Role of uronic acids present in phytopathogenic fungi as inducers of polygalacturonases during autolysis

The presence of uronic acids in the culture fluid and mycelium of the fungi: Alternaria alternata, Botrytis cinerea, Drechslera halodes, Fusarium culmorum, Fusarium oxysporum, Monilinia fructigena, Mucor mucedo, Rhizopus stolonifer and Trichoderma hamatum was detected and quantified. In these fungi the concentration of uronic acids increased during the growth phase and the maximal concentrations were found at the end of the growth phase or onset of autolysis both in the mycelium as well as in the culture fluid. The uronic acids were metabolized during the first days of autolysis decreasing to constant levels until the end of the autolytic period studied.The variations in the activity of polygalacturonase and polymethylgalacturonase present in the culture fluid were determined at the onset and during autolysis in these fungi. These enzymic activities were found in the culture fluid of these fungi, with exception of M. rouxii, and they showed an increasing activity in the first days of autolysis and later a slight increase or decrease was observed. The presence of uronic acids in these phytopathogenic or saprophytic fungi and the low levels detected during autolysis could be related to the induction of pectic enzymes and the pathogenicity of these fungi.     

Effect of calcium and other metal ions on pectic activities from autolysed cultures of Alternaria alternata

Abstract The effect of increasing concentrations of Ca²⁺, Mg²⁺, Cu²⁺, Zn²⁺, Na⁺ and EDTA on the pectic enzymic activities (polymethylgalacturonase, endopectinase and pectin-lyase) present in the autolytic complex from Alternaria alternata has been studied. In all cases the divalent metal ions and EDTA produced an increased inhibition correlated with increasing concentration of each ion. An opposite effect was shown by the Na⁺ ion, which produced an increase in pectic enzymic activities, principally at low concentrations.     

Chemical and physiological changes in fungi during autolysis

A comparative study was done on some of the chemical changes occurring during autolysis of cultures ofAspergillus flavus in both physiologically acid and alkaline media. The mycelium ofA. flavus lost during autolysis 44 % of its maximum dry weight in the physiologically alkaline medium, whereas this loss was apparently nil in the physiologically acid medium. Nitrogen containing compounds seemed not to be affected by autolysis either in the physiologically acid or alkaline media. The disappearance of P-containing compounds in mycelium ofA. flavus autolysed in both conditions (NO ₃ ^– and NH ₄ ⁺ as N source) amounted to 64 % in the alkaline autolysis and to nearly 77 % in the acid autolysis. The results we have obtained for the acid autolysis strongly suggest that very little activity is shown by autolytic enzymes in the interval 10–133 days of incubation, when measuring autolysis by the loss in mycelial dry weight.

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Zusammenfassung Eine vergleichende Untersuchung war unternommen an einigen der chemischen Veränderungen, die während der Autolyse der Kulturen vonAspergillus flavus in physiologischen sauren und alkalischen Medien vorkommen. Die Myzelien vonA. flavus haben während der Autolyse 44 % ihres größten Trockengewichtes in physiologisch alkalischem Medium verloren, während dieser Verlust in physiologisch saurem Medium anscheinend Null gewesen ist. Stickstoff enthaltende Substanzen erschienen während der Autolyse weder in physiologisch saueren noch in alkalischen Medien beeinflußt zu sein. Das Verschwinden von P-enthaltenden Substanzen in Myzelien vonA. flavus in Autolyse unter beiden Bedingungen (NO ₃ ^– und NH ₄ ⁺ als Stickstoffquelle) erreichte 64 % in alkalischer Autolyse und beinahe 77 % in der saueren Autolyse. Die Ergebnisse, die wir in der saueren Autolyse erhalten haben legen es sehr nahe, daß autolytische Enzyme eine sehr geringe Aktivität in der Zeitspanne von 10–133 Tagen der Inkubazion zeigen, wenn die Autolyse an dem Verlust des mycelialen Trockengewichtes gemessen wird.

     

Trinuclear iridium and rhodium complexes: the solution to a puzzle involving the multiple coordination possibilities of 1,8-naphthyridine-2-one ligands

