Redox regulation of the cell cycle in Arabidopsis thaliana

Seed germination is critical for plant establishment but little is known about how the reduction-oxidation (redox) environment of the cells in the emerging root meristem influences cell division. The glutathione redox potentials of the nuclei and cytosol were determined using redox-sensitive green fluorescent protein (roGFP2) in the Arabidopsis root apical meristem, in which cell cycle had been synchronised using hydroxyurea, within the period immediately after germination, in order to characterise the relationships between cellular redox status and cell cycle progression. The average glutathione redox potentials of the nuclei and cytosol were -297.5 mV ± 0.7 and -292.8 mV ± 0.6 respectively. However, a transient oxidation occurred in compartments during the G1 phase of the cell cycle, as determined by the expression of cell cycle markers (CYCB1;1-GUS, cytrap and cyclins). The effect of low antioxidant buffering capacity on the gene expression profiles of dry and imbibed seeds as well as the redox potentials of the nuclei and cytosol was determined using the ascorbate deficient vtc2-1 and vtc2-4 mutants. The glutathione redox potentials of the nuclei in the proliferation zone of vtc2-1 radicles expressing roGPF2 were -282.3 mV ± 0.5 and the cytosol was -282.9 mV ± 0.5. These increased levels of oxidation persisted throughout the period of measurement, a feature that was linked to changes in cell cycle progression. The transcriptome profiles of vtc2-1 and vtc2-4 dry seeds compared with that of wild-type seeds revealed large changes in the abundance of transcripts encoding transcription factors, redox components, and proteins involved in cell cycle and secondary metabolism. Fewer differences were shown for the transcriptome profiles of vtc2-1 and vtc2-4 imbibed seeds. Taken together these data show that antioxidant buffering capacity exerts a strong influence on cell cycle progression and gene expression without having marked effects on germination.