Auxin regulates a plethora of events during plant growth and development, acting in concert with other phytohormones. YUCCA genes encode flavin monooxygenases that function in tryptophan-dependent auxin biosynthesis. To understand the contribution of the YUCCA4 (YUC4) gene on auxin homeostasis, plant growth and interaction with abscisic acid (ABA) signaling, 35S::YUC4 seedlings were generated, which showed elongated hypocotyls with hyponastic leaves and changes in root system architecture that correlate with enhanced auxin responsive gene expression. Differential expression of PIN1, 2, 3 and 7 auxin transporters was detected in roots of YUC4 overexpressing seedlings compared to the wild-type: PIN1 was down-regulated whereas PIN2, PIN3 and PIN7 were up-regulated. Noteworthy, 35S::YUC4 lines showed enhanced sensitivity to ABA on seed germination and postembryonic root growth, involving ABI4 transcription factor. The auxin reporter genes DR5::GUS, DR5::GFP and BA3::GUS further revealed that abscisic acid impairs auxin responses in 35S::YUC4 seedlings. Our results indicate that YUC4 overexpression influences several aspects of auxin homeostasis and reveal the critical roles of ABI4 during auxin-ABA interaction in germination and primary root growth.
The post-embryonic growth of the Arabidopsis thaliana root system can be modified by different types of stress, such as sublethal concentrations of metals, which may induce the production of reactive oxygen species (ROS). In this study, the effects of different concentrations of potassium chromate (K₂CrO4) on the distribution and relative quantity of hydrogen peroxide (H2O2) were determined in primary and adventitious roots in A. thaliana HyPer line seedlings. This line has a biosensor that specifically reports H2O2 levels within tissues as fluorescence. Primary root growth was inhibited at 100 μM Cr (VI); in contrast, adventitious root formation was induced over the main root growth axis. These structures proliferated from 100-160 μM Cr (VI), and much higher concentrations (180-200 μM) of K₂CrO4 were required to affect their growth. The H2O2 distributions were observed in the columella and lateral root cap of primary roots of plants grown in medium lacking dichromate, but following the development of toxicity symptoms, H2O2 changed its distribution to the meristem and differentiation zones. Conversely, adventitious roots had comparable H2O2 distribution patterns in untreated plants and those exposed to Cr (VI) supplementation. Thus, differential H2O2 distribution correlates with the resistance of adventitious roots, but not primary roots, to dichromate and underlies cell reorganization at the apex to support growth.
Background: There is a clear association between obesity and Idiopathic Intracranial Hypertension (IIH), a syndrome characterized by increased Intracranial Pressure (ICP). The clinical manifestations of IHH include headache and visual/oculomotor disorders due to the involvement of abducens nerve. Thus far, it has not been widely studied whether affectations by ICP elevation could involve other cranial nerves such as the trigeminal nerve.Objective: The aim of this study is to analyze the prevalence of elevated ICP in patients with BMI ≥ 25 that suffer vascular compression of the trigeminal nerve. Methods: A case series including 19 patients evaluated during a period of 8 months with BMI ≥ 25 and a clinical diagnosis of classic trigeminal neuralgia (TN) who underwent Microvascular Decompression (MVD) surgery is reported. Patients with TN presenting another cause of intracranial hypertension were excluded. The ICP was determined just before MVD surgery by introducing an enteral tube through a 2 mm incision in the dura and measuring the level reached by the CSF. Results: In our series, 42.1% of patients suffered overweight (n = 8), 47.3% grade I obesity (n = 9) and 10.5% grade II obesity (n = 2). The ICP was elevated in 47.4% of patients. Conclusion: IHH is an obesity-related disorder. Patients with BMI ≥ 25 and TN show a high prevalence of ICP. It is important to consider that an obese patient may present high ICP during and after MVD surger
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