Biomedical subjects

John Antoniw

Publications and source records attributed to John Antoniw.

5 recordsLinked to original sources

PubMed2006

Genome and EST analyses and expression of a gene family with putative functions in insect chemoreception.

Odorant-binding proteins (OBPs) are thought to be responsible for the transport of semiochemicals across hydrophobic interfaces to olfactory receptors. In insects, a second class of OBPs with four conserved cysteines has been variously named as sensory appendage proteins, olfactory segment-D proteins, and chemosensory proteins (CSPs). The physiological functions of these proteins have remained elusive. Here we report a comprehensive survey of both genome and expressed sequence tags (EST) databases. This showed that CSPs are apparently only present in the phylum, Arthropoda, and in two subphyla, Crustacea and Uniramia. This is the first report of a putative CSP in Crustacea and suggests that the origin of these genes predates the divergence of Uniramia and Crustacea. For the Uniramia, we identified 74 new genes encoding putative CSPs of insect species from 10 different orders. Using tissue-specific EST libraries, we have examined the relative expression of putative CSP genes in many tissues from 22 insect species suggesting that the genes are expressed widely. One Drosophila CSPs is expressed sixfold higher in head than other CSPs. One Bombyx mori CSPs was found at a very high level in pheromone gland, and for the first time, six CSPs were identified in B. mori compound eyes. The different frequencies of CSP transcripts were observed between solitary and gregarious EST libraries of Locusta migratoria.

Animals↗

PubMed2005

Ascorbic acid deficiency activates cell death and disease resistance responses in Arabidopsis.

Programmed cell death, developmental senescence, and responses to pathogens are linked through complex genetic controls that are influenced by redox regulation. Here we show that the Arabidopsis (Arabidopsis thaliana) low vitamin C mutants, vtc1 and vtc2, which have between 10% and 25% of wild-type ascorbic acid, exhibit microlesions, express pathogenesis-related (PR) proteins, and have enhanced basal resistance against infections caused by Pseudomonas syringae. The mutants have a delayed senescence phenotype with smaller leaf cells than the wild type at maturity. The vtc leaves have more glutathione than the wild type, with higher ratios of reduced glutathione to glutathione disulfide. Expression of green fluorescence protein (GFP) fused to the nonexpressor of PR protein 1 (GFP-NPR1) was used to detect the presence of NPR1 in the nuclei of transformed plants. Fluorescence was observed in the nuclei of 6- to 8-week-old GFP-NPR1 vtc1 plants, but not in the nuclei of transformed GFP-NPR1 wild-type plants at any developmental stage. The absence of senescence-associated gene 12 (SAG12) mRNA at the time when constitutive cell death and basal resistance were detected confirms that elaboration of innate immune responses in vtc plants does not result from activation of early senescence. Moreover, H2O2-sensitive genes are not induced at the time of systemic acquired resistance execution. These results demonstrate that ascorbic acid abundance modifies the threshold for activation of plant innate defense responses via redox mechanisms that are independent of the natural senescence program.

Antioxidants↗

PubMed2005

Analysis of expressed sequence tags from the wheat leaf blotch pathogen Mycosphaerella graminicola (anamorph Septoria tritici).

Mycosphaerella graminicola is a major fungal pathogen of wheat as the causal agent of Septoria leaf blotch disease. As a first step toward a greater understanding of the mechanism of host infection we have generated, sequenced, and analyzed three M. graminicola EST libraries from conditions predicted to resemble independent phases of the host infection process, including one library generated from the fungus during interaction with its host. A total of 5180 ESTs were sequenced and clustered into 886 contigs and 2039 singletons to give a set of 2925 unique sequences (unisequences). BLASTX analysis revealed 33% of the unknown M. graminicola unisequences to be orphans. Very limited inter-library overlap of expression was seen with the majority of unisequences (contigs and singletons) being library-specific. Analysis of EST redundancy between libraries demonstrated a significant difference in gene expression in the three conditions. Comparisons made against fully sequenced genomes revealed most M. graminicola sequences to be homologous to genes present in both pathogenic and non-pathogenic Ascomycete filamentous fungi. A range of sequences having significant homology to verified pathogenicity/virulence genes (HvPV-genes) of either plant or mammalian fungal and Oomycete pathogens were also identified (<1e-20). The generation of, and the diversity present within, this EST collection will facilitate future efforts aimed at a more detailed study of the transcriptome of the fungus during host infection.

Ascomycota↗

PubMed2003

Effects of leaf ascorbate content on defense and photosynthesis gene expression in Arabidopsis thaliana.

Ascorbate deficiency in the Arabidopsis thaliana vtc1 mutant had no effect on photosynthesis, but modified defense pathways. The ascorbate content of vtc1 leaves was increased 14-fold after 10 mM ascorbate was supplied, without a concomitant change in redox state. High ascorbate modified the abundance of 495 transcripts. Transcripts encoding dehydroascorbate reductase, pathogenesis-related protein 1, and a peroxiredoxin were decreased, whereas those encoding salicylate induction-deficient protein 1, Cu,Zn superoxide dismutase, iron superoxide dismutase, metallothionein, and glutathione transferases were increased. Catalase transcripts were unaffected, but ascorbate peroxidase isoforms APX1 and tAPX were slightly decreased and sAPX transcripts increased. A number of nuclear encoded transcripts for photosynthetic electron transport components were repressed as a result of ascorbate accumulation, whereas those that were chloroplast-encoded were increased. High ascorbate caused decreases in mRNAs encoding chloroplast enzymes such as fructose-1,6-bisphosphatase and sedoheptulose-1,7-bisphosphatase that are activated by reduced thioredoxin. In contrast, others, such as glucose 6-phosphate dehydrogenase, whose activity is inactivated by reduced thioredoxin, were repressed. Together, these results show that ascorbate is involved in metabolic cross-talk between redox-regulated pathways. The abundance of this antioxidant provides information on redox buffering capacity that coordinates redox processes associated with the regulation of photosynthesis and plant defense.

Antioxidants↗

PubMed2003

Leaf vitamin C contents modulate plant defense transcripts and regulate genes that control development through hormone signaling.

Vitamin C deficiency in the Arabidopsis mutant vtc1 causes slow growth and late flowering. This is not attributable to changes in photosynthesis or increased oxidative stress. We have used the vtc1 mutant to provide a molecular signature for vitamin C deficiency in plants. Using statistical analysis, we show that 171 genes are expressed differentially in vtc1 compared with the wild type. Many defense genes are activated, particularly those that encode pathogenesis-related proteins. Furthermore, transcript changes indicate that growth and development are constrained in vtc1 by the modulation of abscisic acid signaling. Abscisic acid contents are significantly higher in vtc1 than in the wild type. Key features of the molecular signature of ascorbate deficiency can be reversed by incubating vtc1 leaf discs in ascorbate. This finding provides evidence that many of the observed effects on transcript abundance in vtc1 result from ascorbate deficiency. Hence, through modifying gene expression, vitamin C contents not only act to regulate defense and survival but also act via phytohormones to modulate plant growth under optimal conditions.

Abscisic Acid↗