Cytological analysis of hybrids among triticales and trigopiros

WE STUDIED THREE DIFFERENT TRICEPIROS: (Don Santiago x Don Noé), (Cumé x Horovitz) and (Cumé x Don Noé). The tricepiro (Don Santiago x Don Noé) was obtained by crossing the triticale Don Santiago INTA (AABBRR, 2n = 6x = 42) with the trigopiro Don Noé INTA (AABBDDJJ, 2n = 8x = 56). The number of chromosomes for the F(1) was 2n = 49, the most frequent meiotic configuration being 14 bivalents and 21 univalents. The univalents were situated in the periphery of the equatorial plane, whereas the bivalents were located in the central zone. The chromatids in some of the univalents split when bivalents underwent reductional division in anaphase I. There were few laggard chromosomes or chromatids at this phase. The number of chromosomes (2n = 48-58) was high and variable, and the number of bivalents per cell (18-23) also high in F (3) individuals. In all F (8) tricepiros (Don Santiago x Don Noé), F (12) tricepiros (Cumé x Horovitz) and F (12) tricepiros (Cumé x Don Noé), the number of chromosomes (2n = 42) was the same, these retaining the rye genome, as demonstrated by GISH and FISH. These new synthesized allopolyploids constitute interesting models for investigating the evolutionary changes responsible for diploidization, and the chromosomal and genomic re-ordering that cannot be revealed in natural allopolyploids.     

Trypanosoma cruzi in Brazilian Amazonia: Lineages TCI and TCIIa in wild primates, Rhodnius spp. and in humans with Chagas disease associated with oral transmission

In this study, we provide phylogenetic and biogeographic evidence that the Trypanosoma cruzi lineages T. cruzi I (TCI) and T. cruzi IIa (TCIIa) circulate amongst non-human primates in Brazilian Amazonia, and are transmitted by Rhodnius species in overlapping arboreal transmission cycles, sporadically infecting humans. TCI presented higher prevalence rates, and no lineages other than TCI and TCIIa were found in this study in wild monkeys and Rhodnius from the Amazonian region. We characterised TCI and TCIIa from wild primates (16 TCI and five TCIIa), Rhodnius spp. (13 TCI and nine TCIIa), and humans with Chagas disease associated with oral transmission (14 TCI and five TCIIa) in Brazilian Amazonia. To our knowledge, TCIIa had not been associated with wild monkeys until now. Polymorphisms of ssrDNA, cytochrome b gene sequences and randomly amplified polymorphic DNA (RAPD) patterns clearly separated TCIIa from TCIIb-e and TCI lineages, and disclosed small intra-lineage polymorphisms amongst isolates from Amazonia. These data are important in understanding the complexity of the transmission cycles, genetic structure, and evolutionary history of T. cruzi populations circulating in Amazonia, and they contribute to both the unravelling of human infection routes and the pathological peculiarities of Chagas disease in this region.     

Crystal Structure of Diaminopimelate Epimerase from Arabidopsis thaliana, an Amino Acid Racemase Critical for l-Lysine Biosynthesis

Diaminopimelate (DAP) epimerase is a key enzyme for the biosynthesis of lysine in plants. Lysine is an essential dietary nutrient for mammals. In both plants and bacteria, DAP epimerase catalyzes the interconversion of ll-DAP and dl(meso)-DAP. The absence of a mammalian homolog makes DAP epimerase a promising target for the design of novel herbicides and antibacterials. This enzyme requires no cofactors and it functions through an unusual mechanism involving two cysteine residues acting in concert and alternating as a base (thiolate) and as an acid (thiol). The present study reports the crystal structures of two enzyme-inhibitor complexes of DAP epimerase from Arabidopsis thaliana with different isomers of the irreversible inhibitor and substrate mimic, 2-(4-amino-4-carboxybutyl)-aziridine-2-carboxylate, at 1.95 and 2.3 Å resolution. These structures provide the first atomic details of a plant amino acid racemase. Structural analysis reveals that ligand binding to a cleft between the two domains of the enzyme is accompanied by domain closure with two strictly conserved cysteine residues, Cys99 and Cys254, optimally positioned to perform acid/base catalysis via a carbanion stabilization mechanism on the stereogenic α-carbon atom of the amino acid. Stereochemical control in catalysis is achieved by means of a highly symmetric catalytic site that can accommodate both the l and d stereogenic centers of DAP at the proximal site, whereas specific interactions at the distal site require only the l configuration. Structural comparisons of the plant enzyme with its bacterial counterpart from Haemophilus influenzae reveal significant conservation of amino acid residues around the active site that extends to their three-dimensional structures and catalytic mechanism.     

