Extensin-like Glycoproteins in the Maize Pollen Tube Wall.

We recently described the cloning and characterization of Pex1, a maize pollen-specific gene with an extensin-like domain. Here, we report that antibodies raised against a Pex fusion protein and a Pex synthetic peptide recognize a protein doublet with an apparent molecular mass of ~300 kD as well as larger proteins in pollen extracts. These proteins were not detected in extracts of seedling, endosperm, ear, silk, root, leaf, wounded leaf, meiotic tassel, or young microspore. After deglycosylation, only the protein doublet was detected by the anti-Pex antiserum, suggesting that the higher molecular mass proteins represent a glycosylated form of the Pex proteins. The anti-Pex antiserum was also used in immunolocalization experiments with in vitro-germinated pollen. With the aid of a confocal light microscope, the Pex proteins were localized to the pollen tube wall. The Pex proteins could not be removed with high salt, SDS, or chaotropic or reducing agents, suggesting a very tight association with the pollen tube wall. Immunocytochemical analysis at the ultrastructural level localized the Pex proteins to the intine in mature pollen and to the callosic sheath of the pollen tube wall in germinated pollen. Localization to the pollen tube wall strongly suggests that the Pex proteins play a role in pollen tube growth during pollination.

Determinants and geographical variation in the distribution of depression in the Southern cone of Latin America: A population-based survey in four cities in Argentina, Chile and Uruguay.

BACKGROUND: Depression is one of the major contributors to the global burden of diseases; however, population-based data in South America are limited. METHODS: We conducted a population-based cross sectional study with 7524 participants, aged 35-74 years old, recruited between February 2010 and December 2011 from randomly selected samples in 4 cities (Bariloche and Marcos Paz, Argentina; Temuco, Chile; and Pando-Barros Blancos, Uruguay). Major Depressive Episode (MDE) was assessed using the Patient Health Questionnaire (PHQ) - 9. RESULTS: The overall prevalence of MDE was 14.6% (95% CI: 13.6, 15.6). However, there was a geographical variability of up to 3.7 folds between different cities being 5.6% (95% CI: 4.6, 6.7) in Marcos Paz, Argentina; 9.5% (95% CI: 8.2, 10.9) in Bariloche, Argentina; 18.1% (95% CI: 16.3, 20.0) in Temuco, Chile, and 18.2 (95% CI: 16.3, 20.2) in Pando-Barros Blancos, Uruguay. The multivariate model showed that, adjusted by location, being female, being between 35 and 44 years old, having experienced at least one stressful life event, currently smoking, and having a history of chronic medical diseases were independently associated with an increased risk of MDE, while having higher education and being married or living with a partner reduced the risk of MDE. LIMITATIONS: These results are representative of the selected cities included in the study. As such extrapolation to the general populations of Argentina, Chile, and Uruguay should be done with caution CONCLUSIONS: This study showed a high prevalence and variability of MDE in the Southern Cone of Latin America.

Zea mI, the maize homolog of the allergen-encoding Lol pI gene of rye grass.

Sequence analysis of a pollen-specific cDNA from maize has identified a homolog (Zea mI) of the gene (Lol pI) encoding the major allergen of rye-grass pollen. The protein encoded by the partial cDNA sequence is 59.3% identical and 72.7% similar to the comparable region of the reported amino acid sequence of Lol pIA. Southern analysis indicates that this cDNA represents a member of a small multigene family in maize. Northern analysis shows expression only in pollen, not in vegetative or female floral tissues. The timing of expression is developmentally regulated, occurring at a low level prior to the first pollen mitosis and at a high level after this postmeiotic division. Western analysis detects a protein in maize pollen lysates using polyclonal antiserum and monoclonal antibodies directed against purified Lolium perenne allergen.

Pex1, a pollen-specific gene with an extensin-like domain.

