SEM observations on polar body elimination and changes of the oocyte surface during egg maturation in the newt Triturus alpestris (Amphibia,Urodela)

Summary We have studied the surface of the animal half of ovulated newt eggs recovered from different portions of the oviduct. The germinative area, about 40 m diameter, is localized in the region of the whitish polar spot, about 450 m diameter. The structural changes in the germinative area are connected with the formation and extrusion of the first and second polar bodies. Of the two types of oviductal eggs observed, those covered with microvilli (type 1) were found only in the ostial portions of the oviduct, whilst those covered with microfolds (type 11) were found more distally. The structural difference between these two types may be related to the known reduction in surface area of the cell membrane during oocyte maturation. Offprint requests to: W. Kilarski     

Effect of DNA gyrase inhibitors on gene expression of the cysteine regulon

Summary Nalidixic acid inhibits the expression of those cysteine genes which are regulated by the cysB product, it has no affect, however, on the constitutively expressed cysE gene. The expression of cysteine genes in a strain carrying a mutation in the nalA locus is resistant to this drug. Novobiocin affects the expression of cysteine genes similarly to nalidixic acid. The effect of nalidixic acid on the expression of genes in a cysteine constitutive mutant was studied.     

RAPD analysis of the interspecific somatic hybrids: Solanum bulbocastanum (+) S. tuberosum

The diploid Mexican species S. bulbocastanum (blb) was used as a source of late blight resistance in somatic hybridization with the potato (S. tuberosum, tbr) dihaploid H-8105. The produced 2x blb (+) 2x tbr H-8105 somatic hybrids did not retain the blb parent's characteristic high resistance to P. infestans. The revealed aneuploidy of blb (+) tbr H-8105 hybrids indicated a possible loss of individual blb chromosome(s) carrying the resistance genes. Four hybrid clones differing in terms of their ploidy, morphology and growth potential were analysed for the presence of all twelve blb chromosomes (linkage groups). The RAPD markers assigned to particular chromosomes were selected on the basis of the linkage map of S. bulbocastanum constructed by Naess et al., Mol. Gen. Genom. 265 (2001) 694-704. Of the 86 markers analysed, twelve (14%) were common for blb and H-8105, while 34 (40%) and 40 (46%) markers were specific for the blb and H-8105 genome, respectively; this confirms the differences between the nuclear genomes of the two species. Seventeen markers (20%) present in one or the other parent were absent in the hybrids, and only one new marker was found in the hybrids. The poorly growing, aneuploid and chimeric hybrids had the same band profiles as the well growing, morphologically normal hybrids, except for two bands that were present only in normal hybrids. The presence of eleven blb linkage groups in the blb (+) tbr H-8105 hybrids was confirmed. The markers specific for the second linkage group (chromosome 2) of blb were not present in the RAPD patterns of the somatic hybrids analysed, suggesting a loss or rearrangement of this chromosome in the combined nuclear genome of the hybrids.     

Synthesis and Biological Activity of a Bis-Substituted 3′-Deoxyadenosine Analog of 2–5A

Abstract

The 5′-monophosphate, p5′(3′dA)2′p5′A2′5′(3′dA), was synthesized and found to bind to the 2–5A-dependent endonuclease of mouse L cells only two-three times less effectively than the parent p5′A2′p5′A2′p5′A. When evaluated for its ability to activate the 2–5A-dependent endonuclease, ppp5′(3′dA)2′p5′A2′p5′(3′dA) was found to be fifty times more effective than ppp5′A2′p5′(3′dA)2′p5′A and ten times less effective than 2–5A as an endonuclease activator     

Expression of HvHMA2 in tobacco modifies Zn–Fe–Cd homeostasis

HvHMA2 is a plasma membrane P_1B-ATPase from barley that functions in Zn/Cd root-to-shoot transport. To assess the usefulness of HvHMA2 for modifying the metal content in aerial plant parts, it was expressed in tobacco under the CaMV35S promoter. Transformation with HvHMA2 did not produce one unique pattern of Zn and Cd accumulation; instead it depended on external metal supply. Thus Zn and Cd root-to-shoot translocation was facilitated, but not at all applied Zn/Cd concentrations. Metal uptake was restricted in HvHMA2-transformed plants and the level in the shoot was not enhanced. It was shown that HvHMA2 localizes to the plasma membrane of tobacco cells, and overloads the apoplast with Zn, which could explain the overall decrease in metal uptake observed. Despite the lower levels in the shoot, HvHMA2 transformants showed increased Zn sensitivity. Moreover, introduction of HvHMA2 into tobacco interfered with Fe metabolism and Fe accumulation was modified in HvHMA2-transformants in a Zn- and Cd-concentration dependent manner. The results indicate that ectopic expression of the export protein HvHMA2 in tobacco interferes with tobacco metal Zn–Cd–Fe cross-homeostasis, inducing internal mechanisms regulating metal uptake and tolerance.