1,721,153 research outputs found
VIP1 is very important/interesting protein 1 regulating touch responses of Arabidopsis
No full textVIP1 (VIRE2-INTERACTING PROTEIN 1) is a bZIP transcription factor in Arabidopsis thaliana. VIP1 and its close homologs (i.e., Arabidopsis group I bZIP proteins) are present in the cytoplasm under steady conditions, but are transiently localized to the nucleus when cells are exposed to hypo-osmotic conditions, which mimic mechanical stimuli such as touch. Recently we have reported that overexpression of a repression domain-fused form of VIP1 represses the expression of some touch-responsive genes, changes structures and/or local auxin responses of the root cap cells, and enhances the touch-induced root waving. This raises the possibility that VIP1 suppresses touch-induced responses. VIP1 should be useful to further characterize touch responses of plants. Here we discuss 2 seemingly interesting perspectives about VIP1: (1) What factors are involved in regulating the nuclear localization of VIP1?; (2) What can be done to further characterize the physiological functions of VIP1 and other Arabidopsis group I bZIP proteins
Possible inhibition of Arabidopsis VIP1-mediated mechanosensory signaling by streptomycin
No full textVIP1 (VIRE2-INTERACTING PROTEIN 1) and its close homologues are Arabidopsis thaliana bZIP proteins regulating stress responses and root tropisms. They are present in the cytoplasm under steady conditions, but transiently accumulate in the nucleus when cells are exposed to mechanical stress such as hypo-osmotic stress and touch. This pattern of changes in subcellular localization is unique to VIP1 and its close homologues, and can be useful to further characterize mechanical stress signaling in plants. A recent study showed that calcium signaling regulates this pattern of subcellular localization. Here, we show that a possible calcium channel inhibitor, streptomycin, also inhibits the nuclear accumulation of VIP1. Candidates for the specific regulators of the mechanosensitive calcium signaling are further discussed
Generation and characterization of constitutively nuclear-localized variants of VIP1.
No full text<p>(A) Schematic representations of the VIP1 variants. Numbers indicate amino acid positions of full-length VIP1. Lowercase letters (a–f) correspond to those in the panels B–D. NLS: nuclear localization signal; NES: nuclear export signal. (B) Subcellular localization of the VIP1 variants in onion cells. The indicated forms of VIP1 (a–f) were expressed as GFP-fused proteins in onion epidermal cells. For each construct, more than 10 cells were observed, and a representative image is shown. Scale bars = 100 µm. (C) Subcellular localization of the VIP1 variants in Arabidopsis. Roots of the transgenic Arabidopsis plants expressing GFP-fused VIP1 variants (forms a, d, e and f) were observed without being treated by a hypotonic solution. For each genotype, more than 10 plants were used for observation, and a representative image is shown. Scale bars = 100 µm. (D) Expression of the VIP1 variants retards the cotyledon growth under a mannitol-stressed condition. The transgenic plants expressing the GFP-fused VIP1 variants (35S-VIP1ΔN80-GFP, for example) were grown in the presence of 0 (Control) or 200 mM mannitol for 10 days, and their cotyledon lengths were measured. <i>vip1</i>, which lacks the 3′ region of the <i>VIP1</i> transcript because of a T-DNA insertion in the genomic region of <i>VIP1 </i><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0103930#pone.0103930-Li1" target="_blank">[13]</a>, is shown as control. Values are means ± SD. (n = 15–20). *: <i>P</i><0.05; **: <i>P</i><0.01 vs. the wild type in Student's <i>t</i>-test. (E) Quantitative RT-PCR analyses of expression of the genes with promoters containing AGCTGT/G in the transgenic plants expressing the VIP1 variants. The transgenic plants were grown in the presence of 0 (Control) or 200 mM mannitol (+ Mannitol) for 18 days, and sampled for RNA extraction and cDNA synthesis. Relative expression levels were calculated by the comparative cycle threshold (C<sub>T</sub>) method using <i>UBQ5</i> as an internal control gene. Data are means of three biological replicates. Error bars indicate SD.</p
Inositol Pyrophosphates Get the Vip1 Treatment
No full textInositol pyrophosphates are unique signaling molecules implicated in the regulation of diverse cellular processes. Two new studies by Mulugu et al. (2007) and Lee et al. (2007) extend the biological and metabolic diversity of this class of molecules. They identify yeast Vip1 as a new inositol pyrophosphate synthase and show that the products of Vip1 activity regulate a cyclin/cyclin-dependent kinase complex
