Gene silencing induced by cytosine methylation in transgenic tomato = 형질전환 토마토에서 cytosine methylation에 의한 유전자발현 억제

Abstract

Transgene expression was analyzed in tomato plants. Four lines of neomycin phosphotransferase II gene (NPTII) and the trehalose biosynthetic fusion gene (TPSP) transformed T0 plants showed kanamycin resistance on selection medium. However, the analysis of phenotype (kanamycin resistance) and mRNA expression in T1 plants indicated that the expression of the NPTII and TPSP transgenes was down-regulated to an undetectable level in two independent lines 1 and 11. Southern analysis demonstrated that the lines 1 and 11 had multicopies of the transgenes, whereas the typical transgenic lines 2 and 10 had 1 or 2 copies. DNA methylation analysis using methylation sensitive enzyme detected accumulated CpG DNA methylation on TPSP coding region and CaMV35S promoter region in the line 11, but not the typical transgenic line 2. These results suggest that multicopy transgene in plants is attributed to down-regulation of the transgene expression via transcriptional gene silencing.