Plant phosphoglucose isomerase genes lack introns and are expressed in Escherichia coli

Nuclear genes that appear to encode both cytosolic and plastid isozymes of phosphoglucose isomerase (PGI), an essential glycolytic enzyme, have been isolated from three diploid species of the annual wild flower genus Clarkia (Onagraceae). The genes do not contain introns and are expressed to varying degrees in Escherichia coli when cloned in either Charon 35 phage or pUC plasmid vectors. The PGI proteins synthesized in E. coli form dimers, are catalytically active, and their electrophoretic mobilities are similar to those of appropriate Clarkia PGIs. The nucleotide sequence of a gene encoding a plastid isozyme of C. unguiculata is described.     

Ruptured fission yeast walls

Distributions of rupture sites of fission yeast cells ruptured by glass beads have been related to a new morphometric analysis. As shown previously (Johnson et al.,Cell Biophysics, 1995), ruptures were not randomly distributed nor was their distribution dictated by geometry, rather, ruptures at the extensile end were related to cell length just as the rate of extension is related to cell length. The extension patterns of early log, mid-log, late log, and stationary phase cells from suspension cultures were found to approximate the linear growth patterns of Kubitschek and Clay (1986). The median length of cells was found to decline through the log phase in an unbalanced manner.     

Allelic dimorphism in a surface antigen gene of the malaria parasite Plasmodium falciparum

Merozoites of the malaria parasite Plasmodium falciparum carry surface proteins processed from a precursor termed p190 or p195. Polymorphism has been reported in this protein. Since the protein is a candidate for a malaria vaccine, it is important to understand the nature of this polymorphism. We have determined the complete nucleotide sequence of the p190 gene from the MAD20 strain (a Papua New Guinea isolate). Comparisons of the gene with that from other strains of P. falciparum allowed us to study the genetic basis of the antigen's polymorphism. The gene consists of sequences distributed in variable blocks, which are separated by conserved or semi-conserved sequences. Variable sequences occur both in regions that code for tripeptide repeats and in regions with no apparent repeats. Interestingly, according to the present data, variable sequences are not widely polymorphic but fall into two distinct types. We argue that the p190 protein is encoded by dimorphic alleles capable of limited genetic exchange and present evidence at the nucleotide level documenting intragenic recombination in Plasmodium.     

Influence of muskmelon cell wall polysaccharides on roridin E production by a pathogenic strain of Myrothecium roridum

Addition of fruit cell wall extracts from two muskmelon cultivars into liquid media affected mycotoxin production by a strain of Myrothecium roridum pathogenic to muskmelon. Cell wall extracts from a susceptible cultivar (Iroquois) significantly increased toxin production while cell wall extracts from a resistant cultivar (Hales Best) significantly inhibited toxin production. Media containing 0.1 or 1.0 mg ml^–1 stimulated toxin production more than media containing 10 or 100 mg ml^–1 of cell wall extracts. Previous studies in our laboratory suggest that roridin E may be involved in virulence or pathogenicity of M. roridum; the present study indicates that cell wall polysaccharides as well as other materials present in cell wall preparations from susceptible host tissue provide a better substrate for toxin production than cell wall preparation from resistant host tissue.