The multiple coordination possibilities of 1,8-naphthyridine-2-one (HOnapy) and 5,7-dimethyl-1,8-napthyridine-2-one (HOMe₂napy) ligands allow the synthesis of a variety of tri- di- and mononuclear complexes, showing fluxional behaviour and frequent exchange of the coordinated ML₂ fragments. Thus, reactions of [M₂(μ-OMe)₂(cod)₂] (cod = 1,5-cyclooctadiene) with HOnapy and HOMe₂napy yield the compounds of the general formula [M(μ-OR₂napy) (cod)]_n (M = Ir, R = Me (1a, 1b, H (2); M = Rh, R = Me (3a, 3b). They crystallise as inconvertible yellow (a) and purple/orange (b) forms and also show a puzzling behaviour in solution. X-ray diffraction studies on both forms (3a, 3b) and spectroscopic data reveal that the yellow forms are mononuclear complexes whilst the dark-coloured crystals contain dinuclear complexes. In solution, the nuclearity of the complexes depends on the solvent. In addition both types of complexes are fluxional. The mixed-ligand complexes [M₂(μ-OMe₂napy)₂(CO)₂(cod)] M = Ir (5), Rh (6) have been isolated and characterised; they are found to be intermediates in the synthesis of the trinuclear complexes [M₃(μ₃-OMe₂napy)₂(CO)₂(cod)₂]⁺ M = Rh (8), Ir (9). Reactions of [IrCl(CO)₂(NH₂-p-tolyl] with the complexes [Rh(μ-OR₂napy)(diolefin)]_n followed by addition of a poor donor anion is a general one-pot synthesis for the hetertrinuclear complexes [Rh₂Ir(μ₃-OR₂napy)₂(CO)₂(diolefin)₂]⁺ (R=Me, DIOLEFIN = cod (10), tetrafluorobenzo-barrelene (tfbb) (11), 2,5-norbornadiene (nbd) (12); R=H, DIOLEFIN=cod (13)). This synthesis follows a stepwise mechanism from the mononuclear to the trinuclear complexes in which mixed-ligand heterodinuclear complexes are involved as intermediates of the type [(diolefin)Rh(μ-OMe₂napy)₂Ir(CO)₂]. Heteronuclear complexes which possess the core [RhIr₂]³⁺, such as [RhIr₂(μ₃-OR₂napy)₂(CO)₂(cod)₂]BF₄ (R=Me (14), H (15)), result from the reaction of 1 or 2 with [Rh(CO)₂S_x]⁺ (S = solvent). The trinuclear complexes undergo two chemically reversible one-electron oxidation processes. The chemical oxidation of 10, 14 and 9 with silver salts gives the mixed-valence trinuclear radicals [Rh₂Ir(μ₃-OMe₂napy)₂(CO)₂(cod)₂]²⁺ (16), [RhIr₂(μ₃-OMe₂napy)₂(CO)₂(cod)₂]²⁺ (17) and [Ir₃(μ₃-OMe₂napy)₂(CO)₂(cod)₂]²⁺ (18), which have been isolated as the perchlorate and tetrafluoroborate salts. The EPR spectrum of 16 indicates that the unpaired electron is essentially in an orbital delocalised on the metals. The molecular structures of the complexes 3a, 3b, 6, 10b and 16a are described. Crystals of 3a are triclinic, P-1, with a = 9.7393(2), b = 14.0148(4), c = 16.0607(4) Å, α = 88.122(3), β = 83.924(3), γ = 87.038(3)°, Z = 4; 3b crystallises in the Pna2_i orthorhhombic space group, with a = 16.7541(3), B = 11.7500(8), c = 17.7508(7) Å, Z = 4; complex 6 is packed in the monoclinic space group P2_i/c, a = 9.6371(1), b = 11.8054(4), c = 27.2010(9) Å, β = 90.556(4)°, Z = 4; crystals of 10b are monoclinic, P2₁/n, with a = 17.546(7), b = 13.232(6), c = 17.437(8) Å, β = 106.18(1)°, Z = 4; crystals of 16a are triclinic, P-1, with a = 10.318(4), b = 12.562(6), C = 19.308(8) Å, α = 92.12(8), β = 97.65(9), γ = 90.68(5)°, Z = 2. The five different structures show the coordination versatility of the OMe₂napy molecule as ligand, which behaves as a N,N′-chelating (3a), bidentate N,O-donor (3b, 6), or as a tridentate N,N′,O-donor bridging ligand (10b, 16a).     

Phylogeny of Greya (Lepidoptera: Prodoxidae), based on nucleotide sequence variation in mitochondrial cytochrome oxidase I and II: congruence with morphological data

The phylogeny of Greya Busck (Lepidoptera: Prodoxidae) was inferred from nucleotide sequence variation across a 765-bp region in the cytochrome oxidase I and II genes of the mitochondrial genome. Most parsimonious relationships of 25 haplotypes from 16 Greya species and two outgroup genera (Tetragma and Prodoxus) showed substantial congruence with the species relationships indicated by morphological variation. Differences between mitochondrial and morphological trees were found primarily in the positions of two species, G. variabilis and G. pectinifera, and in the branching order of the three major species groups in the genus. Conflicts between the data sets were examined by comparing levels of homoplasy in characters supporting alternative hypotheses. The phylogeny of Greya species suggests that host-plant association at the family level and larval feeding mode are conservative characters. Transition/transversion ratios estimated by reconstruction of nucleotide substitutions on the phylogeny had a range of 2.0-9.3, when different subsets of the phylogeny were used. The decline of this ratio with the increase in maximum sequence divergence among taxa indicates that transitions are masked by transversions along deeper internodes or long branches of the phylogeny. Among transitions, substitutions of A-->G and T-->C outnumbered their reciprocal substitutions by 2-6 times, presumably because of the approximately 4:1 (77%) A+T-bias in nucleotide base composition. Of all transversions, 73%-80% were A<-->T substitutions, 85% of which occurred at third positions of codons; these estimates did not decrease with an increase in maximum sequence divergence of taxa included in the analysis. The high frequency of A<-->T substitutions is either a reflection or an explanation of the 92% A+T bias at third codon positions.      

Protoplast production from filamentous fungi with their own autolytic enzymes

Abstract Production of protoplasts in different genera of filamentous fungi with their own lytic enzymes obtained from autolyzed cultures, as well as the regeneration of these protoplasts, has been studied. The results support the idea that the use of these autolytic enzymes could be a general method of production of protoplasts from filamentous fungi.