Implantation with low-energy N+ Beam Changes the Transcriptional Activation of the Expression Sequence Tags (ESTs) from the Transposable Elements in Rice

Abstract

Transposable elements (TEs) have played important roles in the evolution of the genes and genomes. As a new resource of mutagens, low-energy ion beam implantation is characterized as slightly physiological damages, wide mutation spectrum, and high mutation frequency comparing with other mutagenicity methods. In order to shed light on the expression profiles of the functional genes from the transposons responding to the stress of the ion-beam radiation, we have investigated the transcriptome features of rice implanted with the nitrogen-ion-beam implantation, using the Agilent Rice Oligo Microarray (4×44K) Genome Array including more 40,000 encoding expression sequence tags (ESTs), involving 177 ESTs from TEs. The results show that there are 982 differentially expressed genes (fold changei¼ž2 and P valuei¼œ0.05) in rice seedlings underlying the implantation of the nitrogen ion beam, including 429 up-regulated transcripts and 553 down-regulated transcripts, underlying the implantation of the lower-energy nitrogen beam. The gene ontology enrichment analysis shows that the up-regulated genes are statistically significant (P valuei¼œ0.05) clusterred into five molecular functions GO terms, three cellular component GO terms and one metabolic process GO terms. The down-regulated genes are statistically significant (P valuei¼œ0.05) clusterred into ten molecular functions GO terms, nineteen metabolic process GO terms, but no cellular component GO terms. The results showed that 42 ESTs, including the functional transposase, intergrase, conserveddeoxyribonucleic acid deoxyribonucleic acid (DNA) transposon protein, retrotransposon pol and viral coat and capsid protein, are expressed differentially, comprising 24% the total transposable elements ESTs in the genechip expression data. Most of these differential expression ESTs are up-regulated or re-activated, which provide more transposable potentiality to the TEs. These results imply that the increased potentiality of the transposition of the TEs is contributed to the biological effects of the low-energy-ion-beam implantation. These results provide the profiles of the differentially expressed genes and the fundamental relation between the TEs in plants and the implantation of the ion beam. Key words: Implantation of the ion beam, transposable elements, transcriptional activation, rice.