The soybean ENOD40(2) promoter is active in Arabidopsis thaliana and is temporally and spatially regulated

The ENOD40 gene is induced early during Rhizobium-legume symbiosis and has probably a primary role in the nodule organogenesis. In this paper we show that the 1.7 kb 5-flanking region of the GmENOD40(2) is able to drive the expression of a gusA-int marker in transgenic Arabidopsis thaliana. The promoter activity is developmentally regulated and the major activity is detected in the root and in the stigma.     

Growth signalling pathways in Arabidopsis and the AGC protein kinases

Lipid-derived signals are central to regulating a multitude of cellular processes but, in plants, little is known of the downstream signalling pathways. The Arabidopsis 3-phosphoinositide-dependent protein kinase (PDK1) could couple lipid signals to the activation of several protein kinases of the so-called AGC kinase family. The Arabidopsis AGC kinases contain sequence motives required for the docking of PDK1 and phosphorylation of their activation loop in the kinase catalytic domain. It is becoming evident that specific members of the AGC kinases are implicated in key growth signalling pathways. For example, Arabidopsis p70(S6K) might be a nodal point able to integrate hormonal and developmental signals with nutritional inputs, together with the Arabidopsis Target of Rapamycin (TOR) protein.     

Male infertility,impaired sperm motility,and hydrocephalus in mice deficient in sperm-associated antigen 6

Gene targeting was used to create mice lacking sperm-associated antigen 6 (Spag6), the murine orthologue of Chlamydomonas PF16, an axonemal protein containing eight armadillo repeats predicted to be important for flagellar motility and stability of the axoneme central apparatus. Within 8 weeks of birth, approximately 50% of Spag6-deficient animals died with hydrocephalus. Spag6-deficient males surviving to maturity were infertile. Their sperm had marked motility defects and was morphologically abnormal with frequent loss of the sperm head and disorganization of flagellar structures, including loss of the central pair of microtubules and disorganization of the outer dense fibers and fibrous sheath. We conclude that Spag6 is essential for sperm flagellar motility and that it is important for the maintenance of the structural integrity of mature sperm. The occurrence of hydrocephalus in the mutant mice also implicates Spag6 in the motility of ependymal cilia.     

Serous cutaneous glands in new world hylid frogs: an ultrastructural study on skin poisons confirms phylogenetic relationships between Osteopilus septentrionalis and Phrynohyas venulosa

Transmission electron microscope investigations of the serous (poison) skin glands in the New World tree frogs Osteopilus septentrionalis and Phrynohyas venulosa revealed that they produce granules with closely similar substructures, namely, a dense cortex and pale medulla. In both species these features, that contrast the complex, sometimes repeating patterns described in other hylid frogs, derive from similar secretory and maturational processes starting from the Golgi phase of poison biosynthesis. Observations on secretory discharge showed that the two species share common release mechanisms, based on bulk discharge (holocrine) processes. Our data provide novel evidence of the extensive ultrastructural polymorphism of serous skin products in Hylidae and agree with phylogenies that regard this family as polyphyletic in origin. Assuming that ultrastructural features of cutaneous poison biosynthesis and maturation are adequate clues for tracking anuran phylogeny, the present findings also support a close relationship between Osteopilus and Phrynohyas taxa as previously suggested by osteological evidence.     

Two-way arginine transport in human endothelial cells: TNF-alpha stimulation is restricted to system y+