Truncating loss-of-function mutations of <Emphasis Type="Italic">DISP1</Emphasis> contribute to holoprosencephaly-like microform features in humans

Defective function of the Sonic Hedgehog (SHH) signaling pathway is the most frequent alteration underlying holoprosencephaly (HPE) or its various clinical microforms. We performed an extensive mutational analysis of the entire human DISP1 gene, required for secretion of all hedgehog ligand(s) and which maps to the HPE 10 locus of human chromosome 1q41, as a HPE candidate gene. Here, we describe two independent families with truncating mutations in human DISP1 that resemble the cardinal craniofacial and neuro-developmental features of a recently described microdeletion syndrome that includes this gene; therefore, we suggest that DISP1 function contributes substantially to both of these signs in humans. While these clinical features are consistent with common HPE microforms, especially those linked to defective signaling by Sonic Hedgehog, we have insufficient evidence so far that functionally abnormal DISP1 alleles will commonly contribute to the more severe features of typical HPE.     

Enantioselective synthesis and antioxidant activity of 3‐(3,4‐dihydroxyphenyl)‐glyceric acid—Basic monomeric moiety of a biologically active polyether from Symphytum asperum and S. caucasicum

The racemic and enantioselective synthesis of a novel glyceric acid derivative, namely, 2,3‐dihydroxy‐3‐(3,4‐dihydroxyphenyl)‐propionic acid as well as the antioxidant activities is described. The virtually pure enantiomers, (+)‐(2R,3S)‐2,3‐dihydroxy‐3‐(3,4‐dihydroxyphenyl)‐propionic acid and (?)‐(2S,3R)‐2,3‐dihydroxy‐3‐(3,4‐dihydroxyphenyl)‐propionic acid were synthesized for the first time via Sharpless asymmetric dihydroxylation of trans‐caffeic acid derivatives using the enantiocomplementary catalysts, (DHQD)₂‐PHAL and (DHQ)₂‐PHAL. The determination of enantiomeric purity of the novel chiral glyceric acid derivatives was performed by high‐performance liquid chromatographic techniques on the stage of their alkylated precursors. The novel glyceric acid derivatives show strong antioxidant activity against hypochlorite and N,N‐diphenyl‐N‐picryl‐hydrazyl free radical. Their antioxidant activity is about 40‐fold higher than that of the corresponding natural polyether and three‐fold higher of trans‐caffeic acid itself. Chirality, 2010. © 2010 Wiley‐Liss, Inc.     

Morphological variation and relationships of Georgian populations of Vitis vinifera L. subsp. sylvestris (C.C. Gmel.) Hegi

Georgia is considered as one of the regions where for the first time wild growing grapevine plants were used and taken into cultivation by men. An ampelographic and ampelometric study of leaf characters and flower landmark morphometrics was carried out in seven populations of wild grapevine located in four river basins of three geographic regions – Western (1 popul.), Eastern (5 popul.) and Southern (1 popul.) Georgia, and then compared using principal component analysis and multivariate discriminant analysis allowing the populations to be distinguished. Lengths of main leaf veins and nectaries in male flowers were the variables, which allowed the best discrimination among populations. A mutation leading to white-fruited grapevine is found in one population. Pubescence varies within populations and even within an individual genome and could be used as a discriminant trait only in combination with shapes and sizes of leaves and other morphological characters. The results revealed significant differences among populations located in different geographic regions of the Southern Caucasus area, but the five investigated populations from Eastern Georgia differ only insignificantly. The high morphological variability of wild grapevine in Georgia might be considered as characterizing the large gene pool that contributed to the domestication process of grapevine.     

