shade-avoidance responses. Despite our detailed knowledge of the early steps of this response, the molecular events under prolonged shade are largely unclear. Here we show that persistent neighbor cues reinforce growth responses in addition to promoting auxin-responsive gene expression in Arabidopsis and soybean. However, while the elevation of auxin levels is well established as an early event, in Arabidopsis, the response to prolonged shade occurs when auxin levels have declined to the prestimulation values. Remarkably, the sustained low activity of phytochrome B under prolonged shade led to (i) decreased levels of PHYTOCHROME INTERACTING FACTOR 4 (PIF4) in the cotyledons (the organs that supply auxin) along with increased levels in the vascular tissues of the stem, (ii) elevated expression of the PIF4 targets INDOLE-3-ACETIC ACID 19 (IAA19) and IAA29, which in turn reduced the expression of the growth-repressive IAA17 regulator, (iii) reduced abundance of AUXIN RESPONSE FACTOR 6, (iv) reduced expression of MIR393 and increased abundance of its targets, the auxin receptors, and (v) elevated auxin signaling as indicated by molecular markers. Mathematical and genetic analyses support the physiological role of this system-level rearrangement. We propose that prolonged shade rewires the connectivity between light and auxin signaling to sustain shade avoidance without enhanced auxin levels.

scholarly journals The histidine phosphotransfer AHP4 plays a negative role in Arabidopsis plant response to drought

2020 ◽  
Author(s):  
Chien Van Ha ◽  
Kien Huu Nguyen ◽  
Mohammad Golam Mostofa ◽  
Cuong Duy Tran ◽  
Yasuko Watanabe ◽  
...  
Keyword(s):  
Function Analysis ◽  
Negative Regulator ◽  
Large Set ◽  
Loss Of Function ◽  
Ros Scavenging ◽  
Biochemical Processes ◽  
Drought Tolerant ◽  
Physiological And Biochemical ◽  
Histidine Phosphotransfer

ABSTRACTCytokinin plays an important role in plant stress responses via a multistep signaling pathway, involving the histidine phosphotransfer proteins (HPs). In Arabidopsis thaliana, the AHP2, AHP3 and AHP5 proteins are known to impact drought responses; however, the role of AHP4 in drought adaptation remains undetermined. In the present study, using a loss-of-function approach we showed that AHP4 possesses a negative regulatory role in Arabidopsis’s response to drought. This is evidenced by both higher survival rates of ahp4 than wild-type (WT) plants under drought conditions, and the down-regulated AHP4 expression in WT during periods of dehydration. Comparative transcriptome analysis of ahp4 and WT plants revealed AHP4-mediated expression of several dehydration- and/or abscisic acid (ABA)-responsive genes involved in regulation of various physiological and biochemical processes important for plant drought acclimation. In comparison with WT, ahp4 plants showed increased wax crystal accumulation in stems, thicker cuticles in leaves, greater sensitivity to exogenous ABA at germination, narrow stomatal apertures, heightened leaf temperatures during dehydration, and longer root length under osmotic stress. Additionally, ahp4 plants showed greater photosynthetic efficiency, lower levels of reactive oxygen species (ROS), reduced electrolyte leakage and lipid peroxidation, and increased anthocyanin contents under drought, when compared with WT. These differences displayed in ahp4 plants are likely due to up-regulation of genes that encode enzymes involved in ROS-scavenging and non-enzymatic antioxidant metabolism. The role of AHP4 in negative regulation of multiple protective mechanisms associated with drought tolerance could make editing of AHP4 a promising approach for the production of drought-tolerant crop plants.Significance statementLoss-of-function analysis of the cytokinin signaling member AHP4 revealed its function in Arabidopsis adaptation to drought as a negative regulator, affecting various physiological and biochemical processes by modulating the expression of a large set of genes potentially in a crosstalk with ABA. AHP4 and its homologs are promising candidates for gene editing to develop drought-tolerant crop cultivars.

scholarly journals An auxin signaling network translates low-sugar-state input into compensated cell enlargement in the fugu5 cotyledon