We report here the identification of a pollen-specific gene from Zea mays that contains multiple Ser-(Pro)n repeats, the motif found in the cell wall-associated extensins. Sequence analysis reveals that the encoded protein has a putative globular domain at the N terminus and an extensin-like domain at the C terminus. The Pex1 (pollen extensin-like) gene is expressed exclusively in pollen, not in vegetative or female tissues, and is not induced in leaves upon wounding. We propose that the encoded protein may have a role in reproduction, either as a structural element deposited in the pollen tube wall during its rapid growth or as a sexual recognition molecule that interacts with partner molecules in the pistil.

Genes dependent on zebrafish cyclops function identified by AFLP differential gene expression screen.

Zebrafish cyclops (cyc) encodes a Transforming Growth Factor beta (TGFbeta) signaling factor closely related to mouse Nodal. By comparing amplified fragment length polymorphisms (AFLP) from cyc mutant and wild-type cDNA pools, we devised a differential gene expression screen to isolate genes whose expression is dependent on Cyc signaling. We report two genes not previously described in the zebrafish that were identified using this approach. The first gene, crestin, is expressed predominantly in premigratory and migrating neural crest cells during somitogenesis stages. crestin expression is reduced in cyc mutants initially but recovers by late somitogenesis. The second gene encodes the zebrafish homologue of the calcium-binding protein, calreticulin. Zebrafish calreticulin is highly expressed in the hatching gland and in the floor plate, tissues that are affected in cyc mutants. During gastrulation, calreticulin transcripts are found in the dorsal mesendoderm, in the same cells that express the cyc gene. Expression is reduced in cyc mutants and is abolished by the one-eyed pinhead (oep) mutation that is presumed to prevent Nodal signaling. The identification of calreticulin suggests that a differential screen between wild-type and mutant cDNA is a useful approach to reveal regulation of unexpected gene expression in response to cellular signals. genesis 26:86-97, 2000.

Induction of the zebrafish ventral brain and floorplate requires cyclops/nodal signalling.

Zebrafish cyclops (cyc) mutations cause deficiencies in the dorsal mesendoderm and ventral neural tube, leading to neural defects and cyclopia. Here we report that cyc encodes a transforming growth factor-beta (TGF-beta)-related intercellular signalling molecule that is similar to mouse nodal. cyc is expressed in dorsal mesendoderm at gastrulation and in the prechordal plate until early somitogenesis. Expression reappears transiently in the left lateral-plate mesoderm, and in an unprecedented asymmetric pattern in the left forebrain. Injection of cyc RNA non-autonomously restores sonic hedgehog-expressing cells of the ventral brain and floorplate that are absent in cyc mutants, whereas inducing activities are abolished by cyc, a mutation of a conserved cysteine in the mature ligand. Our results indicate that cyc provides an essential non-cell-autonomous signal at gastrulation, leading to induction of the floorplate and ventral brain.

Asymmetric nodal signaling in the zebrafish diencephalon positions the pineal organ.

The vertebrate brain develops from a bilaterally symmetric neural tube but later displays profound anatomical and functional asymmetries. Despite considerable progress in deciphering mechanisms of visceral organ laterality, the genetic pathways regulating brain asymmetries are unknown. In zebrafish, genes implicated in laterality of the viscera (cyclops/nodal, antivin/lefty and pitx2) are coexpressed on the left side of the embryonic dorsal diencephalon, within a region corresponding to the presumptive epiphysis or pineal organ. Asymmetric gene expression in the brain requires an intact midline and Nodal-related factors. RNA-mediated rescue of mutants defective in Nodal signaling corrects tissue patterning at gastrulation, but fails to restore left-sided gene expression in the diencephalon. Such embryos develop into viable adults with seemingly normal brain morphology. However, the pineal organ, which typically emanates at a left-to-medial site from the dorsal diencephalic roof, becomes displaced in position. Thus, a conserved signaling pathway regulating visceral laterality also underlies an anatomical asymmetry of the zebrafish forebrain.