RESUMO
We present a comprehensive phylogeny derived from 5 genes, nucSSU, nucLSU rDNA, TEF1, RPB1 and RPB2, for 356 isolates and 41 families (six newly described in this volume) in Dothideomycetes. All currently accepted orders in the class are represented for the first time in addition to numerous previously unplaced lineages. Subclass Pleosporomycetidae is expanded to include the aquatic order Jahnulales. An ancestral reconstruction of basic nutritional modes supports numerous transitions from saprobic life histories to plant associated and lichenised modes and a transition from terrestrial to aquatic habitats are confirmed. Finally, a genomic comparison of 6 dothideomycete genomes with other fungi finds a high level of unique protein associated with the class, supporting its delineation as a separate taxon.
RESUMO
A procedure has been established for Agrobacterium tumefaciens-mediated genetic transformation of Hevea brasiliensis embryogenic friable calli. Precultivation of tissues on a CaCl(2)-free maintenance medium dramatically enhanced the transient activity of the reporter gene, gusA encoding beta-glucuronidase (GUS). The increase was first noticed in highly active cells (undifferentiated or/and embryogenic), in tissues precultured for 2-8 weeks. Beyond 8 weeks of preculture, GUS activity increased again, but this time in tissues consisting of differentiated cells accumulating polyphenols. Out of five Agrobacterium strains cocultivated with CaCl(2)-free precultured tissues, only inoculation with EHA105pC2301 led to high transient GUS activity. Paromomycin proved more effective than kanamycin for the selection of transformed cells, as it inhibits the growth of non-transformed cells more radically. Five paromomycin-resistant callus lines were established. The presence of gusA and neomycin phosphotransferase ( nptII) genes in the plant genome was confirmed by DNA amplification, and by Southern hybridization. These results confirmed that A. tumefaciens is an effective system for mediating stable transformation of rubber tree calli with a low copy number of transgenes. Transgenic callus lines constitute a useful tool for studying genes of interest on a cellular level and for regenerating transgenic rubber trees.
Assuntos
Agrobacterium tumefaciens/genética , Agrobacterium tumefaciens/fisiologia , Cloreto de Cálcio/farmacologia , Técnicas de Cultura/métodos , Hevea/embriologia , Hevea/genética , Meios de Cultura/química , Hevea/efeitos dos fármacos , Canamicina/farmacologia , Paromomicina/farmacologia , Plantas Geneticamente Modificadas , Transformação GenéticaRESUMO
Ethylene, used as a stimulant of latex production in Hevea brasiliensis, significantly activates the regenerating metabolism within the laticiferous cells. In this context, attention was focused on glutamine synthetase (GS; EC 6.3.1.2), a key enzyme in nitrogen metabolism. A specific and significant activation of the cytosolic glutamine synthetase (GScyt) in the laticiferous cells after ethylene treatment parallels the increase of latex yield. A marked accumulation of the corresponding mRNA was found, but in contrast, a slight and variable increase of the polypeptide level is at the limit of detection by western blotting. The GS response to ethylene might be mediated by ammonia that increases in latex cytosol following ethylene treatment. The physiological significance for such a regulation by ethylene of the GScyt is discussed in terms of the nitrogen requirement for protein synthesis associated with latex regeneration.
