RESUMEN
Maize ear rot is a common disease found worldwide, caused by several toxigenic Fusarium species. Maize ears and kernels infected by Fusarium subglutinans contained significant amounts of beauvericin, fusaproliferin, moniliformin, and enniatins. In 2011, F. subglutinans sensu lato has been divided into two species: Fusarium temperatum sp. nov. and F. subglutinans sensu stricto, showing different phylogeny and beauvericin production within the populations of maize pathogens in Belgium. Isolates of the new species-F. temperatum-were also identified and characterized in Spain, Argentina, Poland, France, and China as one of the most important pathogens of maize. Moreover, F. temperatum was proved to be pathogenic to maize seedlings and stalks. We identified Fusarium isolates obtained from diseased maize ears collected between 2013 and 2016 in Poland (321 isolates). Based on morphological analyses, six Fusarium species were identified. Molecular identification performed on the set of selected isolates (42 isolates) revealed 34 isolates to be F. temperatum and only five to be F. subglutinans. Interestingly, the phylogenetic analysis showed that the population of F. temperatum infecting maize in Poland remained quite uniform for over 30 years with only a few exceptions. For the first time, a single isolate of Fusarium ramigenum was detected from the area of Poland. Significant amounts of BEA were found in Fusarium-damaged kernels. The same kernel samples contained also enniatins A1, A, B1, and B. The results clearly demonstrate the occurrence of F. temperatum as maize pathogen in Poland for over the last three decades.
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Fusarium/patogenicidad , Micotoxinas/análisis , Enfermedades de las Plantas/microbiología , Zea mays/microbiología , Ciclobutanos , Depsipéptidos , Fusarium/metabolismo , Filogenia , Polonia , TerpenosRESUMEN
Earlier studies demonstrate that when the frequency of rhythmic tone sequences or streams is task relevant, ongoing excitability fluctuations (oscillations) of neuronal ensembles in primary auditory cortex (A1) entrain to stimulation in a frequency dependent way that sharpens frequency tuning. The phase distribution across A1 neuronal ensembles at time points when attended stimuli are predicted to occur reflects the focus of attention along the spectral attribute of auditory stimuli. This study examined how neuronal activity is modulated if only the temporal features of rhythmic stimulus streams are relevant. We presented macaques with auditory clicks arranged in 33 Hz (gamma timescale) quintets, repeated at a 1.6 Hz (delta timescale) rate. Such multi-scale, hierarchically organized temporal structure is characteristic of vocalizations and other natural stimuli. Monkeys were required to detect and respond to deviations in the temporal pattern of gamma quintets. As expected, engagement in the auditory task resulted in the multi-scale entrainment of delta- and gamma-band neuronal oscillations across all of A1. Surprisingly, however, the phase-alignment, and thus, the physiological impact of entrainment differed across the tonotopic map in A1. In the region of 11-16 kHz representation, entrainment most often aligned high excitability oscillatory phases with task-relevant events in the input stream and thus resulted in response enhancement. In the remainder of the A1 sites, entrainment generally resulted in response suppression. Our data indicate that the suppressive effects were due to low excitability phase delta oscillatory entrainment and the phase amplitude coupling of delta and gamma oscillations. Regardless of the phase or frequency, entrainment appeared stronger in left A1, indicative of the hemispheric lateralization of auditory function.
RESUMEN
OBJECTIVE: The aim of this study was to evaluate the cognitive state of highly selected Polish centenarians and analyze the mechanisms of their functioning. METHODS: The selected centenarian group (10 persons) and a reference group (20 persons) who started aging (65 years) were examined with a sensitive set of neuropsychological tests and tasks in clinical-experimental assessment. RESULTS: As expected, the centenarians' cognitive functions were different from those of the subjects who started aging, however, not in all aspects. For instance, the former scored significantly lower in the area of linguistic functions but the ability to plan and controlled perform complex visuospatial task with use of simultaneous and sequential strategies was preserved despite unfavorable symptoms of natural aging such as permanence attention as well as prolonged action time. CONCLUSIONS: The results suggest that the studied centenarians show a dominant right-hemispheric pattern functioning not only in relation to perception, but also to planning and executing complex activities. The study and description of preserved neurocognition of centenarians was possible due to introducing a special procedure sensitive to the preserved functions.
