Analysis of methylation and post-transcriptional gene silencing in embryos and seedlings of C5, a transgenic Plum pox virus resistant plum Prunus domestica L.

摘要

We have previously shown that in the Plum pox virus (PPV)-resistant transgenic plum clone C5 the PPV-coat protein (CP) insert is post-transcriptionally silenced (PTGS) and methylated. The transgene insert and PPV resistance are mutually inherited in progeny of C5. In herbaceous systems, PTGS has been shown to be "re-set" following seed germination. To our knowledge, this phenomenon has not been studied in woody perennials. P. domestica is a woody perennial that normally requires stratification (moist chilling) for germination. Seeds of open-pollinated C5 carrying the PPV-CP insert were germinated with and without stratification, as were seeds of C3, a non-PTGS PPV-CP transgenic clone that is susceptible to PPV. DNA analyses showed that at one month following germination the PPV-CP gene in C5 was methylated in seedlings from both stratified and non-stratified treatments at levels comparable to the levels in leaves of the C5 parent, whereas the nptII and uidA transgenes were unmethylated as expected. No transgene methylation was found in C3 seedlings. These results demonstrate the early expression of PPV-CP transgene methylation in seedlings of the C5 PPV-resistant plum clone.