Development of high affinity selective VIP1 receptor agonists
No full textThe biological effects of VIP are mediated by at least two VIP receptors: the VIP1 and the VIP2 receptors that were cloned in rat, human and mice. As the mRNA coding for each receptor are located in different tissues, it is likely that each receptor modulates different functions. It is therefore of interest to obtain selective agonists for each receptor subtype. In the present work, we achieved the synthesis of two VIP1 receptor selective agonists derived from secretin and GRF. [R16]chicken secretin had IC50 values of binding of 1, 10,000, 20, and 3000 nM for the rat VIP1-, VIP2-, secretin- and PACAP receptors, respectively. This peptide, however, had a weaker affinity for the human VIP1 receptor (IC50 of 60 nM). The chimeric, substituted peptide [K15,R16,L27]VIP(I-7)/GRF(8-27) had IC50 values of binding of 1, 10,000, 10,000 and 30,000 nM for the rat VIP1-, VIP2-, secretin- and PACAP receptors, respectively. Furthermore, its also showed an IC50 of 0.8 nM for the human VIP1 receptor and a low affinity for the human VIP2 receptor. It is unlikely that this GRF analogue interacted with a high affinity to the pituitary GRF receptors as it did not stimulate rat pituitary adenylate cyclase activity. The two described analogues stimulated maximally the adenylate cyclase activity on membranes expressing each receptor subtype.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
VIP1 response elements mediate mitogen-activated protein kinase 3-induced stress gene expression
No full textThe plant pathogen Agrobacterium tumefaciens transforms plant cells by delivering its T-DNA into the plant cell nucleus where it integrates into the plant genome and causes tumor formation. A key role of VirE2-interacting protein 1 (VIP1) in the nuclear import of T-DNA during Agrobacterium-mediated plant transformation has been unravelled and VIP1 was shown to undergo nuclear localization upon phosphorylation by the mitogen-activated protein kinase MPK3. Here, we provide evidence that VIP1 encodes a functional bZIP transcription factor that stimulates stress-dependent gene expression by binding to VIP1 response elements (VREs), a DNA hexamer motif. VREs are overrepresented in promoters responding to activation of the MPK3 pathway such as Trxh8 and MYB44. Accordingly, plants overexpressing VIP1 accumulate high levels of Trxh8 and MYB44 transcripts, whereas stress-induced expression of these genes is impaired in mpk3 mutants. Trxh8 and MYB44 promoters are activated by VIP1 in a VRE-dependent manner. VIP1 strongly enhances expression from a synthetic promoter harboring multiple VRE copies and directly interacts with VREs in vitro and in vivo. Chromatin immunoprecipitation assays of the MYB44 promoter confirm that VIP1 binding to VREs is enhanced under conditions of MPK3 pathway stimulation. These results provide molecular insight into the cellular mechanism of target gene regulation by the MPK3 pathway
In vitro properties of a high affinity selective antagonist of the VIP1 receptor
No full textA selective high affinity VIP1 receptor antagonist [Acetyl-His1, D- Phe2, Lys15, Arg16, Leu17] VIP(3-7)/GRF(8-27) or PG 97-269 was synthesized, by analogy with recently obtained selective VIP1 receptor agonists. The properties of the new peptide were evaluated on Chinese hamster ovary (CHO) cell membranes expressing either the rat VIP1-, rat VIP2- or the human VIP2- recombinant receptors and on LoVo cell membranes expressing exclusively the human VIP1 receptor. The IC50 values of 125I-VIP binding inhibition by PG 97-269 were 10, 2000, 2 and 3000 nM on the rat VIP1-, rat VIP2-, human VIP1- and human VIP2 receptors, respectively. PG 97-269 had a negligible affinity for the PACAP I receptor type. It did not stimulate adenylate cyclase activity, but inhibited competitively effect of VIP on the VIP1 receptor mediated stimulation of adenylate cyclase activity. The K(i) values were respectively of 15 ± 5 nM and 2 ± 1 nM for the rat and human VIP1 receptors. Thus the described molecule in the first reported VIP antagonist with an affinity in the nM range and with a high selectivity for the VIP1 receptor subclass. It may be useful for evaluation of the physiological role of VIP in rat and human tissues.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
VIP1 and Its Homologs Are Not Required for Agrobacterium-Mediated Transformation, but Play a Role in Botrytis and Salt Stress Responses