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Envejecimiento/fisiología , Cognición/fisiología , Anciano , Anciano de 80 o más Años , Femenino , Evaluación Geriátrica/métodos , Humanos , Masculino , Persona de Mediana Edad , Pruebas Neuropsicológicas , PoloniaRESUMEN
BACKGROUND: Mild cognitive impairment (MCI) is a condition referring to the persons with cognitive deficits measurable in some form or another, but not meeting criteria for dementia, and who have an increased risk of becoming demented. OBJECTIVE: To establish the rate of progression to dementia in MCI, to investigate the risk of conversion for amnestic vs multiple-domains subtypes, and to identify the predictors of progression. METHODS: MCI (n = 105) individuals enrolled in a longitudinal study received annual clinical and psychometric examinations for up to a mean of 3 years. The diagnosis of MCI according to Mayo Clinic Petersen's Criteria was conducted by a panel of specialists. RESULTS: After 3 years of follow-up, 23 of 105 subjects with MCI were diagnosed with dementia. 40 showed cognitive decline not dementia, 34 were stable and showed no cognitive decline or improvement, while eight showed cognitive improvement. CONCLUSIONS: We conclude that conversion rate from MCI to DSM-IIIR dementia was 21.9% over a period of 3 years. The occurrence of depressive symptoms may constitute a predictor for those who are more likely to progress to dementia. The risk of conversion to dementia was higher among the subjects with an evidence of impairment extending beyond memory than with those who suffered only from memory deficits, and the subjects who converted to dementia in this subtype had significantly higher baseline plasma total homocysteine levels than non-converters.
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Enfermedad de Alzheimer/epidemiología , Trastornos del Conocimiento/epidemiología , Trastorno Depresivo/epidemiología , Anciano , Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/psicología , Trastornos del Conocimiento/diagnóstico , Trastornos del Conocimiento/psicología , Comorbilidad , Estudios Transversales , Trastorno Depresivo/diagnóstico , Trastorno Depresivo/psicología , Progresión de la Enfermedad , Femenino , Estudios de Seguimiento , Humanos , Masculino , Escala del Estado Mental , Persona de Mediana Edad , Polonia , Factores de RiesgoRESUMEN
OBJECTIVE: The aim of the study was to detect the prevalence of depressive syndromes and symptoms in the sample of elderly persons with Mild Cognitive Impairment (MCI), and to analyse Montgomery-Asberg Depression Rating (MADRS) item scores. METHOD: The subjects of the study were 102 consecutive out-patients with MCI. All subjects were assessed by an experienced psychiatrist and MADRS was applied. Major and minor depressive episodes were defined according to DSM-IV criteria. Factor analysis was used to analyse baseline MADRS item scores. RESULTS: Three patient groups emerged according to the depressive symptoms distribution and severity scores basis: those with major depression constituted 19.6% (n = 20), with minor depression 26.5% (n = 27), and with very few depressive symptoms 53.9% (n = 55). Three interpretable MADRS factors were identified, using the factor analysis with Varimax rotation: the first consisting of apparent and reported sadness, inability to feel, pessimistic thoughts, the second consisting of inner tension, reduced sleep, reduced appetite, suicidal thoughts, and the third with concentration difficulties and lassitude. CONCLUSIONS: It was concluded that both major and minor depression is common in MCI. Three MADRS factors were identified and labelled as anhedonia-pessimism, anxiety-vegetative, and cognitive-inhibition.
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Trastornos del Conocimiento/psicología , Depresión/diagnóstico , Trastorno Depresivo/diagnóstico , Anciano , Actitud Frente a la Muerte , Cognición , Depresión/psicología , Trastorno Depresivo/psicología , Femenino , Humanos , Masculino , Escalas de Valoración Psiquiátrica , Factores de Riesgo , Estrés PsicológicoRESUMEN
Potassium chloride (KCl)-depolarization has been used to study the properties of L-type Ca2+ channel-mediated signal transduction in hippocampal neurons. Calcium influx through L-type Ca2+ channels stimulates a second messenger pathway that transactivates genes under the regulatory control of the Ca2+-and cyclic AMP-responsive element (CRE). Here, we show that in striatal neurons, but not in hippocampal neurons, CRE binding protein (CREB) phosphorylation and CRE-mediated gene expression after KCl-depolarization depends on functional NMDA receptors. This difference in NMDA receptor dependence is not due to different properties of L-type Ca2+ channels in either neuronal type, but rather to different neuron-intrinsic properties. Despite this variation, the second messenger pathway activated by KCl requires Ca2+/calmodulin (CaM) kinase for CREB phosphorylation in both neuronal types. We conclude that depolarization by KCl works differently in striatal and hippocampal neurons.
