Photoregulation of some enzymes fromNeurospora crassa

Summary Light-grown cultures ofNeurospora crassa showed photoregulation of a number of enzymes. Proteases and cytosolic malate dehydrogenase showed an increase in activity. There was a decrease in the activity of mitochondrial malate dehydrogenase, isocitrate dehydrogenase and cytosolic glucose-6P-dehydrogenase, isocitrate dehydrogenase and isocitrate lyase.     

Genetic control and modifications of peroxidase pattern in two species ofNicotiana and their interspecific hybrid

Summary The peroxidase patterns ofNicotiana suaveolens, N. glutinosa and their interspecific hybrid have been studied, and their possible genetic control analyzed. Modifications of the isozymatic pattern along the plant have been observed.Acknowledgments. The authors thank Prof. J.R. Lacadena and Dr M. Pérez de la Vega for their valuable advice.     

The genetics of phytotoxin production by plant pathogenic fungi

Little is known about the genetic control of phytotoxin production by plant pathogenic fungi. The production of host-selective toxins known to play a role in disease development has been genetically analyzed in three species ofCochliobolus. InC. heterostrophus, a single genetic locus with two alleles has been identified controlling the production of HMT-toxin. This locus appears to be at or near the breakpoint of a chromosome rearrangement. Single genetic loci have also been identified controlling the production of HC-toxin byC. carbonum and HV-toxin byC. victoriae. The locus inC. carbonum may be a cluster of tightly linked genes.     

Gel-electrophoretic description of European populations ofTerellia virens (Loew) (Diptera,Tephritidae); implications for its use as an agent for the biological control ofCentaurea spp. (Asteraceae) in North America

Allozyme frequencies of 15 enzyme loci, 14 of which were polymorphic, were used to characterize sevenTerellia virens populations originating from three allopatrically distributedCentaurea species. The two populations whose origins were geographically furthest apart, from Israel (onC. iberica) and from Switzerland (onC. vallesiaca), showed relatively high values of genetic distance from the 5 populations sampled in Austria and Hungary (onC. maculosa) (Nei's D>0.07). The latter five displayed a high degree of genetic similarity. No diagnostic (fixed) allelic differences were observed between these three groups ofT. virens populations, but they could be well characterized by significant differences in allelic frequencies at 9 enzyme loci. Independently of this study, the populations from Switzerland (C. vallesiaca) and eastern Austria (C. maculosa) were selected as potential source populations for future introductions into North America for the biological control of introducedC. maculosa andC. diffusa. Based on the observed genetic differences and results from field experiments on the host specificity of these two potential source populations, it is argued that host specificity screening tests should be conducted separately for local (host plant) populations, as such populations might accept a different set of hosts. Biotype mismatch and the risk of spill-overs to native species could thus possibly be reduced.     

Communicating junctions between pillar cells in the gills of the atlantic hagfish,Myxine glutinosa

Summary In the respiratory lamellae of the gills of the atlantic hagfish,Myxine glutinosa, pillar cells are coupled by communicating junctions. It is suggested that these cells behave like a functional syncytium.Supported by the DFG, SFB 146. The authors are indebted to Drs F. Walvig and H. Stolte for kindly providing the hagfish. The expert technical assistance of G. Voss-Wermbter, Dipl.-Ing., and H. Heidrich is gratefully acknowledged.     

Intergeneric interactions betweenEimeria separata (Apicomplexa) andNippostrongylus brasiliensis (Nematoda) in the rat

Summary Ova production inNippostrongylus brasiliensis infected rats was significantly greater than in rats singly infected with the helminth whenEimeria separata infections were introduced 4, 6 and 11 days postinoculation withN. brasiliensis. Patent periods were unaltered during concurrent infections. These results suggest that the presence ofE. separata affects helminth fecundity but does not increaseN. brasiliensis longevity as has been shown withE. nieschulzi.This study was supported by NIH MB RS Grant RRO8012-8.     

Ethanol metabolizing system inDrosophila melanogaster: subcellular distribution of some main enzymes

Summary The subcellular distribution of some enzymes which play a part in ethanol metabolism have been determined by differential centrifugation of homogenates of adultD. melanogaster flies of various genotypes. Aldehyde dehydrogenase, recently discovered inD. melanogaster, is present in the five genotypes studied. It has been found however to be, in vitro at least, most active in a strain lacking both alcohol dehydrogenase and aldehyde oxidase.     

