Enrique Cerdá-olmedo - Academia.edu (original) (raw)

Papers by Enrique Cerdá-olmedo

Genetics, Jun 1, 2001

Sexual interaction between strains of opposite sex in many fungi of the order Mucorales modifies ... more Sexual interaction between strains of opposite sex in many fungi of the order Mucorales modifies hyphal morphology and increases the carotene content. The progeny of crosses of Phycomyces blakesleeanus usually include a small proportion of anomalous segregants that show these signs of sexual stimulation without a partner. We have analyzed the genetic constitution of such segregants from crosses that involved a carF mutation for overaccumulation of ␤-carotene and other markers. The new strains were diploids or partial diploids heterozygous for the sex markers. Diploidy was unknown in this fungus and in the Zygomycetes. Random chromosome losses during the vegetative growth of the diploid led to heterokaryosis in the coenocytic mycelia and eventually to sectors of various tints and mating behavior. The changes in the nuclear composition of the mycelia could be followed by selecting for individual nuclei. The results impose a reinterpretation of the sexual cycle of Phycomyces. Some of the intersexual strains that carried the carF mutation contained 25 mg ␤-carotene per gram of dry mass and were sufficiently stable for practical use in carotene production.

Mutation Research: Fundamental And Molecular Mechanisms Of Mutagenesis, May 1, 1967

Proceedings of the National Academy of Sciences of the United States of America, Jun 1, 1991

In vivo channeling of substrates in an enzyme aggregate for ,8-carotene biosynthesis [Phycomyces/... more In vivo channeling of substrates in an enzyme aggregate for ,8-carotene biosynthesis [Phycomyces/nicotine/idaz le/a-pcollne/2-(4-lorophenyl)thlotiethylmln]

Springer eBooks, 1996

Blue light is used as a source of information on the environment by all kind of living beings, fr... more Blue light is used as a source of information on the environment by all kind of living beings, from microbes to animals. The Zygomycete fungus Phycomyces blakesleeanus is notorious for the variety of responses to blue light, various invisible radiations, and other stimuli. The copious literature on the behaviour of Phycomyces accumulated over more than a century was critically examined in Bergman et al. (1969) and Cerda-Olmedo and Lipson (1987). Galland (1990) updated and compared knowledge on Phycomyces and plant phototropism. We will discuss here only the aspects that have progressed in the last five years.

Molecular Genetics And Genomics, Aug 1, 1987

Exposure to heat, acetate, or propionate activates the spores of the fungus Phycomyces blakesleea... more Exposure to heat, acetate, or propionate activates the spores of the fungus Phycomyces blakesleeanus and allows them to germinate. Using counterselection with the antibiotic N-glycosyl-polyfungin, seven mutants were isolated on the basis of decreased spore activation by propionate. The nine mutants showed decreased activation by both chemicals and by heat, increased heat lethality, and altered patterns of trehalase activation. These and other observations indicate that spore activation by the three agents and spore death by heat are mediated by the same cellular component(s), which is probably involved in the regulation of cyclic AMP concentration.

Planta, Aug 1, 1995

The giant sporangiophores of Phycomyces blakesleeanus turn towards blue and away from ultraviolet... more The giant sporangiophores of Phycomyces blakesleeanus turn towards blue and away from ultraviolet C sources (wavelength under 310 nm). We have isolated fifteen mutants with normal blue tropism but defective ultraviolet tropism. Wild-type sporangiophores described a double turn when exposed successively to blue and ultraviolet beams coming from the same side; under certain conditions, the mutants turned only to the blue. The new uvi mutations modified the behaviour in heterokaryosis and were lethal in homokaryosis, i.e., they affected essential cellular components. The responses of the wild type and one of the mutants were registered and evaluated with a computer-aided device. The mutant behaved normally under blue light, but took longer than the wild type to turn away from the ultraviolet source. With very weak ultraviolet stimuli (10(-8) and l0(-9) W m-2), the wild type turned towards the source, but the mutant did not respond. Calculations of absorbed-energy distributions in the sporangiophore showed that Phycomyces responds differently to similar spatial distributions of blue and ultraviolet radiations. Wild-type and mutant sporangiophores had the same high ultraviolet absorption due to gallic acid. We conclude that ultraviolet tropism is not just a modification of blue phototropism due to the high ultraviolet absorption of the sporangiophores. Phycomyces has a separate sensory system responsive to ultraviolet radiation, but not to blue light.

Journal of Natural Products, Jan 5, 2001

Mutation Research: Fundamental And Molecular Mechanisms Of Mutagenesis, Jun 1, 1975

N-Methyl-N'-nitro-N-nitrosoguanidine (nitrosoguanidine) causes an unexpectedly high frequency of ... more N-Methyl-N'-nitro-N-nitrosoguanidine (nitrosoguanidine) causes an unexpectedly high frequency of closely linked double mutants because of its specificity for chromosome regions in replication. Low nitrosoguanidine concentrations (I/zg/ml) in liquid cultures allow replication at the normal rate and are mutagenic. It was expected that mutations would be spread over the chromosome as it replicated, but a high frequency of closely linked double mutants was found. If a thymine auxotroph is grown in the presence of 5-bromodeoxyuridine (BUdR) and nitrosoguanidine, then exposed to 313-nm radiation (which destroys BUdR-substituted DNA), the mutation frequency is much higher among survivors than among non-irradiated cells. It is concluded that nitrosoguanidine inhibits DNA replication in a small fraction of the population and that mutations are induced in that same fraction. Nitrosoguanidine treatment leads to a high frequency of closely linked double mutants under all known conditions.

