A bacterial artificial chromosome (BAC) genomic approach reveals partial clustering of the furanocoumarin pathway genes in parsnip.

Furanocoumarins are specialized metabolites that are involved in the defense of plants against phytophagous insects. The molecular and functional characterization of the genes involved in their biosynthetic pathway is only partially complete. Many recent reports have described gene clusters responsible for the biosynthesis of specialized metabolites in plants. To investigate possible co-localization of the genes involved in the furanocoumarin pathway, we sequenced parsnip BAC clones spanning two different gene loci. We found that two genes previously identified in this pathway, CYP71AJ3 and CYP71AJ4, were located on the same BAC, whereas a third gene, PsPT1, belonged to a different BAC clone. Chromosome mapping using fluorescence in situ hybridization (FISH) indicated that PsPT1 and the CYP71AJ3-CYP71AJ4 clusters are located on two different chromosomes. Sequencing the BAC clone harboring PsPT1 led to the identification of a gene encoding an Fe(II) α-ketoglutarate-dependent dioxygenase (PsDIOX) situated in the neighborhood of PsPT1 and confirmed the occurrence of a second gene cluster involved in the furanocoumarin pathway. This enzyme metabolizes p-coumaroyl CoA, leading exclusively to the synthesis of umbelliferone, an important intermediate compound in furanocoumarin synthesis. This work provides an insight into the genomic organization of genes from the furanocoumarin biosynthesis pathway organized in more than one gene cluster. It also confirms that the screening of a genomic library and the sequencing of BAC clones represent a valuable tool to identify genes involved in biosynthetic pathways dedicated to specialized metabolite synthesis.

Spin-Dependent Transport in Fe/GaAs(100)/Fe Vertical Spin-Valves.

The integration of magnetic materials with semiconductors will lead to the development of the next spintronics devices such as spin field effect transistor (SFET), which is capable of both data storage and processing. While the fabrication and transport studies of lateral SFET have attracted greatly attentions, there are only few studies of vertical devices, which may offer the opportunity for the future three-dimensional integration. Here, we provide evidence of two-terminal electrical spin injection and detection in Fe/GaAs/Fe vertical spin-valves (SVs) with the GaAs layer of 50 nanometers thick and top and bottom Fe electrodes deposited by molecular beam epitaxy. The spin-valve effect, which corresponds to the individual switching of the top and bottom Fe layers, is bias dependent and observed up to 20 K. We propose that the strongly bias- and temperature-dependent MR is associated with spin transport at the interfacial Fe/GaAs Schottky contacts and in the GaAs membranes, where balance between the barrier profiles as well as the dwell time to spin lifetime ratio are crucial factors for determining the device operations. The demonstration of the fabrication and spin injection in the vertical SV with a semiconductor interlayer is expected to open a new avenue in exploring the SFET.

Lymphocytic hypophysitis occurring simultaneously with a functioning pituitary adenoma.

Lymphocytic Hypophysitis (LH) is a rare and previously under-recognised disorder, most commonly affecting young females in the post-partum period. It presents clinically with symptoms and signs related to either a pituitary mass or hypopituitarism, frequently mimicking a pituitary adenoma; the diagnosis of LH can only be made histologically with the presence of a dense lymphocytic infiltration usually confined to the anterior pituitary. We present two case histories of patients who presented with symptoms suggestive of a functioning pituitary adenoma who also had concomitant LH confirmed histologically. The first case was a 39 year old lady, with a history of primary hypothyroidism, who presented with weight gain and hirsutism and clinical and biochemical features of Cushing's syndrome. The second case was a 61 year old male, also with a history of primary hypothyroidism, who presented with visual field loss and biochemically with hyperprolactinaemia. In both patients, magnetic resonance (MR) imaging of the pituitary demonstrated an enlarged partially cystic pituitary mass with slight suprasellar extension. Both patients were treated surgically with transphenoidal drainage and excision and histological examination of the surgical specimens demonstrated a mixture of pathologies with fragments of adenohypophyseal tissue (staining positive for ACTH and prolactin respectively) with a dense chronic inflammatory cell infiltrate suggestive of LH in nearby normal anterior pituitary. In both cases a joint diagnosis of a functioning pituitary adenoma with LH was made. There have been only several reported cases of this combination of pathologies but LH even in isolation is becoming increasingly recognised.