Detection of protease inhibitors in the hemolymph of resistantAnticarsia gemmatalis which are inhibitory to the entomopathogenic fungus,Nomuraea rileyi

Summary A complex of protease inhibitor activities has been detected in the hemolymph of the 6th instarAnticarsia gemmatalis larvae that are resistant to infection by the fungusNomuraea rileyi. A site-specific serine protease inhibitor extracted fromA. gemmatalis hemolymph inhibits both the germination ofN. rileyi conidia and subsequent germ tube development.     

Role of toxins in evolution and ecology of plant pathogenic fungi

Many fungal pathogens of plants adapt readily to changes in agriculture. Among the most revealing is a fungal group whose species produce host-selective toxins as key determinants of disease. Several lines of evidence support the hypothesis that these fungi evolved from opportunistic, low-grade pathogens by gaining new genetic information leading to toxin production; in some species, toxin production is known to be under single gene control. as a result of this evolution, these fungi became virulent and host-specialized. The best-known model cases belong to the generaCochliobolus andAlternaria; there are suggestions of evolutionary lines among these genera, with species that range from saprophytes to opportunists to specialized pathogens. Host specialization can lead to genetic isolation, a first step in speciation. Ability to produce host-selective toxin has allowed these fungi to exploit the monocultures and genetic uniformity of modern agriculture. Destructive epidemics have been the result.     

Genomic sources of regulatory variation in cis and in trans

Regulatory variation results from genetic changes with both cis and trans acting effects on gene expression. Here I describe the types of genetic variants that alter cis and trans regulation and discuss differences in the potential for cis and trans changes among different classes of genes. I argue that the molecular function of the protein encoded by each gene and how the gene is wired into the genomic regulatory network may influence its propensity for cis and trans regulatory changes.Received 15 February 2005; received after revision 12 April 2005; accepted 26 April 2005     

Recruitment communication and pheromone trails in the neotropical ants,Leptothorax (Nesomyrmex) spininodis andL. (N.) echinatinodis

Leptothorax (Nesomyrmex) spininodis andL. (N.) echinatinodis workers lay pheromone trails when returning from food sources to their nests. Workers from within the nest begin following the trail almost immediately upon the successful forager's return and do not require a leader. The trail remains effective for about four minutes under our laboratory conditions but it is unclear whether the trail alone is sufficient to induce recruitment or whether additional signals, perhaps emitted within the nest, are involved. Pheromone trails of this type have not previously been documented for leptothoracine ants.     

Enzymatic processing of pheromones and pheromone analogs

Summary Pheromone perception requires rapid enzymatic degradation of the active chemical signal in the sensory hairs. Three insects are used to illustrate chemical approaches to studying the degradation of pheromones by antennal enzymes. First, hydrolysis of acetate and haloacetate esters is examined in the diamondback moth,Plutella xylostella. Second, aldehyde oxidation and the selective inhibition of the oxidase and dehydrogenase activities are described for the tobacco budworm moth,Heliothis virescens. Finally, a stereochemical analysis of the epoxide-hydrase catalyzed addition of a water molecule to the oxirane ring of disparlure is described for the gypsy moth,Lymantria dispar.     

Drosophila melanogaster aldehyde dehydrogenase

Summary Subcellular fractionation by differential centrifugation confirms the presence of aldehyde dehydrogenase inD. melanogaster. It is found principally in the heavy mitochondrial fraction.     

Serological and genetical studies on the evolution of substrate specificity of flavone glycosyltransferase genes inSilene

Summary The variation in flavone glycosylation patterns inSilene is the result of the expression of six genetic loci, which control either the presence of allozymes differing in substrate specificity or isozymes regulated differently during development. Serological studies showed that at least three of these six loci are evolutionarily related. The genetic mechanisms leading to these complicated variation patterns and the role of this polymorphism for the plant in its interaction with the environment are discussed.     

