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M Bonafede

Publications and source records attributed to M Bonafede.

4 recordsLinked to original sources
PubMed2006

The wheat and barley vernalization gene VRN3 is an orthologue of FT.

Winter wheat and barley varieties require an extended exposure to low temperatures to accelerate flowering (vernalization), whereas spring varieties do not have this requirement. In this study, we show that in these species, the vernalization gene VRN3 is linked completely to a gene similar to Arabidopsis FLOWERING LOCUS T (FT). FT induction in the leaves results in a transmissible signal that promotes flowering. Transcript levels of the barley and wheat orthologues, designated as HvFT and TaFT, respectively, are significantly higher in plants homozygous for the dominant Vrn3 alleles (early flowering) than in plants homozygous for the recessive vrn3 alleles (late flowering). In wheat, the dominant Vrn3 allele is associated with the insertion of a retroelement in the TaFT promoter, whereas in barley, mutations in the HvFT first intron differentiate plants with dominant and recessive VRN3 alleles. Winter wheat plants transformed with the TaFT allele carrying the promoter retroelement insertion flowered significantly earlier than nontransgenic plants, supporting the identity between TaFT and VRN-B3. Statistical analyses of flowering times confirmed the presence of significant interactions between vernalization and FT allelic classes in both wheat and barley (P < 0.0001). These interactions were supported further by the observed up-regulation of HvFT transcript levels by vernalization in barley winter plants (P = 0.002). These results confirmed that the wheat and barley FT genes are responsible for natural allelic variation in vernalization requirement, providing additional sources of adaptive diversity to these economically important crops.

Adaptation, Physiological↗
PubMed2001

CD11b expression identifies CD8+CD28+ T lymphocytes with phenotype and function of both naive/memory and effector cells.

A previously unreported CD8(+)CD28(+)CD11b(+) T cell subset occurs in healthy individuals and expands in patients suffering from primary viral infections. In functional terms, these cells share the features of naive/memory CD8(+)CD28(+)CD11b(-) and terminally differentiated effector CD8(+)CD28(-)CD11b(+) subpopulations. Like CD28(-) cells, CD28(+)CD11b(+) lymphocytes have the ability to produce IFN-gamma, to express perforin granules in vivo, and to exert a potent cytolytic activity. Moreover, these cells can respond to chemotactic stimuli and can efficiently cross the endothelial barrier. In contrast, like their CD11b(-) counterpart, they still produce IL-2 and retain the ability to proliferate following mitogenic stimuli. The same CD28(+)CD11b(+) subpopulation detected in vivo could be generated by culturing naive CD28(+)CD11b(-) cells in the presence of mitogenic stimuli following the acquisition of a CD45RO(+) memory phenotype. Considering both phenotypic and functional properties, we argue that this subset may therefore constitute an intermediate phenotype in the process of CD8(+) T cell differentiation and that the CD11b marker expression can distinguish between memory- and effector-type T cells in the human CD8(+)CD28(+) T cell subset.

CD28 Antigens↗
PubMed2000

High-level expression of chromosomally encoded SHV-1 beta-lactamase and an outer membrane protein change confer resistance to ceftazidime and piperacillin-tazobactam in a clinical isolate of Klebsiella pneumoniae.

We describe Klebsiella pneumoniae 15571, a clinical isolate resistant to ceftazidime MIC = 32 microg/ml) and piperacillin-tazobactam (MICs = 1,024 and 128 microg/ml). K. pneumoniae 15571 expresses a single beta-lactamase with a pI of 7.6. However, when cloned in a high-copy-number vector in Escherichia coli, this bla(SHV-1) gene did not confer resistance to ceftazidime, a spectrum consistent with the nucleotide sequence, which was nearly identical to those of previously described bla(SHV-1) genes. Outer membrane protein (OMP) analysis of K. pneumoniae 15571 revealed a decrease in the quantity of a minor 45-kDa OMP in comparison to that in K. pneumoniae 44NR, a low-level ampicillin-resistant strain that also expresses a chromosomally determined bla(SHV-1). Crude beta-lactamase enzyme extracts from K. pneumoniae 15571 produced roughly 200-fold more beta-lactamase activity than K. pneumoniae 44NR. Northern hybridization analysis revealed that this difference was explainable by quantifiable differences in transcription of the bla(SHV-1) gene in the two strains. Primer extension analysis of bla(SHV-1) mRNA from K. pneumoniae 15571 and 44NR indicated that the transcriptional start sites were identical in the two strains. DNA sequencing of the promoter regions upstream of the of bla(SHV-1) open reading frames in the two K. pneumoniae strains revealed an A-->C change in the second position of the -10 region in K. pneumoniae 44NR compared to that in 15571. Site-directed mutagenesis of the cloned K. pneumoniae 15571 bla(SHV-1), in which the A in the second position of the 15571 -10 region was changed to a C, resulted in a substantial lowering of the MIC of ampicillin. When the levels of beta-lactamase enzyme expression in E. coli were compared, the bla(SHV-1) downstream of the altered -10 region produced 17-fold less beta-lactamase enzyme. These results indicate that elevated levels of ceftazidime resistance can result from a combination of increased enzyme production and minor OMP changes and that levels of chromosomally encoded SHV-1 beta-lactamase production can vary substantially with a single-base-pair change in promoter sequence.

Bacterial Outer Membrane Proteins↗