The COMPASS family of H3K4 methylases in Drosophila

Methylation of histone H3 lysine 4 (H3K4) in Saccharomyces cerevisiae is implemented by Set1/COMPASS, which was originally purified based on the similarity of yeast Set1 to human MLL1 and Drosophila melanogaster Trithorax (Trx). While humans have six COMPASS family members, Drosophila possesses a representative of the three subclasses within COMPASS-like complexes: dSet1 (human SET1A/SET1B), Trx (human MLL1/2), and Trr (human MLL3/4). Here, we report the biochemical purification and molecular characterization of the Drosophila COMPASS family. We observed a one-to-one similarity in subunit composition with their mammalian counterparts, with the exception of LPT (lost plant homeodomains [PHDs] of Trr), which copurifies with the Trr complex. LPT is a previously uncharacterized protein that is homologous to the multiple PHD fingers found in the N-terminal regions of mammalian MLL3/4 but not Drosophila Trr, indicating that Trr and LPT constitute a split gene of an MLL3/4 ancestor. Our study demonstrates that all three complexes in Drosophila are H3K4 methyltransferases; however, dSet1/COMPASS is the major monoubiquitination-dependent H3K4 di- and trimethylase in Drosophila. Taken together, this study provides a springboard for the functional dissection of the COMPASS family members and their role in the regulation of histone H3K4 methylation throughout development in Drosophila.     

A hypomorphic mutation in Lpin1 induces progressively improving neuropathy and lipodystrophy in the rat

The Lpin1 gene encodes the phosphatidate phosphatase (PAP1) enzyme Lipin 1, which plays a critical role in lipid metabolism. In this study we describe the identification and characterization of a rat model with a mutated Lpin1 gene (Lpin1(1Hubr)), generated by N-ethyl-N-nitrosourea mutagenesis. Lpin1(1Hubr) rats are characterized by hindlimb paralysis and mild lipodystrophy that are detectable from the second postnatal week. Sequencing of Lpin1 identified a point mutation in the 5'-end splice site of intron 18 resulting in mis-splicing, a reading frameshift, and a premature stop codon. As this mutation does not induce nonsense-mediated decay, it allows the production of a truncated Lipin 1 protein lacking PAP1 activity. Lpin1(1Hubr) rats developed hypomyelination and mild lipodystrophy rather than the pronounced demyelination and adipocyte defects characteristic of Lpin1(fld/fld) mice, which carry a null allele for Lpin1. Furthermore, biochemical, histological, and molecular analyses revealed that these lesions improve in older Lpin1(1Hubr) rats as compared with young Lpin1(1Hubr) rats and Lpin1(fld/fld) mice. We observed activation of compensatory biochemical pathways substituting for missing PAP1 activity that, in combination with a possible non-enzymatic Lipin 1 function residing outside of its PAP1 domain, may contribute to the less severe phenotypes observed in Lpin1(1Hubr) rats as compared with Lpin1(fld/fld) mice. Although we are cautious in making a direct parallel between the presented rodent model and human disease, our data may provide new insight into the pathogenicity of recently identified human LPIN1 mutations.     

Morpho-agronomic and molecular characterisation of oil palm Elaeis guineensis Jacq. material from Angola

The characterisation of phytogenetic resources is used to improve conservation strategies, promote new sources of plant material, and design breeding strategies. In this study, we evaluated oil palm material with nine morpho-agronomic traits and 30 microsatellite markers (Simple Sequence Repeats; SSRs) that had been previously collected in five geographical regions of Angola. The analysis of variance for components of bunch production and oil yield showed highly significant (p?<?0.001) statistical differences between geographical regions and among families for all traits evaluated. The SSRs were highly informative, suggesting high genetic diversity (H _T ?=?0.666) among the accessions evaluated. However, the clustering pattern at both morpho-agronomic and molecular levels did not match the geographical distribution of accessions, showing a low genetic differentiation (G _ST ?=?0.039) between regions. On the other hand, genotypic (G _ST ?=?0.150) and phenotypic differences were found among families, which could offer the potential for future genetic gains in the oil palm. The information generated indicates that the evaluated accessions have desirable characteristics that should be included in breeding programs, which could expand the genetic basis of the crop.     

Toxic and nontoxic microcystis colonies in natural populations can be differentiated on the basis of rRNA gene internal transcribed spacer diversity

