Browsing by Author "Petersen, Lindsay Natalie"

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    An investigation into the role of cytosolic free Ca2+ in Salicylic acid mediation of disease resistance in Arabidopsis
    (2001) Petersen, Lindsay Natalie; Denby, Katherine J
    Salicylic acid (SA) accumulation upon pathogen attack is a fundamental requirement for the activation of numerous plant defence mechansms. Cytosolic free Ca2+ ([Ca2+]c) is a ubiquitous signalling molecule involved in a host of cellular processes. Using transgenic Arabidopsis thaliana seedlings expressing the Ca2+-sensitive photoprotein aequorin, we previously reported a rapid and transient increase in [Ca2+]c upon application of exogenous SA. We now investigated the characteristics of the SA-induced [Ca2+]c increase and report that the majority of the response is derived from internal stores. It appears likely that SA triggers Ca2+-induced Ca2+-release. Preliminary evidence suggests a role for the SA-induced [Ca2+]c increase in the regulation of NPR1 expression since modulation of the SA-induced [Ca2+]c response with the extracellular Ca2+ chelator BAPTA causes a reduction in NPR1 mRNA levels. We have isolated two putative mutants that are defective in their ability to produce a SA-induced [Ca2+]c increase. Characterisation of these mutants is underway and will prove invaluable in identifying the components or events that cause the SA-induced [Ca2+]c transient, thereby aiding in the understanding of the role of [Ca2+]c in SA-mediated signal transduction.
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    The regulation and role of oxidative signal-inducible 1 protein kinase in Arabidopsis thaliana
    (2007) Petersen, Lindsay Natalie; Denby, Katherine J; Knight, Marc
    This study attempted to further characterise OXI1 protein kinase. Confocal microscopy and subcellular fractionation studies revealed a cytosolic localisation pattern for OXI1. Employment of a bioinformatics approach confirmed the induction of OXI1 gene expression in response to a range of AOS generating stimuli. However, the transcriptional increase of OXI1 in response to salinity and heat appears to be of no biological significance since the oxi1 mutant did not display altered tolerance to these two stresses in comparison to wild type.