IBR5

Biodiversity in plant shape is mainly attributable to the diversity of leaf shape, which is largely determined by the transient morphogenetic activity of the leaf margin that creates leaf serrations. However, the precise mechanism underlying the establishment of this morphogenetic capacity remains poorly understood. We report here that INDOLE-3-BUTYRIC ACID RESPONSE 5 (IBR5), a dual-specificity phosphatase, is a key component of leaf-serration regulatory machinery. Loss-of-function mutants of IBR5 exhibited pronounced serrations due to increased cell area...

Histone H2B monoubiquitination (H2Bub1) is recognized as a regulatory mechanism that controls a range of cellular processes. We previously showed that H2Bub1 was involved in responses to biotic stress in Arabidopsis. However, the molecular regulatory mechanisms of H2Bub1 in controlling responses to abiotic stress remain limited. Here, we report that HISTONE MONOUBIQUITINATION1 (HUB1) and HUB2 played important regulatory roles in response to salt stress. Phenotypic analysis revealed that H2Bub1 mutants confer decreased tolerance to salt stress...

ABP1 and TIR1/AFBs are known as auxin receptors. ABP1 is linked to auxin responses several of which are faster than 10 min. TIR1 regulates auxin-induced transcription of early auxin genes also within minutes. We use transcription of such TIR1-dependent genes as indicator of TIR1 activity to show the rapid regulation of TIR1 by exogenous auxin. To this end, we used quantification of transcription of a set of fifteen early auxin-induced reporter genes at t = 10 and t = 30 min to measure this as a TIR1-dependent auxin response...

As a prominent regulator of plant growth and development, the hormone auxin plays an essential role in controlling cell division and expansion. Auxin-responsive gene transcription is mediated through the TRANSPORT INHIBITOR RESPONSE1/AUXIN SIGNALING F-BOX (TIR1/AFB) pathway. Roles for TIR1/AFB pathway components in auxin response are understood best, but additional factors implicated in auxin responses require more study. The function of these factors, including S-Phase Kinase-Associated Protein 2A (SKP2A), SMALL AUXIN UP RNAs (SAURs), INDOLE 3-BUTYRIC ACID RESPONSE5 (IBR5), and AUXIN BINDING PROTEIN1 (ABP1), has remained largely obscure...

[This corrects the article DOI: 10.1371/journal.pgen.1005584.].

Plant responses to low temperature are tightly associated with defense responses. We previously characterized the chilling-sensitive mutant chs3-1 resulting from the activation of the Toll and interleukin 1 receptor-nucleotide binding-leucine-rich repeat (TIR-NB-LRR)-type resistance (R) protein harboring a C-terminal LIM (Lin-11, Isl-1 and Mec-3 domains) domain. Here we report the identification of a suppressor of chs3, ibr5-7 (indole-3-butyric acid response 5), which largely suppresses chilling-activated defense responses...

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Mitogen-activated dual-specificity MAPK phosphatases are important negative regulators in the MAPK signalling pathways responsible for many essential processes in plants. In a screen for mutants with reduced organ size we have identified a mutation in the active site of the dual-specificity MAPK phosphatase indole-3-butyric acid-response5 (IBR5) that we named tinkerbell (tink) due to its small size. Analysis of the tink mutant indicates that IBR5 acts as a novel regulator of organ size that changes the rate of growth in petals and leaves...

The INDOLE-3-BUTYRIC ACID RESPONSE5 (IBR5) gene encodes a dual specificity phosphatase that regulates plant auxin responses. IBR5 has been predicted to generate two transcripts through alternative splicing, but alternative splicing of IBR5 has not been confirmed experimentally. The previously characterized ibr5-1 null mutant exhibits many auxin related defects such as auxin insensitive primary root growth, defective vascular development, short stature and reduced lateral root development. However, whether all these defects are caused by the lack of phosphatase activity is not clear...

The mitogen-activated protein kinase (MAPK) phosphatases (MKPs) are important negative regulators in the MAPK signaling pathways, which play crucial roles in plant growth, regulation of development and response to environment stresses. Several MAPKs have been reported to be involved in the drought stress response, however, there is no evidence for the specific function of MKPs in drought stress. Here, a putative MKP in rice (Oryza sativa), OsIBR5, was characterized. Expression of OsIBR5 was induced by PEG6000, abscisic acid (ABA) and hydrogen peroxide (H(2)O(2))...

Root morphogenesis is controlled by the regulation of cell division and expansion. We isolated an allele of the eto1 ethylene overproducer as a suppressor of the auxin-resistant mutant ibr5, prompting an examination of crosstalk between the phytohormones auxin and ethylene in control of root epidermal cell elongation and root hair elongation. We examined the interaction of eto1 with mutants that have reduced auxin response or transport and found that ethylene overproduction partially restored auxin responsiveness to these mutants...

