Monitoring of Genes Responding to Ionizing Radiation in Tradescantia

A species belonging to the genus Trandescantia has been studied as a sensitive plant to ionizing radiation. Purple color of the stamen hair stem has been reported to change to pink or white when it is exposed to radiation. In this study a hybrid clone BNL4430 was used to evaluate biological and genetical assays when exposed to gamma radiation. The gamma irradiation ranged from 50 to 1,000 mGy dose was achieved in the phytotron facility equipped with a 60 Co radiation source at the Korea Atomic Energy Research Institute, Korea. Dose-somatic pink response relationships were depicted by radiation intensities at days after treatment for two weeks. As expected greater color changes in stamen hair were detected with higher radiation dose and more stamen hair changed as days elapsed after treatment. An Illumina Hi-seq was used to profile differentially expressed genes responding to radiation intensities and 233,483 transcripts were obtained from the RNA-seq analysis. The average length of the transcripts was 1,229 bp and length for N50 was 1,808 bp. A total of 347 and 314 up- or down-regulated genes were annotated at the lowest dose 50 mGy, respectively. The genes showing two-fold change were categorized by their functions in the gene ontology (GO) analysis. Many up-regulated genes at 50mGy compared with non-radiation control were heat-shock protein family that was reported to protect protein function or folding. Reverse transcripted PCR (RT-PCR) and real-time RT PCR were performed to validate gene expression, which were collectively used to evaluate gene potential as an in situ monitoring tool for any radiation exposure.