Assessing and predicting bloom dynamics and toxin production by Microcystis requires analysis of toxic and nontoxic Microcystis genotypes in natural communities. We show that genetic differentiation of Microcystis colonies based on rRNA internal transcribed spacer (ITS) sequences provides an adequate basis for recognition of microcystin producers. Consequently, ecological studies of toxic and nontoxic cyanobacteria are now possible through studies of rRNA ITS genotypic diversity in isolated cultures or colonies and in natural communities. A total of 107 Microcystis colonies were isolated from 15 lakes in Europe and Morocco, the presence of microcystins in each colony was examined by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and they were grouped by rRNA ITS denaturing gradient gel electrophoresis (DGGE) typing. Based on DGGE analysis of amplified ITSa and ITSc fragments, yielding supplementary resolution (I. Janse et al., Appl. Environ. Microbiol. 69:6634-6643, 2003), the colonies could be differentiated into 59 classes. Microcystin-producing and non-microcystin-producing colonies ended up in different classes. Sequences from the rRNA ITS of representative strains were congruent with the classification based on DGGE and confirmed the recognition of microcystin producers on the basis of rRNA ITS. The rRNA ITS sequences also confirmed inconsistencies reported for Microcystis identification based on morphology. There was no indication for geographical restriction of strains, since identical sequences originated from geographically distant lakes. About 28% of the analyzed colonies gave rise to multiple bands in DGGE profiles, indicating either aggregation of different colonies, or the occurrence of sequence differences between multiple operons. Cyanobacterial community profiles from two Dutch lakes from which colonies had been isolated showed different relative abundances of genotypes between bloom stages and between the water column and surface scum. Although not all bands in the community profiles could be matched with isolated colonies, the profiles suggest a dominance of nontoxic colonies, mainly later in the season and in scums.     

Polyhydroxybutyrate: An intriguing biopolymer

The microbial polymer poly-3-hydroxybutyrate (PHB) and related poly-hydroxyalkanoates, such as poly-3-hydroxyvalerate and poly-3-hydroxyoctanoate, are unique biodegradable thermoplastics of considerable commercial importance. The structure, properties and regulation of synthesis and degradation of PHB are reviewed and the microbial production of copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate, with properties varying according to copolymer composition, is discussed.     

Chiroptical and stoichiometric evidence of a specific,primary dimerisation process in alginate gelation

The stoichiometry of calcium-ion chelation to alginate chains has been investigated by circular dichroism (c.d.), and by equilibrium dialysis in the presence of various concentrations of sodium chloride. C.d. intensity in the carboxylate π → π * spectral region increases linearly with calcium-ion concentration up to a level equivalent to half the total poly-L-guluronate stoichiometric requirement, and thereafter shows little further change. Similarly, the level of bound calcium resistant to displacement by swamping concentrations of sodium ions is equivalent to half the stoichiometric requirement of poly-L-guluronate chain-sequences alone. In terms of the previously developed “egg-box” model of co-operative junction-zone formation in alginate gelation, these results are interpreted as showing that the primary mechanism of interchain association is by dimerisation of poly-L-guluronate chain-segments in a regular, buckled, two-fold conformation related to that characterized for the free acid in the solid state, with tight interchain chelation of calcium to the carboxylate groups on the interior faces of the dimer (i.e., half the carboxylate residues of the participating chain-sequences). This interpretation is entirely consistent with previous evidence from electron microscopy, and offers a simple rationalisation of experimental results from competitive-ion binding studies.     

Serological Comparison of the Three Morphological Phases of Coccidioides immitis by the Agar Gel Diffusion Method

Hyperimmune sera against spherules and against arthrospores of Coccidioides immitis were prepared by inoculation of rabbits. The antibody content of these sera was studied by the agar gel diffusion method. It was observed that antispherule pooled sera formed multiple precipitin bands with extracts of spherules and of arthrospores. The antiarthrospore pooled serum, however, failed to precipitate with the spherule extract, and formed a single band in the presence of an arthrospore solution. When the spherule and the arthrospore extracts were tested with a variety of different antisera, it was observed that the spherule preparation formed bands only in combination with anti-purified spherule pooled serum, whereas the arthrospore extract precipitated with anti-purified spherule, antiarthrospore, and anti-Histoplasma capsulatum pooled sera. It was also observed that a spherule culture supernatant solution formed five precipitin bands in combination with anti-spherule pooled sera, formed one band with pooled antiserum from rabbits with coccidioidomycosis, and did not precipitate in the presence of antiarthrospore pooled serum. Coccidioidin, however, formed two bands in the presence of any of these antisera. It was therefore concluded that extracts from the spherule phase of C. immitis differed from solutions obtained from the arthrospore and mycelial phases.     

Calorimetric and chiroptical evidence of aggregate-driven helix formation in carrageenan systems

Thermally induced, order-disorder transitions of iota- and kappa-carrageenan have been monitored by optical rotation and differential-scanning calorimetry in various ionic environments. Conformational ordering in kappa-carrageenan is observed only in the presence of cations that have been shown previously to promote helix-helix aggregation, and shows marked hysteresis between heating and cooling. Iota-carrageenan, by contrast, shows an order-disorder transition in the non-aggregating, tetramethylammonium salt form, at substantially lower temperature than for kappa-carrageenan, and without hysteresis. In the presence of potassium ions, which are known to promote aggregation, iota-carrageenan shows two distinct thermal-transitions, one without hysteresis at the same temperature as observed under non-aggregating conditions, and one with significant hysteresis close to the temperature of the kappa-carrageenan transition. We interpret these transitions as helix-to-coil and aggregated helix-to-coil, respectively. This interpretation is supported by measurements of the enthalpy changes of the transitions; ΔH values show a systematic increase with increasing aggregation and hysteresis. We conclude that the double helix of iota-carrageenan can exist as a stable entity in isolation, but may be further stabilised by aggregation, whereas the kappa-carrageenan helix is stable only when aggregated.