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Cuerpo Estriado/metabolismo , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Potenciales de la Membrana/fisiología , Neuronas/metabolismo , Cloruro de Potasio/farmacología , Receptores de N-Metil-D-Aspartato/metabolismo , Animales , Agonistas de los Canales de Calcio/farmacología , Canales de Calcio Tipo L/efectos de los fármacos , Canales de Calcio Tipo L/metabolismo , Proteína Quinasa Tipo 1 Dependiente de Calcio Calmodulina , Proteínas Quinasas Dependientes de Calcio-Calmodulina/efectos de los fármacos , Proteínas Quinasas Dependientes de Calcio-Calmodulina/metabolismo , Células Cultivadas/efectos de los fármacos , Células Cultivadas/metabolismo , Cuerpo Estriado/efectos de los fármacos , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/efectos de los fármacos , Proteínas de Unión al ADN/efectos de los fármacos , Proteínas de Unión al ADN/metabolismo , Antagonistas de Aminoácidos Excitadores/farmacología , Feto , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/fisiología , Hipocampo/efectos de los fármacos , Hipocampo/metabolismo , Potenciales de la Membrana/efectos de los fármacos , Neuronas/efectos de los fármacos , Proteínas Nucleares/efectos de los fármacos , Proteínas Nucleares/metabolismo , Fosforilación/efectos de los fármacos , Pirroles/farmacología , Ratas , Receptores de GABA/efectos de los fármacos , Receptores de GABA/metabolismo , Receptores de N-Metil-D-Aspartato/efectos de los fármacos , Factor de Respuesta SéricaRESUMEN
The tumor necrosis factor alpha (TNF-alpha) gene is rapidly activated by lipopolysaccharide (LPS). Here, we show that extracellular signal-regulated kinase (ERK) kinase activity but not calcineurin phosphatase activity is required for LPS-stimulated TNF-alpha gene expression. In LPS-stimulated macrophages, the ERK substrates Ets and Elk-1 bind to the TNF-alpha promoter in vivo. Strikingly, Ets and Elk-1 bind to two TNF-alpha nuclear factor of activated T cells (NFAT)-binding sites, which are required for calcineurin and NFAT-dependent TNF-alpha gene expression in lymphocytes. The transcription factors ATF-2, c-jun, Egr-1, and Sp1 are also inducibly recruited to the TNF-alpha promoter in vivo, and the binding sites for each of these activators are required for LPS-stimulated TNF-alpha gene expression. Furthermore, assembly of the LPS-stimulated TNF-alpha enhancer complex is dependent upon the coactivator proteins CREB binding protein and p300. The finding that a distinct set of transcription factors associates with a fixed set of binding sites on the TNF-alpha promoter in response to LPS stimulation lends new insights into the mechanisms by which complex patterns of gene regulation are achieved.
Asunto(s)
Proteínas de Unión al ADN , Proteínas Nucleares/genética , Proteínas Proto-Oncogénicas/genética , Factor de Transcripción Sp1/genética , Transactivadores/genética , Factores de Transcripción/genética , Factor de Necrosis Tumoral alfa/genética , Animales , Secuencia de Bases , Proteína de Unión a CREB , Línea Celular , Elementos de Facilitación Genéticos , Regulación de la Expresión Génica/efectos de los fármacos , Lipopolisacáridos/farmacología , Datos de Secuencia Molecular , Regiones Promotoras Genéticas/genética , Proteínas Proto-Oncogénicas c-ets , Transducción de Señal/genética , Proteína Elk-1 con Dominio etsRESUMEN
The present study deals with the functional interaction of antipsychotic drugs and NMDA receptors. We show that both the conventional antipsychotic drug haloperidol and the atypical antipsychotic drug clozapine mediate gene expression via intracellular regulation of NMDA receptors, albeit to different extents. Data obtained in primary striatal culture demonstrate that the intraneuronal signal transduction pathway activated by haloperidol, the cAMP pathway, leads to phosphorylation of the NR1 subtype of the NMDA receptor at (897)Ser. Haloperidol treatment is likewise shown to increase (897)Ser-NR1 phosphorylation in rats in vivo. Mutation of (896)Ser and (897)Ser to alanine, which prevents phosphorylation at both sites, inhibits cAMP-mediated gene expression. We conclude that antipsychotic drugs have the ability to modulate NMDA receptor function by an intraneuronal signal transduction mechanism. This facilitation of NMDA activity is necessary for antipsychotic drug-mediated gene expression and may contribute to the therapeutic benefits as well as side effects of antipsychotic drug treatment.
