Plant, Animal & Microbe Genomes X Conference Plant, Animal & Microbe Genomes X ConferenceJanuary 12-16, 2002
Town & Country Convention Center
San Diego, CA
Workshop: Organellar Genetics
Plant mitochondria exhibit two electron transport pathways; the cytochrome (oxidase) pathway and an alternative oxidase (AOX) path. AOX shows increased expression under stress conditions, especially under oxidative stress. In Arabidopsis, AOX is encoded by a small family of genes of which at least one is predominantly transcribed in leaves in response to reactive oxygen species (ROS). To date, it has not been feasible to broadly elucidate the elements of mitochondrion-nucleus communication in plants. The missing component has been a scorable trait for mitochondrial function, one responsive to environmental signals. Under controlled growth conditions AOX is a dispensable activity in plant cells, thus its levels may be genetically modified and potential mutants lacking AOX activity recovered. We have used a visual screen for impaired AOX induction following challenge by oxidative stress and putative mutant rescue to isolate a number of AOX mutant lines from Arabidopsis. To complement this screen, microarray analysis has been employed to further characterize these mutants, stably transformed sense- and antisense AOX plants, and to profile genes and gene clusters involved in stress-induced AOX expression. Interestingly, while a large number of genes show expression changes in response to ROS, only relatively few of these produce mitochondrion-targeted gene products. Further studies using Arabidopsis cell cultures have shown they respond to ROS in a similar manner, AOX induction, as both cultured tobacco cells and Arabidopsis leaves. We have initiated a mitochondrial proteome project to investigate the proteins present in plant mitochondrial membranes and matrix fractions, and to profile changes during ROS challenge.