Extensive changes in DNA methylation patterns accompany activation of a silent T-DNA ipt gene in Agrobacterium tumefaciens-transformed plant cells.

AUTOR(ES)

John, M C

RESUMO

We crossed a male-sterile, Agrobacterium-transformed Nicotiana tabacum plant that contains a silent, hypermethylated T-DNA ipt oncogene with a normal tobacco plant and found that the methylated state of the ipt gene was stably inherited through meiosis in the offspring. However, when tissues of these plants were placed in cell culture, the ipt gene was spontaneously reactivated in a very small fraction of the cells; if 5-azacytidine was added to the culture medium, ipt gene reactivation occurred at high frequency. We analyzed the pattern of DNA methylation in a region spanning the ipt gene in a line that does not express the ipt gene, in five derivatives of this line that reexpressed the ipt gene either spontaneously or after 5-azacytidine treatment, and in tissues of a sibling of this line that reexpressed ipt spontaneously. We found that the ipt locus was highly methylated in the unexpressed state but that spontaneous or 5-azacytidine-induced reexpression always resulted in extensive demethylation of a region including 5' upstream, coding, and 3' downstream regions of the ipt gene. The role of DNA methylation in gene regulation in this system is discussed.

Documentos Relacionados

• Delivery of T-DNA from the Agrobacterium tumefaciens chromosome into plant cells
• Methylation of the T-DNA in Agrobacterium tumefaciens and in several crown gall tumors.
• Temperature affects the T-DNA transfer machinery of Agrobacterium tumefaciens.
• T-DNA of Agrobacterium tumefaciens encodes an enzyme of cytokinin biosynthesis.
• Genetic analysis of the virD operon of Agrobacterium tumefaciens: a search for functions involved in transport of T-DNA into the plant cell nucleus and in T-DNA integration.