Abstract
The effect of long-term continuous irradiation has relevance to study in radiation ecotoxicology. For investigation of biological responses to continuous irradiation in plants, we assessed gene expression in a model plant arabidopsis. Microarray analysis revealed 56 up-regulated genes in the plants exposed to gamma rays for 2 weeks at a dose rate of 20 Gy/day. The genes up-regulated by the irradiation could be classified into two types by the time-dependent expression patterns; early-responsive genes which responded within 1 day, and late-responsive genes which responded 3-7 days after the start of the continuous irradiation. The former type included some genes relating to DNA repair, whereas the latter other genes relating to protein and carbohydrate metabolism. Each type also included different genes of signal transduction and transcriptional control. These behaviors of gene expression probably reflect the responses of the plants to cope with progression of radiation damages. We compared the gene expression profile with those in previous studies not only about radiation effect but also other environmental stresses, to speculate biological responses relating to the damages on plant growth by continuous irradiation.
