Heavy metals both these trace elements necessary for life , as well as those niepełniące any physiological functions constitute a serious threat to human and animal health . Human activities has led to the emergence of huge amounts of these metals in soils around the world. Due to the high toxicity of heavy metals , there is an urgent need to develop more efficient and cheaper methods of soil remediation . Conventional methods of soil remediation are inefficient and expensive , and often result in the destruction of natural habitats .

Metallothioneins are low molecular weight, cysteine-rich, heavy-metal binding proteins. They are present in some Prokaryota, fungi, plants and animals. Attempts to isolate native plant proteins failed but many metallothionein genes were identified in mono- and dicotyledons and also in some gymno- sperms and algae. They are organised in small gene families, like in animals genomes and their expression is upregulated by different endo- and exogenous factors, including metal ions.

Genetic, biochemical and cytological studies on cytosine methylation in eukaryotic orga-nisms indicate intriguing links between DNA methylation, histone methylation, RNA interference and chroma- tin remodeling. It is clear that no single pathway accounts for all DNA methylations found in Eukaryota. In this article several general mechanisms which control methylation are briefly described.

In 1990s papers have been published suggesting the existence of an animal atrial natriuretic peptide (ANP) homologues in plant organisms. Multiple influence of egzogenic atrial natriuretic pepti- de into plant metabolism, growth and development has been showed. Plant ANP immunohomologues has been studied as well. However, the plant nucleotide or aminoacid sequence similar to the animal NP have not yet been published. The existence of plant NP homologues to the animal natriuretic pepti- des and genes encoding them was not established.