RESUMEN
Photorespiration is essential for the detoxification of glycolate and recycling of carbon to the Calvin Benson Bassham cycle. Enzymes participating in the pathway have been identified, and investigations now focus on the regulation of photorespiration by transporters and metabolites. However, regulation of photorespiration on the gene level has not been intensively studied. Here, we show that maximum transcript abundance of Glu:glyoxylate aminotransferase 1 (GGT1) is regulated by intron-mediated enhancement (IME) of the 5' leader intron rather than by regulatory elements in the 5' upstream region. The intron is rich in CT-stretches and contains the motif TGTGATTTG that is highly similar to the IME-related motif TTNGATYTG. The GGT1 intron also confers leaf-specific expression of foreign promoters. Quantitative PCR analysis and GUS activity measurements revealed that IME of the GGT1 5'UTR intron is controlled on the transcriptional level. IME by the GGT1 5'UTR intron was at least 2-fold. Chromatin immunoprecipitation experiments showed that the abundance of RNA polymerase II binding to the intron-less construct is reduced.
Asunto(s)
Regiones no Traducidas 5'/genética , Regulación de la Expresión Génica de las Plantas , Intrones/genética , Regiones Promotoras Genéticas/genética , ARN Polimerasa II/metabolismo , Transaminasas/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Secuencia de Bases , Sitios de Unión/genética , Motivos de Nucleótidos/genética , Hojas de la Planta/genética , Hojas de la Planta/metabolismo , Plantas Modificadas Genéticamente , Unión Proteica , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Homología de Secuencia de Ácido Nucleico , Transcripción GenéticaRESUMEN
This paper investigates if the highly selective norepinephrine reuptake inhibitor reboxetine leads to a dose-dependent cortisol release and if this response depends on personality dimensions related to clinical depression in healthy volunteers. Twenty-four male subjects received placebo, 2 mg, or 4 mg reboxetine in a balanced, randomized cross-over study. Cortisol was measured in saliva at six different time-points according to the kinetics of the drug. Furthermore, several measurements of cardiovascular parameters, emotional states, and possible side-effects were obtained. Subjects were divided into two groups scoring above or below the median of a depressiveness questionnaire scale [n = 11, low (D-); n = 13, high (D+)]. Results clearly demonstrated, that reboxetine stimulates cortisol release. Whereas blood pressure was not affected, heart rate increased after 2 and 4 mg but not dose dependently. Subjects reported more non-specific arousal while the dimensions of tiredness-wakefulness and positive-negative emotional states were not affected by the drug. Somatic complaints were low and only non-specific complaints were statistically elevated but of negligible amount. Subjects classified as D+ can be characterized as high responders to the drug. This is especially true not only for cortisol increases but also for changes in heart rate and some ratings on physical complaints. Hot flushes, sweating and a throbbing sensation in blood vessels in the head were observed in D+ but only with the 4 mg dose. The results clearly demonstrate that reboxetine stimulates cortisol release and heart rate and that this is particularly pronounced in subjects scoring high on depression-related personality dimensions. Reboxetine, therefore, is a promising tool for investigating neuroendocrine response to noradrenergic challenge tests. The question whether increased responses in D+ are due to an up-regulation of receptor sensitivity as a consequence of low norepinephrine supply is discussed.