DNA microarray technology was applied to gain insight into the role of the redox state of PQ pool as a retrograde factor mediating differential expression of Arabidopsis nuclear genes during the acclimation to changing irradiance. DNA microarray chips containing probes corresponding to 24000 Arabidopsis nuclear genes were screened with cRNA samples prepared from leaves of plants exposed for 5 h to low irradiance (control) vs. medium, high and excessive irradiances (MI, HI and EI, respectively). Six hundred and sixty three genes were differentially expressed as a result of an exposure to at least one elevated irradiance. Among 663 differentially expressed genes a total of 50 were reverted by DCMU - 24 ones modulated at medium irradiance, 32 ones modulated at high irradiance and a single one modulated at excessive irradiance. We postulate that their expression is regulated by redox state of plastoquinone (PQ) pool. Thus the PQ-mediated redox regulation of expression of Arabidopsis nuclear genes is probably limited to the irradiance window representing non-stressing conditions. We found that the promoter regions of the PQ-regulated genes contained conserved elements, suggesting transcriptional control by a shared set of trans-acting factors which participate in signal transduction from the redox state of the PQ pool.
The plant Solanum nigrum treated with the pathogen Phytophthora infestans-de- rived elicitor responded by elevated reactive oxygen species (ROS) production, lipid peroxidation and lipoxygenase (EC 1.13.11.12) activity in comparison with control plants indicating that oxidative stress took place. We demonstrate that these events are accompanied by a significant increase in plastoquinone (PQ) level. It is postulated that PQ may be associated with mechanisms maintaining a tightly controlled balance between the accumulation of ROS and antioxidant activity that determines the full expression of effective defence.
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