PLoS Genetics ◽  
2021 ◽  
Vol 17 (8) ◽  
pp. e1009674
Author(s):  
Hiromitsu Tabeta ◽  
Shunsuke Watanabe ◽  
Keita Fukuda ◽  
Shizuka Gunji ◽  
Mariko Asaoka ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Molecular Mechanisms ◽  
Genetic Interaction ◽  
Mitotic Cell ◽  
Fine Tuning ◽  
Auxin Signaling ◽  
Cell Enlargement ◽  
Loss Of Function ◽  
Nutrient Reserves

In plants, the effective mobilization of seed nutrient reserves is crucial during germination and for seedling establishment. The Arabidopsis H+-PPase-loss-of-function fugu5 mutants exhibit a reduced number of cells in the cotyledons. This leads to enhanced post-mitotic cell expansion, also known as compensated cell enlargement (CCE). While decreased cell numbers have been ascribed to reduced gluconeogenesis from triacylglycerol, the molecular mechanisms underlying CCE remain ill-known. Given the role of indole 3-butyric acid (IBA) in cotyledon development, and because CCE in fugu5 is specifically and completely cancelled by ech2, which shows defective IBA-to-indoleacetic acid (IAA) conversion, IBA has emerged as a potential regulator of CCE. Here, to further illuminate the regulatory role of IBA in CCE, we used a series of high-order mutants that harbored a specific defect in IBA-to-IAA conversion, IBA efflux, IAA signaling, or vacuolar type H+-ATPase (V-ATPase) activity and analyzed the genetic interaction with fugu5–1. We found that while CCE in fugu5 was promoted by IBA, defects in IBA-to-IAA conversion, IAA response, or the V-ATPase activity alone cancelled CCE. Consistently, endogenous IAA in fugu5 reached a level 2.2-fold higher than the WT in 1-week-old seedlings. Finally, the above findings were validated in icl–2, mls–2, pck1–2 and ibr10 mutants, in which CCE was triggered by low sugar contents. This provides a scenario in which following seed germination, the low-sugar-state triggers IAA synthesis, leading to CCE through the activation of the V-ATPase. These findings illustrate how fine-tuning cell and organ size regulation depend on interplays between metabolism and IAA levels in plants.

A phase II study of everolimus in patients with aggressive RAI refractory (RAIR) thyroid cancer (TC).

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 6023-6023 ◽  
Author(s):  
Jochen H. Lorch ◽  
Naifa Busaidy ◽  
Daniel T Ruan ◽  
Pasi A. Janne ◽  
Sewanti Atul Limaye ◽  
...  
Keyword(s):  
Phase Ii ◽  
Phase Ii Study ◽  
Protein A ◽  
Progression Free Survival ◽  
Complete Response ◽  
Negative Regulator ◽  
High Rate ◽  
Loss Of Function ◽  
Open Label ◽  
Mechanistic Basis

6023 Background: We present results of an open label phase II study of the mTOR inhibitor Everolimus in patients (pts) with RAIR TC. Methods: Pts with metastatic, incurable RAIR TC who had shown radiographic progression within 6 months prior to enrollment received Everolimus 10mg orally once daily. Responses were monitored by CT's every two months. The primary endpoint was progression free survival. Sequential biopsies were obtained in selected pts. Results: Enrollment to the differentiated TC (DTC) cohort finished in Jan 2013 and included 33 pts, among them 11 with Hurthle cell TC. Exploratory cohorts enrolled 10 pts with medullary [MTC] and 5 with anaplastic [ATC] with 2 added openings remaining for ATC. For the DTC cohort, median time on study to date is 10 months (mo) (<1-23+). 31 pts are evaluable at this time. PFS in the DTC cohort by Kaplan-Meier (K-M) analysis is 16.0 mo (95%CI 10-NR). Currently, disease stability for 6 and 12 mo or more was achieved in 18 and 10/31 pts, respectively, 11 pts remain on study. Median OS was not reached but 1 year survival by K-M analysis was 76%. One pt achieved a PR. 3 pts with DTC underwent sequential biopsies which revealed activation of autophagy while markers for apoptosis were not detected. Among 10 MTC pts, one achieved a PR and 9 pts had stable disease for 6 mo or more (6-33+). Among 5 ATC pts, 3 progressed, one has ongoing disease stability for 5 mo. One patient achieved a complete response that lasted for 18 mo and whole exome sequencing revealed somatic loss of function mutation affecting the Tuberous Sclerosis 2 (TSC2) protein, a negative regulator of mTOR activity [TSC2 (Q1178*) and FLCN (R17fs)]. Most common treatment-related adverse events were as anticipated and included fatigue, stomatitis and infections. Grade (gr) 3 events included infection 5, weight loss 3, leukopenia 3, thrombocytopenia 3, fatigue 3, hypophosphatemia 2, stomatitis 2, pneumonitis 1 and thrombosis 1pts. One pt had gr 4 hypercholesterinemia and one pt had gr 4 leukopenia. Conclusions: Everolimus has significant anti-tumor activity in pts with advanced TC. Activation of autophagy could account for high rate of disease stability. Sequencing may identify mechanistic basis and predictive markers for treatment response. Clinical trial information: NCT00936858.

