An investigation into the role of cytosolic free Ca2+ in Salicylic acid mediation of disease resistance in Arabidopsis

Petersen, Lindsay Natalie

An investigation into the role of cytosolic free Ca2+ in Salicylic acid mediation of disease resistance in Arabidopsis

Thesis / Dissertation

2001

Abstract

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.

Keywords

Molecular and Cell Biology

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