Identification de varietes de soja par electrophorese des proteines

Diplôme : BT

Identification de varietes de soja par electrophorese des proteines

Diplôme : BT

PCR detection of the two "Candidatus" liberobacter species associated with greening disease of citrus

International audienc

PCR detection of the two "Candidatus" liberobacter species associated with greening disease of citrus

International audienc

The phloemlimited bacterium of greening disease of citrus is a member of the a subdivision of the Proteobacteria

Using the PCR, we amplified the 16s ribosomal DNAs (rDNAs) of an Asian strain and an African strain of the uncultured, gram-negative, walled, phloem-limited bacterium-like organism (BLO) associated with citrus greening disease. We evaded coamplification of chloroplast 16s rDNA by using restriction enzymes; the chloroplast 16s rDNA was sensitive to BclI digestion and resistant to EcoRI digestion, while the 16s rDNA of the BLO was resistant to BclI digestion and sensitive to EcoRI digestion. The 16s rDNA of the African BLO strain was amplified from BclI-digested DNA extracted from infected periwinkle leaf midribs. The Asian strain was isolated from plant extract by using a specific monoclonal antibody coated onto the surface of a PCR tube. The 16s rDNAs of the two BLO strains were cloned and sequenced. Comparisons with sequences of 16s rDNAs obtained from the GenBank data base revealed that the two citrus greening disease BLOs belong to the alpha subdivision of the class Proteobucteriu. Even though their closest relatives are members of the alpha-2 subgroup, these BLOs are distinct from this subgroup as we observed only 87.5 % homology between the 16s rDNAs examined. Therefore, the two BLOs which we studied probably are members of a new lineage in the a subdivision of the Proteobucteriu. We propose the trivial name “Iiberobacter ” for this new group of bacteria and will wait until additional characteristics have been determined before we propose a formal name. The procaryote associated with citrus greening disease wa

Comparison of the 16S/23S Ribosomal Intergenic Regions of “Candidatus Liberobacter asiaticum” and “Candidatus Liberobacter africanum”, the two species associated with Citrus Huanglongbing (Greening) Disease

16S/23S intergenic spacer regions from the rRNA operons of two strains of “Candidatus Liberobacter asiaticum ” and one strain of “Candidatus Liberobacter africanum ” were cloned and sequenced. The intergenic spacers of the two “Candidatus L. asiaticum ” strains studied are identical and contain the genes for isoleucine tRNA (tRNA”‘) and alanine tRNA (tRNAMa) separated by 11 nucleotides. The intergenic spacer of the “Candidatus L. africanum ” strain contains only one tRNA gene (tRNANa). The level of homology between the intergenic spacers of the two liberobacter species is 79.46%. Ribosomal operons with 16S/23S spacer regions other than those studied might be present in the two “Candidatus Liberobacter ” species. Huanglongbing (HLB) (greening) disease is one of the most severe diseases of citrus, occurring in Asian and African countries, in the Arabic Peninsula, and on Madagascar, Reunion, and Mauritius, which are islands in the Indian Ocean (2, 5). The agent of the disease is a bacterium which is restricted to the phloem sieve tubes of infected plants. Infection of plants occurs through two psyllid vectors, Diaphorina citri in Asia and Trioza eiytreae in Africa (3, 10). Today, despite many attempts

Nature of the greening bacterium-like organism (BLO) : taxonomic characterization by use of cloned DNA fragments

International audienc

Detection and characterization of the African citrus greening Liberobacter by amplification, cloning, and sequencing of the rplKAJL-rpoBC operon

International audienc

Expression of an ortholog of replication protein A1 (RPA1) is induced by gibberellin in deepwater rice

Internodes of deepwater rice are induced to grow rapidly when plants become submerged. This adaptation enables deepwater rice to keep part of its foliage above the rising flood waters during the monsoon season and to avoid drowning. This growth response is, ultimately, elicited by the plant hormone gibberellin (GA). The primary target tissue for GA action is the intercalary meristem of the internode. Using differential display of mRNA, we have isolated a number of genes whose expression in the intercalary meristem is regulated by GA. The product of one of these genes was identified as an ortholog of replication protein A1 (RPA1). RPA is a heterotrimeric protein involved in DNA replication, recombination, and repair and also in regulation of transcription. A chimeric construct, in which the single-stranded DNA-binding domain of rice RPA1 was spliced into the corresponding region of yeast RPA1, was able to complement a yeast rpa1 mutant. The transcript level of rice RPA1 is high in tissues containing dividing cells. RPA1 mRNA levels increase rapidly in the intercalary meristem during submergence and treatment with GA before the increase in the level of histone H3 mRNA, a marker for DNA replication