No full textThe bZIP transcription factor VIP1 interacts with the Agrobacterium virulence protein VirE2, but the role of VIP1 in Agrobacterium-mediated transformation remains controversial. Previously tested vip1-1 mutant plants produce a truncated protein containing the crucial bZIP DNA-binding domain. We generated the CRISPR/Cas mutant vip1-2 that lacks this domain. The transformation susceptibility of vip1-2 and wild-type plants is similar. Because of potential functional redundancy among VIP1 homologs, we tested transgenic lines expressing VIP1 fused to a SRDX repression domain. All VIP1-SRDX transgenic lines showed wild-type levels of transformation, indicating that neither VIP1 nor its homologs are required for Agrobacterium-mediated transformation. Because VIP1 is involved in innate immune response signaling, we tested the susceptibility of vip1 mutant and VIP1-SRDX plants to Pseudomonas syringae and Botrytis cinerea. vip1 mutant and VIP1-SRDX plants show increased susceptibility to B. cinerea but not to P. syringae infection, suggesting a role for VIP1 in B. cinerea, but not in P. syringae, defense signaling. B. cinerea susceptibility is dependent on abscisic acid (ABA) which is also important for abiotic stress responses. The germination of vip1 mutant and VIP1-SRDX seeds is sensitive to exogenous ABA, suggesting a role for VIP1 in response to ABA. vip1 mutant and VIP1-SRDX plants show increased tolerance to growth in salt, indicating a role for VIP1 in response to salt stress
Analysis of functions of VIP1 and its close homologs in osmosensory responses of Arabidopsis thaliana.
No full textVIP1 is a bZIP protein in Arabidopsis thaliana. VIP1 accumulates in the nucleus under hypo-osmotic conditions and interacts with the promoters of hypo-osmolarity-responsive genes, CYP707A1 and CYP707A3 (CYP707A1/3), but neither overexpression of VIP1 nor truncation of its DNA-binding region affects the expression of CYP707A3 in vivo, raising the possibility that VIP and other proteins are functionally redundant. Here we show further analyses on VIP1 and its close homologs, namely, Arabidopsis group I bZIP proteins. The patterns of the signals of the GFP-fused group I bZIP proteins were similar in onion and Arabidopsis cells, suggesting that they have similar subcellular localization. In a yeast one-hybrid assay, the group I bZIP proteins caused reporter gene activation in the yeast reporter strain. VIP1 and other group I bZIP proteins showed positive results in a yeast two-hybrid assay and a bimolecular fluorescence complementation assay, suggesting that they physically interact. These results support the idea that they have somewhat similar functions. By gel shift assays, VIP1-binding sequences in the CYP707A1/3 promoters were confirmed to be AGCTGT/G. Their presence in the promoters of the genes that respond to hypo-osmotic conditions was evaluated using previously published microarray data. Interestingly, a significantly higher proportion of the promoters of the genes that were up-regulated by rehydration treatment and/or submergence treatment (treatment by a hypotonic solution) and a significantly lower proportion of the promoters of the genes that were down-regulated by such treatment shared AGCTGT/G. To further assess the physiological role of VIP1, constitutively nuclear-localized variants of VIP1 were generated. When overexpressed in Arabidopsis, some of them as well as VIP1 caused growth retardation under a mannitol-stressed condition, where VIP1 is localized mainly in the cytoplasm. This raises the possibility that the expression of VIP1 itself rather than its nuclear localization is responsible for regulating the mannitol responses
Detection, cloning and bioinformatics analysis of vip1/vip2 genes from local strains of Bacillus thuringiensis
No full textBio-insecticides based on the spore forming bacterium, Bacillus thuringiensis (Bt) have been used for commercial scale for the past 40 years. Bt is a Gram-positive soil bacterium that forms insecticidal crystal proteins (ICPs) during sporulation; it has been characterized as an insect pathogen. Vegetative insecticidal protein (VIP) is a newly discovered family of toxin protein isolated from Bt. A hundred strains of local Bacillus thuringiensis were isolated from soil and dead larvae, identified by 16S rRNA and screened for the presence of vip1 and vip2 genes by polymerase chain reaction (PCR) amplification, with only four strains producing the desired bands of Vip1 and Vip2. The amplified fragments were cloned in pGEM-vector, sequenced and analyzed. The nucleotide sequences of vip1 (2.3 kb) and vip2 (1.3 kb) were given Gene-bank accession numbers: JN008908 and JN035904, respectively. Vip1 and Vip2 showed 99% homology with the previously isolated genes.Key words: Bacillus thuringiensis, vegetative insecticidal proteins (vip1 and vip2), 16S rRNA, cloning
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