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Auxin is a class of plant hormone that plays a crucial role in the life cycle of plants, particularly in the growth response of plants to ever-changing environments. Since the auxin responses are concentration-dependent and higher auxin concentrations might often be inhibitory, the optimal endogenous auxin level must be closely controlled. However, the underlying mechanism governing auxin homeostasis remains largely unknown. In this study, a UDP-glycosyltransferase (UGT76F1) was identified from Arabidopsis thaliana, which participates in the regulation of auxin homeostasis by glucosylation of indole-3-pyruvic acid (IPyA), a major precursor of the auxin indole-3-acetic acid (IAA) biosynthesis, in the formation of IPyA glucose conjugates (IPyA-Glc). In addition, UGT76F1 was found to mediate hypocotyl growth by modulating active auxin levels in a light- and temperature-dependent manner. Moreover, the transcription of UGT76F1 was demonstrated to be directly and negatively regulated by PIF4, which is a key integrator of both light and temperature signaling pathways. This study sheds a light on the trade-off between IAA biosynthesis and IPyA-Glc formation in controlling auxin levels and reveals a regulatory mechanism for plant growth adaptation to environmental changes through glucosylation of IPyA. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the utility of three-dimensional computed tomographic angiography (3D-CTA) as the primary diagnostic investigation in patients with spontaneous subarachnoid haemorrhage (SAH) from anterior circulation aneurysms, and to correlate the results with digital subtraction angiography (DSA) and intraoperative findings. From May 2005 to May 2007 a total of 38 consecutive patients admitted for SAH, suspicious for ruptured anterior circulation cerebral aneurysm, underwent 3D-CTA. Inclusion criteria were a SAH confirmed by a non-contrast head computed tomographic scan or by lumbar puncture. Exclusion criteria were: previous DSA, severe contrast medium allergy and severe renal failure. All patients underwent early surgical clipping of the aneurysm. The mean time between SAH onset and surgery was 43.6 h (range, 14-74 h). The 3D-CTA was performed in all cases; and in 13 out of 38 patients (34%) represented the only preoperative exam. In all patients that underwent surgery with the sole 3D-CTA, the images collected allowed a good visualisation of the morphology of aneurysms and of the anatomical relationship with the vascular structures. 3D-CTA allows accurate diagnosis with an excellent visualisation of ruptured aneurysms of the anterior circulation. Our results suggest that, in selected cases, ruptured anterior circulation aneurysms could be successfully treated on the basis of 3D-CTA alone. [ABSTRACT FROM AUTHOR]