Mitogen-activated protein kinase (MAPK) phosphatases are important negative regulators in the MAPK signaling pathways responsible for many essential processes in plants, including development, stress management and hormonal responses. A mutation in INDOLE-3-BUTYRIC ACID-RESPONSE5 (IBR5), which is predicted to encode a dual-specificity MAPK phosphatase, was previously reported to confer reduced sensitivity to auxin and ABA in Arabidopsis roots. To further characterize IBR5, and to understand how it might help integrate MAPK cascades with hormone signaling, we searched for IBR5-interacting MAPKs...

Auxin controls numerous plant growth processes by directing cell division and expansion. Auxin-response mutants, including iba response5 (ibr5), exhibit a long root and decreased lateral root production in response to exogenous auxins. ibr5 also displays resistance to the phytohormone abscisic acid (ABA). We found that the sar3 suppressor of auxin resistant1 (axr1) mutant does not suppress ibr5 auxin-response defects, suggesting that screening for ibr5 suppressors might reveal new components important for phytohormone responsiveness...

BACKGROUND: In Arabidopsis, INDOLE-3-BUTYRIC ACID RESPONSE5 (IBR5), a putative dual-specificity protein phosphatase, is a positive regulator of auxin response. Mutations in IBR5 result in decreased plant height, defective vascular development, increased leaf serration, fewer lateral roots, and resistance to the phytohormones auxin and abscisic acid. However, the pathways through which IBR5 influences auxin responses are not fully understood. RESULTS: We analyzed double mutants of ibr5 with other mutants that dampen auxin responses and found that combining ibr5 with an auxin receptor mutant, tir1, enhanced auxin resistance relative to either parent...

The lowest energy transition state for the nondissociative apical/equatorial atom exchange mechanism for three square pyramidal AEX5 molecular species was calculated (CCSD(T)/pVTZ; B3LYP/pVTZ, aug-cc-pV5Z) to have a hemidirected geometry with C(s) symmetry for BrF5, IF5, and XeF5+. In contrast, holodirected C2v-symmetric transition states for this process were located for the AEX5 square pyramidal molecules ClF5, ICl5, and IBr5. Imaginary frequencies were calculated and examined in a visual/dynamic fashion to gain insight into these fluxional processes...

Auxin is an important plant hormone that plays significant roles in plant growth and development. Although numerous auxin-response mutants have been identified, auxin signal transduction pathways remain to be fully elucidated. We isolated ibr5 as an Arabidopsis indole-3-butyric acid-response mutant, but it also is less responsive to indole-3-acetic acid, synthetic auxins, auxin transport inhibitors, and the phytohormone abscisic acid. Like certain other auxin-response mutants, ibr5 has a long root and a short hypocotyl when grown in the light...

The effects of coronary blood flow, tissue water content and hematocrit variation on the Integrated Myocardial Backscatter Rayleigh 5 (IBR5) and Fourier coefficient of amplitude modulation (FAM, an index of cardiac cycle-dependent variation in IBR5) were measured in five open chest dogs. Data were obtained at baseline, during adenosine infusion and after two hours of crystalloid hemodilution (Hct 15%). IBR5 of -46.4 +/- .94 dB at baseline did not change significantly during adenosine infusion (-45 +/- .85 dB) and after hemodilution (-46...

BACKGROUND: Ultrasonic backscatter demonstrates a cardiac cycle-dependent modulation. The exact mechanism of the modulation is under debate. The objective of the present study was to test the hypothesis that a change in size and configuration of myofilaments from systole to diastole alters acoustic propagation properties and backscatter. METHODS AND RESULTS: In vivo measurements were made of integrated backscatter at 5 MHz (IBR5), followed by in vitro measurements of ultrasonic attenuation, speed, and heterogeneity index using a scanning laser acoustic microscope at 100 MHz...

BACKGROUND: Identification of viable but stunned myocardium remains a major problem. Since stunned myocardium results in impairment of myocardial function without any structural damage and infarcted myocardium causes major structural disruption, we postulated that acoustic properties could distinguish between the two insults. METHODS AND RESULTS: Anesthetized open-chest dogs underwent a total occlusion of the left anterior descending coronary artery for 15 minutes (stunned, n = 7) and 90 minutes (infarcted, n = 8), followed by reperfusion for 3 hours...

Ultrasonic backscatter is substantially modified by pathologic changes in myocardium. Influence of physiologic changes in heart rate, mean arterial pressure, preload, and inotropic state were studied in 17 anesthetized open-chest dogs. Heart rate was changed with atrial pacing/ULFS'49 (a selective bradycardiac agent). Mean arterial pressure was varied with aortic constriction/nitroprusside, preload was altered with nitroglycerin/volume infusion, and inotropic states were altered with dobutamine (10 microns/kg)/esmolol (100 microns/kg)...