scholarly journals ETHYLENE RESPONSE FACTOR 115 integrates jasmonate and cytokinin signaling machineries to repress adventitious rooting in Arabidopsis

2019 ◽  
Author(s):  
Abdellah Lakehal ◽  
Asma Dob ◽  
Zahra Rahneshan ◽  
Ondřej Novák ◽  
Sacha Escamez ◽  
...  
Keyword(s):  
Plant Immunity ◽  
Adventitious Rooting ◽  
Molecular Network ◽  
Ethylene Response Factor ◽  
Response Factor ◽  
Cytokinin Signaling ◽  
Ethylene Response ◽  
Mechanistic Basis ◽  
Ja Signaling ◽  
Precise Role

ABSTRACTJasmonate (JA), an oxylipin-derived phytohormone, plays crucial roles not only in plant immunity and defense against herbivorous insects but also in plant growth and developmental processes, including regeneration and organogenesis. However, the mechanistic basis of its mode of action and precise role in integrating other signaling cues are poorly understood. Here we provide genetic evidences that JA signaling acts in both NINJA-dependent and -independent modulation of the transcriptional activity of MYC transcription factors involved in the inhibition of adventitious root initiation (ARI). Our data show that NINJA-dependent JA signaling in pericycle cells blocks early events of ARI. Moreover, transcriptomic comparison of ninja-1myc2-322B double mutant (which produce extremely few ARs) and wild type seedlings identified a novel molecular network governed by the APETALA2/ETHYLENE RESPONSE FACTOR 115 (ERF115) transcription factor. We demonstrate that JA-induced ERF115 activates the cytokinin signaling machinery and thereby represses ARI. Altogether, our results reveal a molecular network involving cooperative crosstalk between JA and CK machineries that inhibits ARI.

scholarly journals An analysis of the regulation of DNA synthesis by cdk2, Cip1, and licensing factor.

1995 ◽  
Vol 129 (1) ◽  
pp. 1-15 ◽  
Author(s):  
H Yan ◽  
J Newport
Keyword(s):  
Dna Replication ◽  
Kinase Inhibitor ◽  
Negative Regulator ◽  
Sperm Chromatin ◽  
Early Event ◽  
Replication Process ◽  
P21 Protein ◽  
Licensing Factor ◽  
Additional Support