Humanumbilical vein endothelial cells transport arginine through twoNa⁺-independent systems. System y⁺L isinsensitive to N-ethylmaleimide (NEM), inhibited byL-leucine in the presence of Na⁺, and referableto the expression of SLC7A6/y⁺LAT2,SLC7A7/y⁺LAT1, and SLC3A2/4F2hc. System y⁺ isreferable to the expression of SLC7A1/CAT1 and SLC7A2/CAT2B. Tumornecrosis factor- (TNF-) and bacterial lipopolysaccharide induce atransient stimulation of arginine influx and efflux through systemy⁺. Increased expression of SLC7A2/CAT2B is detectable from3 h of treatment, while SLC7A1 expression is inhibited at latertimes of incubation. System y⁺L activity and expressionremain unaltered. Nitric oxide synthase type 2 mRNA is not detected inthe absence or presence of TNF-, while the latter condition lowersnitric oxide synthase type 3 expression at the mRNA and the proteinlevel. Nitrite accumulation is comparable in cytokine-treated andcontrol cells up to 48 h of treatment. It is concluded thatmodulation of endothelial arginine transport by TNF- orlipopolysaccharide occurs exclusively through changes in CAT2B and CAT1expression and is dissociated from stimulation of nitric oxide production.

     

Insulin/insulin-like growth factor I hybrid receptors have different biological characteristics depending on the insulin receptor isoform involved

The insulin receptor (IR) and the insulin-like growth factor I receptor (IGF-IR) have a highly homologous structure, but different biological effects. Insulin and IGF-I half-receptors can heterodimerize, leading to the formation of insulin/IGF-I hybrid receptors (Hybrid-Rs) that bind IGF-I with high affinity. As the IR exists in two isoforms (IR-A and IR-B), we evaluated whether the assembly of the IGF-IR with either IR-A or IR-B moieties may differently affect Hybrid-R signaling and biological role. Three different models were studied: (a) 3T3-like mouse fibroblasts with a disrupted IGF-IR gene (R(-) cells) cotransfected with the human IGF-IR and with either the IR-A or IR-B cDNA; (b) a panel of human cell lines variably expressing the two IR isoforms; and (c) HepG2 human hepatoblastoma cells predominantly expressing either IR-A or IR-B, depending on their differentiation state. We found that Hybrid-Rs containing IR-A (Hybrid-Rs(A)) bound to and were activated by IGF-I, IGF-II, and insulin. By binding to Hybrid-Rs(A), insulin activated the IGF-I half-receptor beta-subunit and the IGF-IR-specific substrate CrkII. In contrast, Hybrid-Rs(B) bound to and were activated with high affinity by IGF-I, with low affinity by IGF-II, and insignificantly by insulin. As a consequence, cell proliferation and migration in response to both insulin and IGFs were more effectively stimulated in Hybrid-R(A)-containing cells than in Hybrid-R(B)-containing cells. The relative abundance of IR isoforms therefore affects IGF system activation through Hybrid-Rs, with important consequences for tissue-specific responses to both insulin and IGFs.     

Cutting edge: TCR engagement and triggering in the absence of large-scale molecular segregation at the T cell-APC contact site

We investigated the functional role of large-scale molecular segregation at the T cell-APC contact site during T lymphocyte Ag recognition. Inhibition of CD2-CD58 interaction markedly affected segregation of CD2 and CD2AP from CD45. Under these conditions, Ag-induced calcium mobilization, PKC theta; clustering at the immunological synapse, and IFN-gamma production also were inhibited. However, early TCR signaling and T cell polarization toward APCs were unaffected. Our results indicate that the "raison d'être" of a large-scale segregation of surface molecules and intracellular enzymes and adapters, in Ag-stimulated T cells, is to reinforce the assembly of the signal transduction cascade rather than favor TCR engagement and triggering.     

Keratinocytes enriched for stem cells are protected from anoikis via an integrin signaling pathway in a Bcl-2 dependent manner

In zebrafish, the basic helix-loop-helix (bHLH) gene neuroD specifies distinct neurons in the spinal cord. A preliminary experiment indicated that a related bHLH gene, ndr1a, normally expressed only in the olfactory organ in late embryos, also functions as neuroD to induce ectopic formation of spinal cord neurons in early embryos after introduction of its mRNA into early embryos. To define the functional specificity of these bHLH proteins, several mutant forms with selected point mutations in the basic domain were constructed and tested for inducing sensory neurons in the spinal cord. Our data indicate that the functional specificity of NeuroD to define sensory neurons is mainly due to a single residue (asparagine 11) in its basic domain.