Loss of growth polarity and mislocalization of septa in a Neurospora mutant altered in the regulatory subunit of cAMP-dependent protein kinase.

In filamentous fungi, growth polarity (i.e. hyphal extension) and formation of septa require polarized deposition of new cell wall material. To explore this process, we analyzed a conditional Neurospora crassa mutant, mcb, which showed a complete loss of growth polarity when incubated at the restrictive temperature. Cloning and DNA sequence analysis of the mcb gene revealed that it encodes a regulatory subunit of cAMP-dependent protein kinase (PKA). Unexpectedly, the mcb mutant still formed septa when grown at the restrictive temperature, indicating that polarized deposition of wall material during septation is a process that is, at least in part, independent of polarized deposition during hyphal tip extension. However, septa formed in the mcb mutant growing at the restrictive temperature are mislocalized. Both polarized growth and septation are actin-dependent processes, and a concentration of actin patches is observed at growing hyphal tips and sites where septa are being formed. In the mcb mutant growing at the restrictive temperature, actin patches are uniformly distributed over the cell cortex; however, actin patches are still concentrated at sites of septation. Our results suggest that the PKA pathway regulates hyphal growth polarity, possibly through organizing actin patches at the cell cortex.     

Genetic analysis of agronomic traits in a cross between sugarcane (Saccharum officinarum L.) and its presumed progenitor (S. robustum Brandes & Jesw. ex Grassl)

Saccharum robustum Brandes & Jesw. ex Grassl has been suggested as the immediate progenitor species of cultivated sugarcane (S. officinarum L.) [4]. Chromosome pairing and assortment in these two species were previously studied by genetic analysis of single-dose DNA markers in parents in and 44 F₁ progeny of a cross between euploid, meiotically regular 2n=80S. officinarum LA Purple andS. robustum Mol 5829 [2]. This same population was subsequently clonally propagated and evaluated in replicated trials for quantitative traits important to sugarcane breeders. Numbers of stalks, tasseled stalks, and stalks with smut, and the average diameter of two stalks were determined one day prior to harvest. At harvest, plant material from each plot was weighed and evaluated for pol (sucrose content) and fiber percentages. Clones were significantly different (P<0.01) for all traits analyzed. Associations of 83 single-dose arbitrarily primed PCR genetic markers with quantitative trait loci (QTL) of recorded traits was determined by single-factor ANOVA, and multiple regression. QTL analysis revealed markers significantly (P<0.05) associated with the expression of each trait analyzed. Markers associated with QTL after multiple regression were tested for digenic linear × linear epistatic interactions. The various multilocus models explained between 23% and 58% of the total phenotypic variation and 32% and 76% of the genotypic variation for the various traits. Digenic interactions were uncommon. Implications for marker-assisted selection in sugarcane and sugarcane domestication are discussed.     

The effect of calcium chelators on microsomal pyridine nucleotide-linked dehydrogenases of sugarbeet cells

Cell suspension cultures of Beta vulgaris L., treated with calciumchelators or untreated, were used to characterize pyndine nucleotide-dependentdiaphorases of microsomes. The microsomal activity of NADH-dependentduroquinone reductase from cultures treated with 10 mM Na₂EGTAfor 24 h increased by a factor of 1.8 with respect to controlmicrosomes, and was mainly associated with particles of d=1.17gml^–1. NADPH-duroquinone reductase and NADH-ferricyanidereductase activities showed smaller increases. Bacterial protein-lipopolysaccharidecomplexes (prLPS) also promoted the increase of microsomal diaphorases;CaEGTA was Ineffective. EGTA effects on enzymes of supernatantand mitochondria were negligible, although Na₂EGTA treatmentinduced cell aggregation and strong acidification of the medium. When microsomes from control cultures were solubilized with1% LPC and fractionated in high-efficiency gel permeation columns(FPLC) the diaphorase activities were found associated to threemajor proteins: (i) NADH-specific quinone reductase (NADH-QR)of 340 kDa; (ii) pyndine nucleotide-nonspecific quinone reductase(NAD(P)H-QR) of 85 kDa also having ferricyanide reductase activity;(iii) NADH-specific ferricyanide reductase (NADH-FCR) of 38kDa. The microsomes from EGTA-treated cells also showed a highlyactive NADH-QR having a larger molecular mass (440 kDa) thanin control cells. NAD(P)H-QR also showed increased activity.We conclude that external Ca²⁺ chelation induces changes indehydrogenase components in microsomes. Furthermore, prLPS probablyexert part of their effect on plants through Ca²⁺ chelation. Key words: Beta vulgaris, cell cultures, calcium chelators, diaphorase, NAD(P)H-dehydrogenase, lipopolysaccharide, EGTA, quinone reductase     