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Antipsicóticos/farmacología , Receptores de N-Metil-D-Aspartato/efectos de los fármacos , Animales , Antipsicóticos/antagonistas & inhibidores , Northern Blotting , Células Cultivadas , Clozapina/antagonistas & inhibidores , Clozapina/farmacología , Cicloserina/farmacología , Maleato de Dizocilpina/farmacología , Agonistas de Aminoácidos Excitadores/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Regulación de la Expresión Génica/efectos de los fármacos , Genes fos/genética , Haloperidol/antagonistas & inhibidores , Haloperidol/farmacología , Masculino , Neostriado/efectos de los fármacos , Neostriado/metabolismo , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Fosforilación , Ratas , Ratas Sprague-Dawley , Receptores de N-Metil-D-Aspartato/biosíntesis , Receptores de N-Metil-D-Aspartato/genética , Transducción de Señal/efectos de los fármacosRESUMEN
The second messenger pathways linking receptor activation at the membrane to changes in the nucleus are just beginning to be unraveled in neurons. The work presented here attempts to identify in striatal neurons the pathways that mediate cAMP response element-binding protein (CREB) phosphorylation and gene expression in response to NMDA receptor activation. We investigated the phosphorylation of the transcription factor CREB, the expression of the immediate early gene c-fos, and the induction of a transfected reporter gene under the transcriptional control of CREB after stimulation of ionotropic glutamate receptors. We found that neither AMPA/kainate receptors nor NMDA receptors were able to stimulate independently a second messenger pathway that led to CREB phosphorylation or c-fos gene expression. Instead, we saw a consecutive pathway from AMPA/kainate receptors to NMDA receptors and from NMDA receptors to L-type Ca(2+) channels. AMPA/kainate receptors were involved in relieving the Mg(2+) block of NMDA receptors, and NMDA receptors triggered the opening of L-type Ca(2+) channels. The second messenger pathway that activates CREB phosphorylation and c-fos gene expression is likely activated by Ca(2+) entry through L-type Ca(2+) channels. We conclude that in primary striatal neurons glutamate-mediated signal transduction is dependent on functional L-type Ca(2+) channels.
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Canales de Calcio/fisiología , Cuerpo Estriado/fisiología , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Regulación de la Expresión Génica/fisiología , Ácido Glutámico/fisiología , Proteínas Proto-Oncogénicas c-fos/genética , Animales , Calcio/fisiología , Agonistas de los Canales de Calcio/farmacología , Canales de Calcio/genética , Canales de Calcio Tipo L , Cuerpo Estriado/citología , Cuerpo Estriado/efectos de los fármacos , Cuerpo Estriado/metabolismo , Magnesio/farmacología , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Neuronas/fisiología , Fosforilación , Proteínas Proto-Oncogénicas c-fos/metabolismo , Pirroles/farmacología , Ratas , Ratas Sprague-Dawley , Receptores AMPA/fisiología , Receptores de Glutamato/metabolismo , Receptores de Ácido Kaínico/fisiología , Receptores de N-Metil-D-Aspartato/antagonistas & inhibidores , Receptores de N-Metil-D-Aspartato/fisiología , Sodio/fisiologíaRESUMEN
N-Acetylated alpha-linked acidic dipeptidase (NAALADase) is a neuropeptidase that may modulate glutamatergic neurotransmission. Independent of its characterization in the nervous system, one form of NAALADase was shown to be expressed at high levels in human prostatic adenocarcinomas, and it was designated the prostate-specific membrane antigen (PSMA). The NAALADase/PSMA gene is known to produce multiple mRNA splice forms, and based on previous immunohistochemical evidence, it had been assumed that the human brain and prostate expressed different isoforms of the enzyme. Because PSMA is being actively pursued as a target for autoimmune and cytotoxic targeting strategies to treat prostate cancer, the rigorous comparison of the two forms of the enzyme remained an important but untested question. To assess similarities and/or differences between human brain NAALADase and PSMA, we compared the two molecules using criteria of activity, immunoreactivity and sequences of the corresponding mRNAs. NAALADase from human cerebellar isolates displayed a kinetic profile and pharmacological sensitivities similar to PSMA. Also, Northern hybridization to PSMA cDNA detected indistinguishable sets of 2.8-, 4.0- and 6.0-kb RNA species in human brain and the LNCaP prostatic tumor cell line. In addition, the monoclonal antibody 7E11-C5 directed against the prostatic form of the enzyme immunoprecipitated 82% of human cerebellar NAALADase activity. Moreover, reverse transcription-polymerase chain reaction cloning of cerebellar cDNAs indicated that the human brain and prostate express a common mRNA splice form. Therefore, we conclude that the form of NAALADase also known as PSMA is expressed in brain and comprises a significant fraction of brain NAALADase activity.