Applied and Environmental Microbiology, May 1, 1983

Molecular Genetics And Genomics, 1976

Three independent mutations of Phycomyces blakesleeanus resulting in overaccumulation of beta-car... more Three independent mutations of Phycomyces blakesleeanus resulting in overaccumulation of beta-carotene are recessive and belong to the same complementation group. The corresponding gene has been named carS. Evidence is presented that gene carS is not the same as gene carA, previously defined by mutations blocking carotene production. Vitamin A increases carotenogenesis in wild types and in carS mutants to about the same extent. Intersexual heterokaryosis increases carotenogenesis most prominently in carS genetic backgrounds (up to 300 times the production of the wild type in the same conditions). Vitamin A, intersexual heterokaryosis and carS mutations are thought to stimulate carotenogenesis through different mechanisms. It is suggested that the carS gene product participates in end-product regulation of the pathway.

Photochemistry and Photobiology, Sep 1, 1996

Ultraviolet B radiation (wavelength 290-310 nm) does not induce any specific lethal effects in th... more Ultraviolet B radiation (wavelength 290-310 nm) does not induce any specific lethal effects in the fungus Phycomyces blakesleeanus, according to a heterokaryon test that responds to the nature of the lethal damage. This agent is about 10 times less lethal than UVC radiation from germicidal lamps (254 nm), but it kills cells through the same photoreactivable lesions, due to the UV absorption of DNA. Carotenes do not protect Phycomyces against UV damage, either B or C, lethal or not. This was shown by Darwinian competition experiments between strains containing very different carotene concentrations and between strains containing similar concentrations of different carotenes (phytoene, lycopene, p-carotene). A shading effect of carotenes against UV radiation is likely, but it was insignificant under the conditions of the experiments.

Mutation Research: Fundamental And Molecular Mechanisms Of Mutagenesis, Jul 1, 1975

Current Genetics, May 1, 1982

Genetic analysis of carotenogenesis in Phycomyces is hampered by the inability of most mutants to... more Genetic analysis of carotenogenesis in Phycomyces is hampered by the inability of most mutants to complete the sexual cycle. Heterokaryons between complementing mutants or between a mutant and a helper strain are, however, fertile. Using this method crosses have been carried out between mutants representing the different known genes and phenotypes.The gene for phytoene dehydrogenase, carB, is closely linked to carRA, a bifunctional gene specifying both lycopene cyclase and a product involved in substrate transfer. The regulatory gene carS lies on the same chromosome, but not close to the structural genes. The situation is thus reminiscent of an operon.Two chemoinsensitive mutants, showing little or no response to the effects of retinol and 2-(4-chlorophenyl)thiotriethylamine HCl on carotenogenesis, carry mutations in separate genes. One of these is probably identical with carRA; the other is a new gene termed carl.

Molecular Genetics and Genomics, 2002

Terpenoids or isoprenoids constitute a vast family of organic compounds that includes sterols and... more Terpenoids or isoprenoids constitute a vast family of organic compounds that includes sterols and carotenoids. The terpenoids in many organisms share early steps in their biosynthesis, including the synthesis of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) and its conversion to mevalonate. We have cloned and characterised the genes hmgS for HMG-CoA synthase and hmgR for HMG-CoA reductase from the Zygomycete Phycomyces blakesleeanus. Single copies of these genes are present in the Phycomyces genome. The predicted product of hmgS is largely hydrophilic and that of hmgR has eight putative transmembrane segments and a large hydrophilic domain. The hydrophilic domain suces for catalytic activity, as shown by expressing it in Escherichia coli. Several features in the promoter of hmgS and in HMG-CoA reductase resemble motifs known to be involved in sterol-mediated regulation and sterol sensing. Carotene-overproducing mutants contain more hmgS mRNA than the wild type, possibly in response to an increased demand for HMG-CoA.

Plant Science Letters, 1974

Strains of Phycomyces blakesleeanus carrying mutations in gene carB accumulate large amounts of p... more Strains of Phycomyces blakesleeanus carrying mutations in gene carB accumulate large amounts of phytoene. A leaky carB mutant, isolated from a red, lycopene-producing strain, accumulates decreasing amounts of phytoene, phytofluene, ~-carotene, neurosporene, and lycopene. This indicates that the product of gene carl} carries out the four successive dehydrogenations needed to convert phytoene to lycopene.

Genetics Research, Dec 1, 1980

The mutations which block lycopene cyclization and those which stop substrate transfer along the ... more The mutations which block lycopene cyclization and those which stop substrate transfer along the carotene pathway are very closely linked in Phycomyces. Simultaneous blocking of both processes commonly results from single exposures to mutagens; and both blockings may be simultaneously removed after a second exposure. The frequencies of different kinds of mutants after treatments with the mutagens iy-methyl-iV'-nitro-iV-nitrosoguanidiiie and ICR-170, their reversion patterns, and recombination analyses indicate that lycopene cyclization and substrate transfer are governed by separate segments of a single bifunctional gene.

Molecular Genetics And Genomics, Sep 1, 1968

The comparative study of these strains shows that diazomethane, a decomposition product of nitros... more The comparative study of these strains shows that diazomethane, a decomposition product of nitrosoguanidine, is the principal agent involved in both lethal and mutagenic effects of nitrosoguanidine above pH 5. Nitrosoguanidine is the lethal agent at pH 5 and it is possibly a lesser mutagen itself. 2. There are two types of chromosomal effects, lethal (susceptible to repair replication) and mutagenie (non-repairable), both due mostly to diazomethane. 3. The expression of mutations was found to be independent of DNA replication or repair. The optimal conditions for nitrosoguanidine mutagenesis are discussed.

Journal of Molecular Biology, May 1, 1968