Chromosomal banding in three species of the genus Rineloricaria (Siluriformes, Loricariidae, Loricariinae)

Cytogenetic analyses were conducted in three species: Rineloricaria cadeae, Rineloricaria strigilata and Rineloricaria pentamaculata. The nucleolar organizing regions (NORs) were localized at the terminal position, on the ninth pair of the complement for R. cadeae and R. strigilata, on the eighth and sixth pair of st–a, respectively; and on the fifth pair of the complement for R. pentamaculata, the first pair of st–a. Rineloricaria strigilata and R. pentamaculata showed NOR heteromorphism and polymorphism, respectively. All species showed heterochromatin in the pericentromeric regions and associated with NORs, which were chromomycin A₃ (CMA₃) positive, demonstrating to be GC rich. The results show that NOR is nonconservative in this genus.     

Nature and duration of growth factor signaling through receptor tyrosine kinases regulates HSV-1 latency in neurons

Herpes simplex virus-1 (HSV-1) establishes life-long latency in peripheral neurons where productive replication is suppressed. While periodic reactivation results in virus production, the molecular basis of neuronal latency remains incompletely understood. Using a primary neuronal culture system of HSV-1 latency and reactivation, we show that continuous signaling through the phosphatidylinositol 3-kinase (PI3-K) pathway triggered by nerve growth factor (NGF)-binding to the TrkA receptor tyrosine kinase (RTK) is instrumental in maintaining latent HSV-1. The PI3-K p110α catalytic subunit, but not the β or δ isoforms, is specifically required to activate 3-phosphoinositide-dependent protein kinase-1 (PDK1) and sustain latency. Disrupting this pathway leads to virus reactivation. EGF and GDNF, two other growth factors capable of activating PI3-K and PDK1 but that differ from NGF in their ability to persistently activate Akt, do not fully support HSV-1 latency. Thus, the nature of RTK signaling is a critical host parameter that regulates the HSV-1 latent-lytic switch.     

Influence of chronological aging on the survival and nucleotide content of Saccharomyces cerevisiae cells grown in different conditions: occurrence of a high concentration of UDP-N-acetylglucosamine in stationary cells grown in 2% glucose

Saccharomyces cerevisiae cells (strain W303) grown in a minimal medium (containing 2% or 0.1% glucose) until exponential or stationary phase, were subjected to chronological aging in water, and yeast viability and nucleotide content were analyzed along several days of nutrient starvation. Cells collected in exponential phase (whether grown in the presence of 0.1% or 2% glucose) were viable up to five days and thereafter the viability decreased linearly with a half-survival rate of around eight days. ATP and other nucleoside triphosphates decreased similarly in both cases. Cells collected in stationary phase, and transferred to water, behaved differently whether grown in 0.1% or in 2% glucose, with a half-survival life of around nine and 28 days respectively. A double mutant in glycogen synthase (gsy1delta gsy2delta) and its isogenic wild-type strain, grown to stationary phase in 2% glucose, presented a similar half-survival life of around eight days. The W303 cells grown to stationary phase in the presence of 2% glucose showed a 7-fold increase of UDP-N-acetylglucosamine (UDP-GlcNAc) as compared with the level present in the cells grown in any of the other three metabolic situations. The nature of UDP-GlcNAc was established by MALDI-TOF ionization analysis. It is also worth noting that the rate of decay of NAD+ was lower than that of ATP in any of the situations here considered.