The activation of DNA replication appears to involve at least four steps. These include origin recognition, origin unwinding, primer synthesis, and a switching step to a continuous elongation mode. Moreover, in higher eukaryotes a number of studies have shown that much of the DNA replication which occurs is restricted to specific sites within the nuclei. It has been proposed that these replication foci are composed of a large number of origin sites which are clustered together into an aggregate. The molecular basis for this aggregation is currently not well understood. Regulation of the activation of DNA replication is a complicated process. The G1-S kinase cdk2 is a positive regulator of replication. The p21 protein is a negative regulator of replication both by inhibiting cdk2 kinase and the replication protein PCNA. Moreover, it has been proposed that origin usage is restricted to a single firing per cell cycle by a "licensing factor." Using a cell-free replication system derived from Xenopus eggs we have investigated at what step in the replication process these regulators participate. We present evidence that the clustered organization of DNA into foci is not a transient arrangement, but rather, it persists following DNA replication. We also find that foci form on both sperm chromatin and bacteriophage lambda DNA incubated in extracts depleted of cdk2 kinase. Therefore, our data support the conclusion that organization of chromatin into foci is an early event in the replication pathway preceding activation of cdk2 kinase. With respect to the role of cdk2 during activation of DNA replication we find that in cdk2-depleted extracts primer synthesis does not occur and RP-A remains tightly associated with foci. This strongly suggests that cdk2 kinase is required for activating the origin unwinding step of the replication process. Consistent with this interpretation we find that addition of rate limiting quantities of the cdk2 inhibitor p21 protein to an extract delays primer synthesis. Interestingly, in the presence of p21 primer synthesis does occur after a delay and then replication arrests. This is consistent with the published demonstration that p21 can inhibit PCNA, a protein required for replication beyond the priming step. Therefore, our results provide additional support to the proposal that the post-priming switching step is a key regulatory step in replication. With respect to the role of licensing factor during DNA replication it has recently been shown that treatment of mitotic extracts with kinase inhibitor DMAP inactivates "licensing factor."(ABSTRACT TRUNCATED AT 400 WORDS)

AUXIN BINDING PROTEIN 4 is involved in the Ca2+/auxin-regulated expression of ZCAX3 gene in maize (Zea mays)

Botany ◽  
2014 ◽  
Vol 92 (5) ◽  
pp. 332-339
Author(s):  
Dejana Jurišić-Knežev ◽  
Véronique Bergougnoux ◽  
David Milde ◽  
Martin Fellner
Keyword(s):  
Zea Mays ◽  
Inhibitory Effect ◽  
Auxin Signaling ◽  
Loss Of Function ◽  
Significant Drop ◽  
Exogenous Auxin ◽  
Regulated Expression ◽  
Auxin Binding ◽  
Auxin Binding Proteins

As a second messenger, calcium is involved in auxin signaling, and previous studies demonstrated that Arabidopsis CAX1 (Ca2+/H+ exchanger) is involved in the auxin transduction pathway. This study was performed to investigate the possible role of auxin-binding proteins ABP1 and ABP4 in Ca2+/auxin-regulated growth in maize (Zea mays L.). We identified and cloned two AtCAX1 homologs in maize, ZCAX2 and ZCAX3. Using maize loss-of-function abp1 and abp4 mutants, the role of ABPs in Ca2+-dependent growth and in the Ca2+/auxin-regulated expression of the CAX genes was investigated in etiolated maize seedlings. Exogenous Ca2+ enhanced mesocotyl but not coleoptile growth in WT, abp1, abp4, and abp1/abp4 mutants, but the maximum stimulation was in abp4. As well, in the abp4 mutant, maximum accumulation of Ca2+ was observed when seedlings were exposed to exogenous Ca2+. In the mesocotyl of abp4 and double mutants, the expression of ZCAX3 was significantly reduced in the absence of exogenous Ca2+, whereas exogenous Ca2+ significantly up-regulated its expression in both mutants. This effect of Ca2+ was not observed in the coleoptile. In the absence of NAA, knockout of ABP4 led to significant drop of ZCAX3 expression in the mesocotyl, and exogenous auxin significantly inhibited expression of the ZCAX3 in WT, but not in abp mutants. This effect of auxin was not observed in the coleoptile. Our results indicate that in the absence of NAA, functional ABP4 is required for ZCAX3 expression and that ABP4 mediates the inhibitory effect of NAA on ZCAX3 expression. We provided evidence for a cross talk between ABP4, exogenous auxin, Ca2+, and ZCAX3 during growth of etiolated maize mesocotyl.

scholarly journals Molecular basis of differential adventitious rooting competence in poplar genotypes

