Biomedical subjects

Timothy W McNellis

Publications and source records attributed to Timothy W McNellis.

3 recordsLinked to original sources

PubMed2004

Transgenic expression of the von Willebrand A domain of the BONZAI 1/COPINE 1 protein triggers a lesion-mimic phenotype in Arabidopsis.

The copines are a newly identified, widely distributed class of Ca(2+)-dependent, phospholipid-binding proteins that may be involved in cellular signaling. The copines have a characteristic domain structure: two C2 domains in the N-terminal region and a von Willebrand A (VWA) domain in the C-terminal region. Studies suggest that copines interact with target protein(s) via their VWA domain and recruit the proteins to a membrane location through the activity of the C2 domains. Arabidopsis thaliana (L.) Heynh. plants with loss-of-function mutations in the BONZAI 1/COPINE 1 (BON1/CPN1) gene display aberrant regulation of defense responses, including development of a lesion-mimic phenotype, an accelerated hypersensitive response, and increased resistance to a bacterial and an oomycetous pathogen. The phenotype of mutants in BON1/CPN1 is both humidity- and temperature-sensitive. In this study, we generated transgenic plants expressing either the VWA or the C2 portions of BON1/CPN1 in the wild-type Columbia-0 (Col-0) genetic background. Transgenic plants expressing the BON1/CPN1 C2 domain portion appeared like wild-type plants. However, transgenic plants expressing the BON1/CPN1 VWA domain exhibited a lesion-mimic phenotype that partially phenocopied bon1/cpn1 mutant plants. Our data suggest that BON1/CPN1 VWA domain fragments may interfere with the function of the full-length endogenous BON1/CPN1 protein, possibly by competing with the full-length BON1/CPN1 protein for association with target proteins normally bound to the full-length BON1/CPN1 protein.

Arabidopsis↗

PubMed2003

Rootstock effects on gene expression patterns in apple tree scions.

Like many fruit trees, apple trees (Malus pumila) do not reproduce true-to-type from seed. Desirable cultivars are clonally propagated by grafting onto rootstocks that can alter the characteristics of the scion. For example, the M.7 EMLA rootstock is semi-dwarfing and reduces the susceptibility of the scion to Erwinia amylovora, the causal agent of fire blight disease. In contrast, the M.9 T337 rootstock is dwarfing and does not alter fire blight susceptibility of the scion. This study represents a comprehensive comparison of gene expression patterns in scions of the 'Gala' apple cultivar grafted to either M.7 EMLA or M.9 T337. Expression was determined by cDNA-AFLP coupled with silver staining of the gels. Scions grafted to the M.9 T337 rootstock showed higher expression of a number of photosynthesis-related, transcription/translation-related, and cell division-related genes, while scions grafted to the M.7 EMLA rootstock showed increased stress-related gene expression. The observed differences in gene expression showed a remarkable correlation with physiological differences between the two graft combinations. The roles that the differentially expressed genes might play in tree stature, stress tolerance, photosynthetic activity, fire blight resistance, and other differences conferred by the two rootstocks are discussed.

Amino Acid Sequence↗

PubMed2003

Regulation of Arabidopsis COPINE 1 gene expression in response to pathogens and abiotic stimuli.

The copines are a widely distributed class of calcium-dependent, phospholipid-binding proteins of undetermined biological function. Mutation of the Arabidopsis CPN1 (COPINE 1) gene causes a humidity-sensitive lesion mimic phenotype with increased resistance to a bacterial and an oomyceteous pathogen, constitutive pathogenesis-related gene expression, and an accelerated hypersensitive cell death defense response. Here, we show that the disease resistance phenotype of the cpn1-1 mutant was also temperature sensitive, demonstrate increased CPN1 gene transcript accumulation in wild-type plants under low-humidity conditions, and present a detailed analysis of CPN1 gene transcript accumulation in response to bacterial pathogens. In wild-type plants, CPN1 transcript accumulation was rapidly, locally, and transiently induced by both avirulent and virulent strains of Pseudomonas syringae pv tomato bacteria. However, induction of CPN1 transcript accumulation by avirulent bacteria was much faster and stronger than that induced by virulent bacteria. Bacterial induction of CPN1 transcript accumulation was dependent on a functional type III bacterial protein secretion system. In planta expression of the avrRpt2 avirulence gene was sufficient to trigger rapid CPN1 transcript accumulation. CPN1 transcript accumulation was induced by salicylic acid treatment but was not observed during lesion formation in the lesion mimic mutants lsd1 and lsd5. These results are consistent with CPN1 playing a role in plant disease resistance responses, possibly as a suppressor of defense responses including the hypersensitive cell death defense response. The results also suggest that CPN1 may represent a link between plant disease resistance and plant acclimation to low-humidity and low-temperature conditions.

Acclimatization↗