Effect of the scorpion,Heterometrus fulvipes (C. Koch), venom on some enzyme systems in rat (albino) tissues

Summary Sublethal doses ofHeterometrus fulvipes venom decreased NADP-specific isocitrate dehydrogenase and malate dehydrogenase activity levels and increased NADP-specific glucose-6-phosphate dehydrogenase and alkaline phosphatase activity levels during a 48-h-period.Acknowledgments. D. V. thanks the Council of Scientific and Industrial Research, New Delhi, for awarding a Senior Research fellowship.     

Insect anti-juvenile hormone and juvenile hormone activity from plants in the genusNama

Summary The insect anti-juvenile hormones precocene I and II (7-methoxy-2,2-dimethyl-2H-1-benzopyran and 6,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran) were identified in three of nineNama (Hydrophyllaceae) species. Precocene I occurred inN. lobbii while precocene II occurred inN. hispidum, N. lobbii andN. sandwicense. N. hispidum contained the highest concentration (ca 0.5% dry weight) of precocene II, which was found in the leaves, stems, seed capsules, corolla, glandular trichomes, and seeds. In addition to the anti-juvenile hormone, insect juvenile hormone activity was detected in the organosoluble extracts ofN. rothrockii andN. sandwicense. N. sandwicense is the first plant discovered to contain compounds with both anti- and juvenile hormone activity.     

Acetaldehyde oxidation inDrosophila null-mutants for alcohol dehydrogenase

Summary Aldehyde dehydrogenase (ALDH) activity is demonstrated in four strains ofD. melanogaster lacking active alcohol dehydrogenase (ADH-null mutants). In the four strains, ALDH activities are similar to those found in a wild strain. It is concluded that ADH-null flies are able to detoxify acetaldehyde. This finding is discussed in relation with the dual function of ADH proposed recently.This work was supported by a grant from the Medical Research Council of Canada (MRC 6920) to Dr F. Garcin.     

A testis-specific lactate dehydrogenase in the pipid frog,Hymenochirus boettgeri

Summary Lactate dehydrogenase zymograms of mature testes ofHymenochirus boettgeri show in addition to the five isozymes composed of LDH-A and LDH-B subunits, a second 5-band system which is due to isozymes formed between LDH-A and a third subunit, LDH-C. These testis-specific LDH-C isozymes appear around 6 months after metamorphosis indicating that their expression is correlated with sexual maturity as is generally the case in mammals. This is the first report of a testis-specific LDH isozyme in a lower tetrapod; such isozymes have hitherto only been reported in mammals and in the pigeon.This study was supported by a grant from the Fond National Suisse de la Recherche Scientifique to H.R.K. We thank M. Sateur and F. Bourquin for their technical help.     

Transfer of secondary metabolites from the spongesDysidea fragilis andPleraplysilla spinifera to the mantle dermal formations (MDFs) of the mudibranchHypserlodoris webbi

The opisthobranch molluscHypselodoris webbi is able to select, among its potential preys, sponges chemically rich in furanosesquiterpenoids. The sequestered secondary metabolites act as defensive allomones against predators and are accumulated in some dorsal glands (MDFs). This transfer from sponges to MDFs has been proven by maintainingH. webbi together with some selected sponges in an aquarium for a prolonged period.     

What leads from <Emphasis Type="Italic">dead-end?</Emphasis>

The 129 mouse strain develops congenital testicular germ cell tumors (TGCTs) at a low frequency. TGCTs in mice resemble the testicular tumors (teratomas) that occur in human infants. The genes that cause these tumors in 129 have not been identified. The defect at the Ter locus increases TGCT incidence such that 94% of 129-Ter/Ter males develop TGCTs. The primary effect of the Ter mutation is progressive loss of primordial germ cells (PGCs) during embryonic development. This results in sterility in adult Ter/Ter mice on all mouse strain backgrounds. However, on the 129 background, Ter causes tumor development in addition to sterility. Therefore, Ter acts as a modifier of 129-derived TGCT susceptibility genes. Ter was identified to be a mutation that inactivates the Dead-end1 (Dnd1) gene. In this perspective, I discuss the possible areas of future investigations to elucidate the mechanism of TGCT development due to Dnd1 inactivation. Received 29 September 2006; received after revision 29 January 2007; accepted 19 February 2007