We carried out to study the function of ArgE in transgenic rice plants, which were confirmed by PCR analysis and hygromycin selection. Transgenic rice plants were with selectable marker gene(HPT) inserted in genome of the rice. Southern analysis with hpt probe confirmed by two restriction enzymes that copy numbers of the selectable gene was introduced into the plant genome. We displayed that the relationship between drought stress and ArgE gene with the overexpressing rice plants. From this result, we observed that the degree of leaves damage has no difference in control and transgenic lines. The total RNAs were extracted from 6 weeks-seedling in normal condition in order to examine their expression levels with ArgE-overexpressed transgenic rice. In particular, expression patterns of genes encoding enzymes involved in abiotic stress, including drought and salt stresses. OsGF14a and OsSalt were investigated by reverse transcription-PCR(RT-PCR). Expression levels of the OsSalt gene decreased significantly in transgenic rice plants compared to control plant. However, ion leakage measurement did not demonstrate any leaves damage change between control and ArgE transgenic plants exposure to mannitol treatment. These results suggest that expression of the ArgE is not involved in tolerance for drought stress in rice but may playa role of signaling networks for salt-induced genes.

Ornithine deacetylase (argE) gene as a negative selection marker gene was successfully co-transformed with SOD-APX or NDPK2 as a target gene to develop marker free transgenic rice. E.coli argE gene encodes an enzyme which activates N-acetyl phosphinothricin (N-AcPt) through deacetylation. The enzyme was reported that deacetylate N-AcPt, a non cyto-toxic compounds, to produce cyto-toxic PPT. So the argE gene can be used as a negative selection marker and N-AcPt can be used as a substrate of argE gene. Using former purification method (Kriete G., et al., 1996) was very expensive because the small amount of N-AcPt produced by the method. We developed a strategy to produce N-AcPt by means of chemical method. N-AcPt function was identified using hygromycin resistant T1 seeds on MS basal medium contained N-AcPt prior to utilization of argE gene as a negative selection marker in marker free transgenic rice. Negative selection effects were performed with T1 seeds containing argE gene under N-AcPt. This system provides a efficient negative selection effect from transgenic rice and that will be efficiently used for the production of marker gene free rice plants.

Agronomic characteristics of transgenic herbicide-resistant rice lines were evaluated under field condition. Differences in agronomic traits and rice quality were observed between transgenic plants and the corresponding untransformed controls. Transgenic Ilpumbyeo lines flowered earlier than untransformed controls, whereas transgenic Nagdongbyeo flowered at the same time as untransformed control. With regard to the yield and rice quality, most of the transgenic lines showed lower yield than control except some selected transgenic lines. Selected Nagdongbyeo transgenic line also showed good eating quality comparable to the control although most selected Ilpumbyeo transgenic lines showed slightly lower eating quality and increased white center/belly in the rice grain. In order to find the main factor leading to somaclonal variation among transgenic lines, Tos17, a rice retrotransposon activated by prolonged tissue culture period was investigated. Although the transgenic lines carried only one or two of transformed bar gene, the copy number of Tos17 increased in most transgenic lines compared with control. The activation of Tos17 was not detected in selected promising transgenic lines such as ND115-15-1-B and IP23-3-3, suggesting that the increased copy number of Tos17 may have negatively affected agronomic characteristics of transgenic rice.