Natural variation in iron use efficiency and mineral remobilization in cucumber (Cucumis sativus)

Aims

Iron (Fe) is an essential micronutrient, and plant available Fe is often limited in alkaline soils. Fe deficiency chlorosis decreases plant growth and yield. Identification of germplasm with high and low Fe use efficiency will allow studies to better understand the genetic components for breeding Fe efficient varieties.

Methods

A screen using cucumber (Cucumis sativus) seedlings identified varieties that maintained contrasting levels of chlorophyll under Fe deficiency or limitation. A time course of mineral dynamics in cotyledons was conducted.

Results

The variety Ashley had the highest chlorophyll under Fe deficiency and per unit Fe in the leaf, while the variety Miniature White had the lowest. Ashley also maintained higher chlorophyll when challenged with low Fe or bicarbonate, accumulated greater quantities of Fe, and had higher root ferric reductase activity. Cotyledons accumulated minerals for the first several days, then Fe, P, K, and Cu were remobilized. The Fe use efficient and inefficient varieties remobilized Fe and P on different timescales.

Conclusions

Our results suggest that this screen can identify varieties for systems level studies that could elucidate factors needed for Fe use efficiency and remobilization of minerals. The time course indicated that cotyledon Fe stores did not contribute to seedling Fe use efficiency.     

Characterization of the <Emphasis Type="Italic">Trichomonas vaginalis</Emphasis> surface-associated AP65 and binding domain interacting with trichomonads and host cells

Background  

AP65 is a prominent adhesin of Trichomonas vaginalis that mediates binding of parasites to host vaginal epithelial cells (VECs). AP65 with no secretion signal sequence, membrane targeting peptide, and anchoring motif was recently found to be secreted.     

Impacts of inbreeding on bumblebee colony fitness under field conditions

Background  

Inbreeding and the loss of genetic diversity are known to be significant threats to small, isolated populations. Hymenoptera represent a special case regarding the impact of inbreeding. Haplodiploidy may permit purging of deleterious recessive alleles in haploid males, meaning inbreeding depression is reduced relative to diploid species. In contrast, the impact of inbreeding may be exacerbated in Hymenopteran species that have a single-locus complementary sex determination system, due to the production of sterile or inviable diploid males. We investigated the costs of brother-sister mating in the bumblebee Bombus terrestris. We compared inbred colonies that produced diploid males and inbred colonies that did not produce diploid males with outbred colonies. Mating, hibernation and colony founding took place in the laboratory. Once colonies had produced 15 offspring they were placed in the field and left to forage under natural conditions.     

Genetic identity and differential gene expression between Trichomonas vaginalis and Trichomonas tenax

Background  

Trichomonas vaginalis is a human urogenital pathogen responsible for trichomonosis, the number-one, non-viral sexually transmitted disease (STD) worldwide, while T. tenax is a commensal of the human oral cavity, found particularly in patients with poor oral hygiene and advanced periodontal disease. The extent of genetic identity between T. vaginalis and its oral commensal counterpart is unknown.     

N-acetylglucosaminyltranferase VB expression enhances beta1 integrin- dependent PC12 neurite outgrowth on laminin and collagen

N-acetylglucosaminyltransferase VB (GnT-VB, -IX) is a newly discovered glycosyltransferase expressed exclusively in high levels in neuronal tissue during early development. Its homolog, GnT-V, is expressed in many tissues and modulates cell-cell and cell-matrix adhesion. The ability of GnT-VB to regulate cell-matrix interactions was initially investigated using the rat pheochromocytoma PC12 neurite outgrowth model. PC12 cells stably transfected with GnT-VB consistently showed an enhanced rate of nerve growth factor (NGF)-induced neurite outgrowth on collagen and laminin substrates. Levels of TrkA receptor phosphorylation and downstream ERK activation induced by NGF were not influenced by GnT-VB expression. No significant difference was observed in the rate of neurite outgrowth when cells were cultured on non-coated culture dishes, indicating that integrin-ECM interaction is required for the stimulatory effects. Neurite outgrowth induced by manganese-dependent activation of beta1 integrin on collagen and laminin substrates, however, showed a significant increase in neurite length for the PC12/GnT-VB cells, compared with control cells, suggesting that the enhancement is most likely mediated by alteration of beta1 integrin-ECM interaction by GnT-VB. These results demonstrate that GnT-VB expression can modulate the rate of neurite outgrowth by affecting beta1 integrin-ECM interaction.     

Early origin of foraminifera suggested by SSU rRNA gene sequences

Foraminifera are one of the largest groups of unicellular eukaryotes with probably the best known fossil record. However, the origin of foraminifera and their phylogenetic relationships with other eukaryotes are not well established. In particular, two recent reports, based on ribosomal RNA gene sequences, have reached strikingly different conclusions about foraminifera's evolutionary position within eukaryotes. Here, we present the complete small subunit (SSU) rRNA gene sequences of three species of foraminifera. Phylogenetic analysis of these sequences indicates that they branch very deeply in the eukaryotic evolutionary tree: later than those of the amitochondrial Archezoa, but earlier than those of the Euglenozoa and other mitochondria-bearing phyla. Foraminifera are clearly among the earliest eukaryotes with mitochondria, but because of the peculiar nature of their SSU genes we cannot be certain that they diverged first, as our data suggest.      

Expression of N-linked sialyl Le(x) determinants and O-glycans in the carbohydrate moiety of human amniotic fluid transferrin during pregnancy

Transferrin, a glycoprotein involved in iron transport in body fluids, was isolated from amniotic fluid of a hydramniospatient by sequential anion-exchange chromatography and gel filtration. The N-glycans of human amniotic fluid transferrin (hAFT) were enzymatically liberated by PNGase-F digestion, isolated by gel filtration and fractionated by (high-pH) anion-exchange chromatography. After alkaline borohydride treatment of native hAFT, the released O-glycans were isolated by gel filtration and fractionated by anion-exchange chroma-tography. Structure elucidation of 14 N- and 2 O-glycans was performed by 500 or 600 MHz1H-NMR spectroscopy. Besides conventional N-glycans established earlier for human serum transferrin (hST), new (alpha1-3)-fucosylated N- glycans were found, representing sialyl Le(x) elements. Furthermore, as compared to hST, a higher degree of (alpha1-6)-fucosylation and an increase in branching from di- to triantennary compounds has been detected. The presence of O-glycans is demonstrated for the first time in transferrin.