Pigment interactions in chlorosomes of various green bacteria

Resonance Raman experiments were performed on different green bacteria. With blue excitation, i.e. under Soret resonance or preresonance conditions, resonance Raman contributions were essentially arising from the chlorosome pigments. By comparing these spectra and those of isolated chlorosomes, it is possible to evaluate how the latter retain their native structure during the isolation procedures. The structure of bacteriochlorophyll oligomers in chlorosomes was interspecifically compared, in bacteriochlorophyllc- and bacteriochlorophylle- synthesising bacteria. It appears that interactions assumed by the 9-keto carbonyl group are identical inChlorobium limicola, Chlorobium tepidum, andChlorobium phaeobacteroides. In the latter strain, the 3-formyl carbonyl group of bacteriochlorophylle is kept free from intermolecular interactions. By contrast, resonance Raman spectra unambiguously indicate that the structure of bacteriochlorophyll oligomers is slightly different in chlorosomes fromChloroflexus auranticus, either isolated or in the whole bacteria.     

Herbivory on calcicolous lichens: different food preferences and growth rates in two co-existing land snails

A total of 32 calcicolous lichen species, one alga and one bryophyte were recorded on a limestone wall in the grassland Great Alvar on the Baltic island of Öland, Sweden. Fourteen (41%) of these 34 species and free-living cyanobacteria showed herbivore damage, most probably due to grazing by the land snails Chondrina clienta and Balea perversa which inhabited the limestone wall. Three laboratory experiments were conducted to examine the food preferences of individuals of C. clienta and B. perversa collected at this site and to evaluate any association between their preference and the net food quality of the lichens to the snails. Chondrina clienta and B. perversa exhibited food preferences, which differed significantly between species. Within species, variation in food choice was similar among individuals. This indicates that snail populations may be composed of polyphagous individuals with similar food preferences. Different lichen species were of different net food quality to the snails as indicated by growth rate differences. In both snail species the most preferred lichen species of the choice experiment caused the largest weight increase in juveniles, viz. Caloplaca flavovirescens for C. clienta and Aspicilia calcarea for B. perversa. This suggest that the snail species studied differ in their abilities to deal with secondary compounds and physical characteristics of certain lichens or that they can utilize the energy and nutrients of these lichens to a different extent. It is suggested that differential food preferences might reduce the intensity of interspecific competition for resources (lichens) between C. clienta and B. perversa.     

Analysis of phytochrome- and ABA-deficient mutants suggests that ABA degradation is controlled by light in Nicotiana plumbaginifolia

The phytochrome chromophore-deficient mutant, pew1, of Nicotiana plumbaginifolia exhibited decreased germination and slower dehydration of detached leaves during water stress as compared with the wild-type. These physiological processes are controlled by abscisic acid (ABA) and we examined, therefore, whether phytochrome plays a specific role in the regulation of ABA metabolism using the pew1 mutant. The ABA contents of mature seeds and young leaves were analysed and in both cases mutant material was found to contain higher amounts of ABA as compared with the wild-type. This indicates that the phytochrome activation can lead to a decrease of the ABA level in the wild-type plant. The role of phytochromes was investigated in greater detail using the ABA-deficient mutant aba1 of N. plumbaginifolia exhibiting an early and synchronous germination. This mutant accumulates at very high levels a metabolite derived from a precursor (ABA-aldehyde) in the ABA biosynthetic pathway. The first biochemical characterization of this molecule, which corresponds to the glucose-conjugated ABA-alcohol (ABA-AG) is described. A pew1-aba1 double mutant exhibiting both an etiolated growth and early germination was also obtained. The comparable accumulation of ABA-AG in the pew1-aba1 double mutant as compared with the aba1 mutant allowed the proposition that, in a wild-type plant, the phytochrome-mediated light signal enhances ABA degradation rather than inhibits its biosynthesis.     

Y418C: a novel mutation in exon 9 of the glucocerebrosidase gene of a patient with Gaucher disease creates a new Bgl I site

We report a novel mutation in exon 9 of the glucocerebrosidase gene of a patient with Gaucher disease and of Sardinian origin.     

On the ecology of Colurellidae (Rotifera)

A material consisting of 45 colurellid rotifers from diverse waters in south and central Sweden was analyzed to reveal their relationships to their substrate. Periphytic substrates were generally preferred. Most species are obviously mobile and more or less euryecious, but a few show a predilection for bog environments. Some colurellids are euryhaline, but when inhabiting fresh water they prefer rivers and other environments with a high oxygen concentration, probably because of problems with osmoregulation.