2021 ◽  
Author(s):  
Alok Ranjan ◽  
Irene Perrone ◽  
Sanaria Alallaq ◽  
Rajesh Singh ◽  
Adeline Rigal ◽  
...  
Keyword(s):  
Molecular Basis ◽  
Hybrid Poplar ◽  
Adventitious Rooting ◽  
Negative Regulator ◽  
Differentially Expressed ◽  
Genotypic Differences ◽  
Ros Scavenging ◽  
Genes Encoding ◽  
Commercially Important

Recalcitrance to adventitious root (AR) development is a major hurdle for propagation of commercially important woody plants. Although significant progress has been made to identify genes involved in subsequent steps of AR development, the molecular basis of recalcitrance to form AR between easy-to-root compaired to difficult-to-root genotypes remain unknown. To address this, we generated cambium tissue specific transcriptomic data from stem cutting of hybrid aspen, T89 (difficult-to-root) and hybrid poplar OP42 (easy-to-root) and used transgenic approaches to verify the role of several transcription factors (TF) in the control of adventitious rooting. Increased peroxidase activity is often positively correlated with better rooting and in agreement, an enrichment of differentially expressed genes encoding Reactive Oxygen Species (ROS) scavenging proteins was observed in OP42 compared to T89. OP42 cambium cells displayed a more intense transcriptional reprograming as highlighted by the higher number of differentially expressed TF compared to T89. PtMYC2, a potential negative regulator, was less expressed in OP42 compared to T89. Using transgenic approaches, we demonstrated that PttARF17.1 and PttMYC2.1 negatively regulate adventitious rooting. These results thus provide insight into molecular basis of genotypic differences in AR and implicate differential expression of master regulator MYC2 as a critical player in this process.

scholarly journals Genome-wide fitness assessment during diurnal growth reveals an expanded role of the cyanobacterial circadian clock protein KaiA

2018 ◽  
Author(s):  
David G. Welkie ◽  
Benjamin E. Rubin ◽  
Yong-Gang Chang ◽  
Spencer Diamond ◽  
Scott A. Rifkin ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Environmental Changes ◽  
Time Of Day ◽  
Negative Regulator ◽  
Starvation Period ◽  
Night Time ◽  
Photosynthetic Organisms ◽  
Genetic Components ◽  
Clock Protein

AbstractThe recurrent pattern of light and darkness generated by Earth’s axial rotation has profoundly influenced the evolution of organisms, selecting for both biological mechanisms that respond acutely to environmental changes and circadian clocks that program physiology in anticipation of daily variations. The necessity to integrate environmental responsiveness and circadian programming is exemplified in photosynthetic organisms such as cyanobacteria, which depend on light-driven photochemical processes. The cyanobacterium Synechococcus elongatus PCC 7942 is an excellent model system for dissecting these entwined mechanisms. Its core circadian oscillator, consisting of three proteins KaiA, KaiB, and KaiC, transmits time-of-day signals to clock-output proteins, which reciprocally regulate global transcription. Research performed under constant light facilitates analysis of intrinsic cycles separately from direct environmental responses, but does not provide insight into how these regulatory systems are integrated during light-dark cycles. Thus, we sought to identify genes that are specifically necessary in a day-night environment. We screened a dense bar-coded transposon library in both continuous light and daily cycling conditions and compared the fitness consequences of loss of each nonessential gene in the genome. Although the clock itself is not essential for viability in light-dark cycles, the most detrimental mutations revealed by the screen were those that disrupt KaiA. The screen broadened our understanding of light-dark survival in photosynthetic organisms, identified unforeseen clock-protein interaction dynamics, and reinforced the role of the clock as a negative regulator of a night-time metabolic program that is essential for S. elongatus to survive in the dark.SignificanceUnderstanding how photosynthetic bacteria respond to and anticipate natural light–dark cycles is necessary for predictive modeling, bioengineering, and elucidating metabolic strategies for diurnal growth. Here, we identify the genetic components that are important specifically under light-dark cycling conditions and determine how a properly functioning circadian clock prepares metabolism for darkness, a starvation period for photoautotrophs. This study establishes that the core circadian clock protein KaiA is necessary to enable rhythmic de-repression of a night-time circadian program.

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