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Antígenos de Superficie/metabolismo , Encéfalo/enzimología , Carboxipeptidasas/metabolismo , Northern Blotting , Línea Celular , Clonación Molecular , Glutamato Carboxipeptidasa II , Humanos , Cinética , Reacción en Cadena de la Polimerasa , Pruebas de Precipitina , ARN Mensajero/biosíntesis , ARN Mensajero/químicaRESUMEN
Neuroplasticity serves an important role for normal striatal function and in disease states. One route to neuroplasticity involves activation of the transcription factor cyclic 3', 5'-adenosine monophosphate (cyclic AMP) response element binding protein (CREB) by phosphorylation of the amino acid 133Ser. Dopamine and glutamate, the two predominant neurotransmitters in the striatum, induce CREB phosphorylation in primary cultures of rat striatum through cyclic AMP and Ca2+ pathways. Here we present the role of N-methyl-D-aspartate receptors and Ca2+ in cyclic AMP-mediated CREB phosphorylation.
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Cuerpo Estriado/fisiología , AMP Cíclico/metabolismo , Plasticidad Neuronal/fisiología , Animales , Benzazepinas/farmacología , Calcio/fisiología , Colforsina/farmacología , Técnicas de Cultivo , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Maleato de Dizocilpina/farmacología , Dopamina/farmacología , Agonistas de Dopamina/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Fosforilación/efectos de los fármacos , Ratas/embriología , Ratas Sprague-Dawley , Receptores de N-Metil-D-Aspartato/fisiologíaRESUMEN
Glutamate carboxypeptidase II may modulate excitatory neurotransmission through the catabolism of the neuropeptide N-acetylaspartylglutamate (NAAG) and possibly other endogenous peptide substrates. To investigate the molecular properties of cloned human GCP II (hGCP II), we analyzed the NAAG-hydrolytic activity conveyed by transfection of a full-length hGCP II cDNA into PC3 cells, which do not express GCP II endogenously. Membrane fractions from these cells demonstrated activity with an apparent Km of 73 nM and Vmax of 35 pmol/(mg protein*min). Activity was inhibited by EDTA and stimulated by the addition of CoCl2. Addition of GCP II inhibitors beta-NAAG, quisqualic acid and 2-(phosphonomethyl)pentanedioic acid (PMPA) inhibited hydrolysis of 2.5 nM NAAG with IC50s of 201 nM, 155 nM and 98 pM, respectively. In competition experiments designed to infer aspects of hGCP II substrate selectivity, NAAG was the most potent alpha peptide tested, with an IC50 of 26 nM. Folate derivatives and some other gamma-glutamyl peptides showed comparable affinity to that of NAAG, also displaying IC50s in the low nM range. Taken together with previous evidence demonstrating their presence in GCP II-expressing tissues, these data suggest that both NAAG and folates are good candidate substrates for GCP II in vivo.
