Liposome model experiment for the study of assumed membrane damage in porphyria cutanea tarda

Chinese wild-growing Vitis amurensis ICE1 and ICE2 encode MYC-type bHLH transcription activators that regulate cold tolerance in Arabidopsis

Winter hardiness is an important trait for grapevine breeders and producers, so identification of the regulatory mechanisms involved in cold acclimation is of great potential value. The work presented here involves the identification of two grapevine ICE gene homologs, VaICE1 and VaICE2, from an extremely cold-tolerant accession of Chinese wild-growing Vitis amurnensis, which are phylogenetically related to other plant ICE1 genes. These two structurally different ICE proteins contain previously reported ICE-specific amino acid motifs, the bHLH-ZIP domain and the S-rich motif. Expression analysis revealed that VaICE1 is constitutively expressed but affected by cold stress, unlike VaICE2 that shows not such changed expression as a consequence of cold treatment. Both genes serve as transcription factors, potentiating the transactivation activities in yeasts and the corresponding proteins localized to the nucleus following transient expression in onion epidermal cells. Overexpression of either VaICE1 or VaICE2 in Arabidopsis increase freezing tolerance in nonacclimated plants. Moreover, we show that they result in multiple biochemical changes that were associated with cold acclimation: VaICE1/2-overexpressing plants had evaluated levels of proline, reduced contents of malondialdehyde (MDA) and decreased levels of electrolyte leakage. The expression of downstream cold responsive genes of CBF1, COR15A, and COR47 were significantly induced in Arabidopsis transgenically overexpressing VaICE1 or VaICE2 upon cold stress. VaICE2, but not VaICE1 overexpression induced KIN1 expression under cold-acclimation conditions. Our results suggest that VaICE1 and VaICE2 act as key regulators at an early step in the transcriptional cascade controlling freezing tolerance, and modulate the expression levels of various low-temperature associated genes involved in the C-repeat binding factor (CBF) pathway.

The role of possible membrane damage in porphyria cutanea tarda: a spin label study of rat liver cell membranes

Two groups of rats were made porphyric by treatment for a shorter or a longer time with hexachlorobenzene (HCB); a third group was subjected to chronic treatment with ethanol; the fourth group comprised untreated, control animals. Suspensions were prepared of hepatocytes isolated from the livers of the animals in the individual groups, and in these systems the cell membranes were studied by spin labeling. In all three chronically treated groups, the order parameter calculated from the ESR spectra was significantly lower than that of the control group. The order parameters ofr the first three treated groups, however, did not differ significantly from one another. If either HCB or ethanol was incorporated into the isolated hepatocytes of the healthy control animals, the fluidity of the hepatocyte membranes increased. The order parameter decrease (compared to the control) for the hepatocyte membranes of the animals treated chronically with HCB or ethanol can be ascribed to the direct membrane-fluidizing effect of HCB or ethanol, and also to the altered lipid metabolism. With regard to the difference in the mechanisms of action of HCB and ethanol, on the basis of the experimentally proved membrane-damaging effect of the porphyrinogenic HCB it is probable that, besides other factors, the membrane damage may play an important role in the pathogenesis of porphyria cutanea tarda.