Showing papers by "Alessandra Carattoli published in 1993"

Functional identification of al-3 from Neurospora crassa as the gene for geranylgeranyl pyrophosphate synthase by complementation with crt genes, in vitro characterization of the gene product and mutant analysis

Abstract: In this work the Neurospora crassa al-3 gene function was determined. Geranylgeranyl pyrophosphate (GGPP) synthase activity was measured in al-2 FGSC 313 and al-3 RP100 FGSC 2082 mutant strains by in vitro synthesis methods. This experiment showed that al-3 RP100 mutant expresses a reduced GGPP synthase activity. The mutated al-3 gene was cloned and sequenced; a single missense mutation was found changing serine into asparagine. Genetic complementation was performed by Escherichia coli transformation, with clusters of crt genes from Erwinia uredovora. Carotenoid accumulation was observed in E. coli transformants when the N. crassa al-3 gene substitutes the GGPP synthase gene (crtE) in the carotenogenic crt cluster. Cell-free studies with E. coli transformants gave direct evidence of the function of the al-3 protein as GGPP synthase and indicated that a short-chain prenylpyrophosphate, such as dimethylallyl pyrophosphate, is the genuine substrate.

Blue light regulated expression of geranylgeranyl pyrophosphate synthetase (Albino-3) gene in Neurospora crassa

Abstract: In the filamentous fungus Neurospora crassa several effects are induced by blue light during its life cycle. Carotenoid biosynthesis in mycelia (Harding, Shropshire 1980) and phase shifting and photosuppression of the circadian rhythm of conidiation (Feldman, 1982) are induced by blue light during vegetative growth. When sexual cycle takes place blue light stimulates the protoperitecia formation (Degli Innocenti, Russo 1983) and the positive phototropism of peritecial beaks (Harding, Melles, 1983). In N.crassa all these photoresponses are suppressed by mutations in two genes, called white collar (wc-1, wc-2) (Degli Innocenti, Russo, 1984). Blue light regulates a group of genes involved in the carotenogenesis (al-1, al-2 and al-3) (Schmidhauser et al., 1990; Lauter FR, Russo VEA unpublished data; Nelson et al., 1989), in the conidiation (con-5 and con-10) and other genes called bli, whose functions are not known yet (bli-3, bli-4, bli-7 and bli-13) (Sommer et al., 1989; Pandit NN, Russo VEA 1991). Blue light induction of carotenogenesis needs the transcriptional activation of the albino genes coding for the geranylgeranyl pyrophosphate synthetase (al-3), phytoene synthetase (al-2) and phytoene dehydrogenase (al-1). Three albino mutants which are defective in the structural genes necessary for carotenogenesis and described above, have been characterized in N.crassa. These mutants have white conidia and mycelia, unlike the orange conidia and mycelia characteristic of wild-type strains (Harding, Turner 1981).