Genetics - Theses
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ItemInvestigating the mechanisms of zinc homeostasis in Arabidopsis thaliana(University of Melbourne, 2010)Zn is an element essential for all forms of life, and either Zn-deficiency or excess Zn can have serious biological consequences. In plants, Zn levels are controlled by a number of physiological and cellular mechanisms to maintain appropriate physiological concentrations of Zn. This study further characterises the HMA2 and HMA4 transporters by developing a novel technique using the Zn fluorophore Zinpyr-1. A procedure for the use of Zinpyr-1 in Arabidopsis roots was developed and validated which allowed the visualisation and relative quantification of Zn. This technique showed that both hma4 and hma2/hma4 mutants differed in the amount of Zn and its distribution compared to wildtype or hma2. This correlates to previous data showing that hma4 and hma2/hma4 are Zn-deficient in shoots but accumulate Zn in roots. Thus we can say that this Zn- deficiency in shoot occurs due to an inability to load Zn into the xylem for transport to the shoot. To investigate the regulation of Zn-homeostasis, Zn-deficient and hma2/hma4 plants were compared to wildtype in micro-array experiments to test whether plants respond systemically to Zn- deficiency. hma2/hma4 plants are Zn-deficient in shoots but over-accumulate Zn in roots, so genes co-regulated in hma2/hma4 roots and shoots, and genes co-regulated in hma2/hma4 roots and Zn- deficient wildtype roots were identified. 52 and 27 genes were identified in these comparisons respectively as regulated >2-fold in the same direction. These were considered robust as their co-regulation was observed in four measurements, two technical replicates of two biological replicates. promoter