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Antígenos de Superficie , Carboxipeptidasas/metabolismo , Dipéptidos/metabolismo , Antagonistas de los Receptores Histamínicos H1/metabolismo , Neuropéptidos/metabolismo , Animales , Unión Competitiva/fisiología , Carboxipeptidasas/antagonistas & inhibidores , Carboxipeptidasas/genética , Quelantes/farmacología , Clonación Molecular , Cobalto/farmacología , Cumarinas/farmacología , Ácido Edético/farmacología , Ácido Fólico/análogos & derivados , Ácido Fólico/química , Glutamato Carboxipeptidasa II , Humanos , Hidrólisis , Isocumarinas , Cinética , Leucina/análogos & derivados , Leucina/farmacología , Masculino , Pepstatinas/farmacología , Fenantrolinas/farmacología , Neoplasias de la Próstata , Inhibidores de Proteasas/farmacología , Ratas , Inhibidores de Serina Proteinasa/farmacología , Especificidad por Sustrato , Transmisión Sináptica/fisiología , Células Tumorales Cultivadas/enzimologíaRESUMEN
N-acetylated alpha-linked acidic dipeptidase (NAALADase) hydrolyzes acidic peptides, such as the abundant neuropeptide N-acetyl-alpha-L-aspartyl-L-glutamate (NAAG), thereby generating glutamate. Previous cDNA cloning efforts have identified a candidate rat brain NAALADase partial cDNA, and Northern analyses have identified a family of related RNA species that are found only in brain and other NAALADase-expressing cells. In this report, we describe the cloning of a set of rat brain cDNAs that describe a full-length NAALADase mRNA. Transient transfection of a full-length cDNA into the PC3 cell line confers NAAG-hydrolyzing activity that is sensitive to the NAALADase inhibitors quisqualic acid and 2-(phosphonomethyl)glutaric acid. Northern hybridization detects the expression of three similar brain RNAs approximately 3,900, 3,000, and 2,800 nucleotides in length. In situ hybridization histochemistry shows that NAALADase-related mRNAs have an uneven regional distribution in rat brain and are expressed predominantly by astrocytes as demonstrated by their colocalization with the astrocyte-specific marker glial fibrillary acidic protein.
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Encéfalo/enzimología , Carboxipeptidasas/genética , Proteínas del Tejido Nervioso/genética , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Clonación Molecular , ADN Complementario/genética , Dipéptidos/metabolismo , Glutamato Carboxipeptidasa II , Hibridación in Situ , Datos de Secuencia Molecular , Neuropéptidos/metabolismo , Ratas , Proteínas Recombinantes , Análisis de Secuencia de ADN , Distribución TisularRESUMEN
Three mutations in the Arabidopsis thaliana gene encoding the alpha subunit of tryptophan synthase were isolated by selection for resistance to 5-methylanthranilate or 5-fluoroindole, toxic analogs of tryptophan pathway intermediates. Plants homozygous for trp3-1 and trp3-2 are light-conditional tryptophan auxotrophs, while trp3-100 is a more leaky mutant. Genetic complementation crosses demonstrated that the three mutations are allelic to each other, and define a new complementation group. All three mutants have decreased steady-state levels of tryptophan synthase alpha protein, and the trp3-100 polypeptide exhibits altered electrophoretic mobility. All three mutations were shown to be in the TSA1 (tryptophan synthase alpha subunit) structural gene by several criteria. Firstly, the trp3-1 mutation is linked to TSA1 on the bottom of chromosome 3. Secondly, the trp3-1 mutation was complemented when transformed with the wild-type TSA1 gene. Finally, DNA sequence analysis of the TSA1 gene revealed a single transition mutation in each trp3 mutant.
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Arabidopsis/enzimología , Mutación , Triptófano Sintasa/genética , Arabidopsis/genética , Mapeo Cromosómico , Fenotipo , Proteínas de Plantas/genética , Triptófano Sintasa/metabolismoRESUMEN
A study of the biochemical genetics of the Arabidopsis thaliana tryptophan synthase beta subunit was initiated by characterization of mutants resistant to the inhibitor 5-fluoroindole. Thirteen recessive mutations were recovered that are allelic to trp2-1, a mutation in the more highly expressed of duplicate tryptophan synthase beta subunit genes (TSB1). Ten of these mutations (trp2-2 through trp2-11) cause a tryptophan requirement (auxotrophs), whereas three (trp2-100 through trp2-102) remain tryptophan prototrophs. The mutations cause a variety of changes in tryptophan synthase beta expression. For example, two mutations (trp2-5 and trp2-8) cause dramatically reduced accumulation of TSB mRNA and immunologically detectable protein, whereas trp2-10 is associated with increased mRNA and protein. A correlation exists between the quantity of mutant beta and wild-type alpha subunit levels in the trp2 mutant plants, suggesting that the synthesis of these proteins is coordinated or that the quantity or structure of the beta subunit influences the stability of the alpha protein. The level of immunologically detectable anthranilate synthase alpha subunit protein is increased in the trp2 mutants, suggesting the possibility of regulation of anthranilate synthase levels in response to tryptophan limitation.