Localization of S-adenosylmethionine decarboxylase in murine tissues by immunohistochemistry

Comparative analysis of overexpressed Fragaria vesca S-adenosyl-l-methionine synthase (FvSAMS) and decarboxylase (FvSAMDC) during salt stress in transgenic Nicotiana benthamiana

We investigated the effect of overexpressing Fragaria vesca L. cv. Rügen S-adenosyl-l-methionine synthase (FvSAMS) and decarboxylase (FvSAMDC) genes on control and salt stressed Nicotiana benthamiana Domin plants. According to previous studies the overproduction of both proteins enhances the abiotic stress tolerance of plants, but the two enzymes have not yet been studied in one experimental system. We found that the transgenic plants subjected to long-term salt stress displayed higher levels of tolerance than the wild type (WT). In contrast to several earlier studies no antagonistic effect between ethylene and polyamine biosynthesis was observed in our experimental system. Overexpression of FvSAMDC had higher impact on the plant physiological parameters both in control and salt stress conditions, than that of FvSAMS. Based on the data measured in the FvSAMDC lines there appears to be a positive correlation between the free polyamine levels and the proline content as well as the amount of ethylene, while there is a negative correlation between the free polyamine levels and the lignin content in the plants exposed to salt stress. The transformation vectors contained the CaMV35S promoter, the coding sequence of FvSAMS and FvSAMDC fused with synthetic green fluorescent protein (sGFP). We detected the subcellular localization of both enzymes and examined the possible stress induced changes in their distribution. In the case of FvSAMS::sGFP nuclear, nucleolar, cytoplasmic (near to the plasmalemma), plastid membrane, whereas in FvSAMDC::sGFP nuclear and homogenous cytoplasmic localization was detected. Therefore, SAM is assumed to be produced in situ for numerous biochemical reactions.

Effects of chronically elevated growth hormone levels on polyamine metabolism in elderly transgenic mice

The polyamines are ubiquitous, multifunctional aliphatic amines with roles in cell growth, proliferation, differentiation, and malignant development. After growth stimulation, rapid and transient changes occur in polyamine regulatory enzymes. In this respect, acute effects of growth hormone (GH) injection on polyamine metabolic enzymes have earlier been shown. The present investigation comprises studies of the effects on polyamine metabolism of constitutively elevated levels of circulating GH in elderly transgenic (tg+) mice, overexpressing bovine GH. Polyamine levels were found to be constitutively altered in the liver and kidney of tg+ mice. Less changes were found in the spleen and none in the brain. The cellular uptake of polyamines in the liver from tg+ mice showed an increase and considerable changes were observed in the activity of ornithine decarboxylase (ODC) in the liver and kidney and S-adenosylmethionine decarboxylase (AdoMetDC) in the liver. A conspicuous finding was the distribution pattern of ODC protein in the liver and both tg- and tg+ animals. The results show that the effects of chronically elevated GH levels are organ-dependent and complex, and differ from acute GH effects. Despite high ODC activity and polyamine levels in liver, these mice did not display any malignant transformation even at an advanced age, indicating that high ODC activity is not sufficient to induce tumorigenesis in vivo.