Matrix Attachment Regions and Transcriptional Gene Silencing

摘要: It was realized early in the history of transgenic work that expression genes transferred to plant genomes not always stable or predictable. Such variation has often been attributed position effects, such as those known occur Drosophila (Pal-Bhadra et al., 2004). Position effects are presumed reflect pre-existing differences chromatin structure other genomic features at different sites transgene integration. However, it is now clear also affected, and may even be blocked altogether (silenced), by mechanisms largely independent chromosomal integration site. For example, 1989 Matzke group reported inactivation methylation transgenes from a first transformation following second with another T-DNA. Soon thereafter, back papers Napoli al. (1990) van der Krol cosuppression homologous host genes, Lindbo (1993) transgene-induced virus resistance associated cytoplasmic activity targets specific RNA sequences for inactivation. Many subsequent reports have highlighted fact quite frequently subject silencing. One particularly dramatic example comes Meyer (1992), who set up an experiment designed trap transposons inserting into petunia. The maize A1 gene, white-flowered mutant petunia, conferred salmon-red color phenotype flowers. Transposon insertions inactivating should, therefore, create white sectors otherwise salmoncolored Expecting events rare, large field involving 30 000 individuals. Instead expected rare events, however, they found variety phenotypes, including fully variegated flowers, very high frequency. A few flowers were deletions transgene, but many others, showing variegation developmental shifts expression, status 35S promoter. likelihood seemed increase age which seed derived, well response several environmental factors temperature.