@phdthesis{oai:tsukuba.repo.nii.ac.jp:00020918,
 author = {光原, 一朗 and Mitsuhara, Ichiro},
 month = {},
 note = {The identification of the functions of a particular gene by overexpression or suppression is a common procedure in modern molecular bioloby. However,the expression level of foreign genes is sometimes insufficient in plants. To solve this problem,a series of chimeric promoters for high-level expression of foreign genes in plants were constructed as fusion constructs with the β-glucuronidase(GUS)gene and the activity of these promoters was assayed in tobacco and rice. As promoters,the CaMV 35S core promoter,three different 5'-upstream sequences of the 35S promoter,the first intron of the gene for phaseolin,and a 5'-untranslated sequence of tobacco mosaic virus (Ω sequence) were used in various combinations. Some chimeric promoters showed levels of GUS activity that were 20-and 70-fold higher than those obtained with the 35S promoter in pBI221 in tobacco and rice,respectively.

When the representative promoter E12Ω was introduced into tobacco with the gene for luciferase,the autofluorescence of the detached leaves was great and easily detectable by the naked eye in a dark room. However,latter generations of the transgenic tobacco plants containing the E12Ω-LUC chimeric gene frequently exhibited post-transcriptional gene silencing (PTGS) of the luc transgene. As PTGS can suppress both the transgene and endogenous genes with considerable homology to the transgene,the promoter may be useful not only for overexpression but also for suppression of a particular gene by single transformation of a construct which overdrives the gene. Indeed,the ACC oxidase (ACO) gene was overexpressed and suppressed by the introduction of the E12Ω-ACO fusion gene.

In plants,programmed cell death (PCD)-like events have been reported,although little is known of the mechanism at the molecular level. To elucidate whether the cell death mechanism is conserved between animals and plants,Bcl-xL and Ced-9,suppressors of PCD in humans and nematodes,were overproduced in tobacco plants using the strong promoter E12Ω. In Bcl-xL and Ced-9 expressers,cell death induced by UV-B irradiation,paraquat treatment and the N gene-dependent hypersensitive reaction (HR) upon tobacco mosaic virus infection was suppressed depending on the amount of foreign protein. Caspase,which is known as a cell death-executing protease,-like activity was transiently induced upon HR and the induction was suppressed in the Bcl-xL expresser. Furthermore,the expression of P35,which suppresses animal cell death by inhibiting caspase activiy,also suppressed plant cell death induced by UV and paraquat treatment. These results suggest that signaling pathways of cell death in plant and animal kingdoms are conserved., 2001, Includes bibliographical references, 著者の希望により要旨のみ公開},
 school = {筑波大学, University of Tsukuba},
 title = {Analysis of self-defense mechanisms using tobacco mosaic virus-infected tobacco leaves},
 year = {2002}
}