Endogenous and environmental factors influence 35S promoter methylation of a maize A1 gene construct in transgenic petunia and its colour phenotype

Abstract

30,000 transgenic petunia plants carrying a single copy of the maize A1 gene, encoding a dihydroflavonol reductase, which confers a salmon red flower colour phenotype on the petunia plant, were grown in a field test. During the growing season plants with flowers deviating from this salmon red colour, such as those showing white or variegated phenotypes and plants with flowers exhibiting only weak pigmentation were observed with varying frequencies. While four white flowering plants were shown at the molecular level to be mutants in which part of the A1 gene had been deleted, other white flowering plants, as well as 13 representative plants tested out of a total of 57 variegated individuals were not mutants but rather showed hypermethylation of the 35S promoter directing A1 gene expression. This was in contrast to the homogeneous fully red flowering plants in which no methylation of the 35S promoter was observed. While blossoms on plants flowering early in the season were predominantly red, later flowers on the same plants showed weaker coloration. Once again the reduction of the A1-specific phenotype correlated with the methylation of the 35S promoter. This variation in coloration seems to be dependent not only on exogenous but also on endogenous factors such as the age of the parental plant from which the seed was derived or the time at which crosses were made.

Stability of transgene expression in poplar: A model forest tree species

“…Nevertheless, it is interesting to note that -for both constructs -approximately half of the transgenic lines showed a reduction in transgene expression levels following transfer to greenhouse conditions. Such an observation is in agreement with previous studies [7,9,36,40] showing that stress and other changes in environmental conditions, as well as the developmental stage of the plant can affect the expression level of transgenes and, in consequence, the characteristic targeted. Although the level of transgene expression was reduced in some transgenic lines upon transfer to greenhouse conditions, the transgene continued to be expressed in them when grown in field conditions.…”

“…Over such a long time period, transgenic trees will be subjected to both abiotic and biotic stresses. Since abiotic stresses such as heat and drought have been shown to reduce the activities of transgene expression in herbaceous species [7,9,36], and, in some cases, to result in gene silencing, another important question concerns the long-term stability of transgene expression in trees under conditions of stress.…”

Light-Regulated Transcription of Genes Encoding Peridinin Chlorophyll a Proteins and the Major Intrinsic Light-Harvesting Complex Proteins in the DinoflagellateAmphidinium carterae Hulburt (Dinophycae)1

“…Burn et al, 1993;Galaud, 1993) or transgenes (e.g. Meyer et al, 1992); for example, light-induced demethylation of distant regulatory sites correlated with increased levels of PEPCase mRNA levels in Zea mays (Langdale et al, 1991). However, we were unable to find precedents for methylation changes affecting endogenous genes involved in light harvesting.…”

Chromatin conversations: mechanisms and implications of paramutation

“…66). Indeed, in two instances paramutation is influenced by temperature: r1 paramutation in maize 67,68 and a1 transgene paramutation in Petunia 69 . The transfer of environmentally adapted expression states could be especially important for plants, the progeny of which are most often in the same location and similar environment as their parents.…”