Treatment with Propionic and Butyric Acid Enhances Expression Variegation and Promoter Methylation in Plant Transgenes

Lohuis, Michael ten; Galliano, H.; Heidmann, Iris; Meyer, Peter

doi:10.1515/bchm3.1995.376.5.311

Cited by 16 publications

(1 citation statement)

References 40 publications

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“…All 7-repeat-containing transgenic events analyzed (pEN-MS1 and pEN-MS2) showed similar DNA methylation patterns compared to each other and also to that of the maize transgenes with seven repeats (Figure 4A). Such uniformity among transgenic events is unusual as methylation patterns between independent transgenic events are typically more variable [30]–[33]. The transgenic events carrying four and three b1 repeats (pEN-MS3 and pEN-MS4) also displayed low methylation levels within the repeats, but there was more variation between the different independent transgenic events (Figure 7B and 7C, and data not shown), similar to that seen for the endogenous maize three-repeat allele [19].…”

Section: Resultssupporting

confidence: 52%

Specific Tandem Repeats Are Sufficient for Paramutation-Induced Trans-Generational Silencing

et al. 2013

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Paramutation is a well-studied epigenetic phenomenon in which trans communication between two different alleles leads to meiotically heritable transcriptional silencing of one of the alleles. Paramutation at the b1 locus involves RNA-mediated transcriptional silencing and requires specific tandem repeats that generate siRNAs. This study addressed three important questions: 1) are the tandem repeats sufficient for paramutation, 2) do they need to be in an allelic position to mediate paramutation, and 3) is there an association between the ability to mediate paramutation and repeat DNA methylation levels? Paramutation was achieved using multiple transgenes containing the b1 tandem repeats, including events with tandem repeats of only one half of the repeat unit (413 bp), demonstrating that these sequences are sufficient for paramutation and an allelic position is not required for the repeats to communicate. Furthermore, the transgenic tandem repeats increased the expression of a reporter gene in maize, demonstrating the repeats contain transcriptional regulatory sequences. Transgene-mediated paramutation required the mediator of paramutation1 gene, which is necessary for endogenous paramutation, suggesting endogenous and transgene-mediated paramutation both require an RNA-mediated transcriptional silencing pathway. While all tested repeat transgenes produced small interfering RNAs (siRNAs), not all transgenes induced paramutation suggesting that, as with endogenous alleles, siRNA production is not sufficient for paramutation. The repeat transgene-induced silencing was less efficiently transmitted than silencing induced by the repeats of endogenous b1 alleles, which is always 100% efficient. The variability in the strength of the repeat transgene-induced silencing enabled testing whether the extent of DNA methylation within the repeats correlated with differences in efficiency of paramutation. Transgene-induced paramutation does not require extensive DNA methylation within the transgene. However, increased DNA methylation within the endogenous b1 repeats after transgene-induced paramutation was associated with stronger silencing of the endogenous allele.

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Section: Resultssupporting

confidence: 52%

Specific Tandem Repeats Are Sufficient for Paramutation-Induced Trans-Generational Silencing

et al. 2013

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Gene Expression and Level of Expression

Buck

Depicker

2004

Handbook of Plant Biotechnology

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Genes encoding heterologous proteins are introduced into the plant genome for several purposes. First, the plant‐made protein can be a tool in fundamental research. Second, the synthesis of heterologous proteins in plants can have biotechnological applications. Plants are capable of producing several types of recombinant proteins. Indeed, for the production of all these proteins, the use of plants is obvious, because they have several important advantages; plants can grow easily and inexpensively in large quantities and they can be harvested and processed with the available agronomic infrastructures and upscaling is very simple. Finally, using processes similar to those used in food and feed industry, specifically desired proteins can be easily purified. However, the stability of accumulation is as important as the accumulation levels themselves. Indeed, the introduced transgenes are not always correctly expressed and are often susceptible to position effects and homology‐dependent gene silencing (HDGS) mechanisms. Although the mechanism that induces silencing is still not completely unravelled, already some factors are defined which influence transgene expression, such as copy number and chromosomal position, methylation pattern in the integration region and properties of the transgene sequence itself.

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