fimA-folD genes linkage in Salmonella identifies a putative junctional site of chromosomal rearrangement in the enterobacterial genome

Abstract Analysis of the Salmonella chromosomal region located upstream of the fimA gene (coding for the major type 1 fimbrial subunit) showed a close linkage of this gene to the folD gene (coding for the enzyme 5,10-methylenetetrahydrofolate dehydrogenase/5, 10-methenyltetrahydrofolate cyclohydrolase), indicating that the fim gene cluster of Salmonella , unlike that of Escherichia coli , has no regulatory genes located upstream of fimA and apparently terminates with this gene. The respective locations of the fim and folD genes in the E. coli and Salmonella genetic maps suggests that the fimA-folD intergenic region of Salmonella encompasses a junctional site of a genetic rearrangement that probably originated from the different chromosomal location of the fim genes in these species.     

HAM: A new epitope-tag for in vivo protein labeling

The ability to metabolically label proteins with ³⁵S-methionine is critical for the analysis of protein synthesis and turnover. Despite the importance of this approach, however, efficient labeling of proteins in vivo is often limited by a low number of available methionine residues, or by deleterious side-effects associated with protein overexpression. To overcome these limitations, we have created a methionine-rich variant of the widely used HA tag, called HAM, for use with ectopically expressed proteins. Here we describe the development of a series of vectors, and corresponding antisera, for the expression and detection of HAM-tagged proteins in mammalian cells. We show that the HAM tag dramatically improves the sensitivity of ³⁵S-methionine labeling, and permits the analysis of Myc oncoprotein turnover even when HAM-tagged Myc is expressed at levels comparable to that of the endogenous protein. Because of the improved sensitivity provided by the HAM tag, the vectors and antisera described here should be useful for the analysis of protein synthesis and destruction at physiological levels of protein expression.     

Levels of genetic diversity at different stages of the domestication cycle of interior spruce in British Columbia

Concerns over the reductionist nature of the domestication of forest-tree species focus on the possibility of potential genetic erosion during this process. To address these concerns, genetic diversity assessments in a breeding zone the Province of British Columbia “interior” spruce (Picea glauca×engelmanni) program was conducted using allozyme markers. Genetic-variation comparisons were made between natural and production (seed orchard) populations as well as seed and seedling crops produced from the same breeding zone’s seed orchard. The natural population sample consisted of a total of 360 trees representing three stands within each of three watersheds present in the Shuswap-Adams low-elevation zone of interior British Columbia. Small amounts of genetic differentiation were observed among the nine natural populations (4%) and this was attributable to extensive gene flow Consequently, the sum of these nine populations was considered as a baseline for the genetic variation present in the breeding zone. The comparisons between the seed orchard and the breeding zone produced a similar percentage of polymorphic loci while the expected hetrozygosity (0.207 vs 0.210) and the average number of alleles per locus (2.7 vs 2.4) were slightly lower in the seed orchard. A total of seven natural populations’ rare alleles were not present in the orchard population, while one allele was unique to the orchard. The %P increased to 70.6% in the seedlot, but dropped to the natural populations level (64.7%) in the plantation. The observed increase in %P was a result of pollen contamination in the orchard. It is suspected that the reduction in the plantation was caused by an unintentional selection in the nursery. Simulated roguing in the orchard did not drastically reduce even if up to 50% of the orchard’s clones were rogued. However, roguing was associated with a reduction in the average number of alleles per locus (i.e., sampling effect). Received: 2 January 1996 / Accepted: 24 May 1996     

Fluorescent analysis of alpha-keto acids in serum and urine by high-performance liquid chromatography

A selective procedure using synthetic substrates for determination of exo-1,4,-beta-glucanases in a mixture of exoglucanases , endoglucanases , and beta-glucosidases is formulated. The heterobiosides , p- nithrophenyl -beta-D- cellobioside ( pNPC ) or p-nitrophenyl-beta-D-lactoside ( pNPL ), were used as selective substrates for the measurement of exoglucanase activity. The exoglucanases (especially cellobiohydrolases , which split off cellobiose units from the nonreducing end of the cellulose chain) specifically act on the agluconic bond (between p-nitrophenyl and the disaccharide moiety) and not on the holosidic bond (between the two glucose units of cellobiose). The interfering effect of beta-glucosidase, which acts on both agluconic and holosidic bonds, is overcome by the addition of D-glucono-1,5-delta-lactone, a specific inhibitor of beta-glucosidases. The interference of endoglucanases , which also act on both agluconic and holosidic bonds, can be compensated for by prior standardization of the assay procedure with a purified endoglucanase from the studied mixture of cellulases.     

Low mtDNA Cytb diversity and shallow population structure of Eleutheronema tetradactylum in the East China Sea and the South China Sea

Eleutheronema tetradactylum is an economically important fish species in China water. To investigate the genetic diversity and describe population structure of it, an 1151 base pair (bp) fragment of the mitochondrial DNA Cytb sequence was analyzed in 120 individuals from four populations in the East China Sea and the South China Sea. A total of 16 haplotypes were defined by 24 variable nucleotide sites. High level of haplotype diversity and low nucleotide diversity were observed in all populations. The results of AMOVA detected that 89.44% of the genetic variation occurred within populations. Significant genetic differentiations were detected among populations (0.05097, P < 0.05), but no large-scale regional differences were detected. Analysis of neutral evolution and mismatch distribution suggested no recent population expansion happened. The present results provided new information for genetic assessment, fishery management and conservation of this species.     

Tracking wind‐dispersed seeds using 15N‐isotope enrichment

Seed dispersal influences a wide range of ecological processes. However, measuring dispersal patterns, particularly long‐distance dispersal, has been a difficult task. Marking bird‐dispersed seeds with stable ¹⁵N isotopes has been shown to be a user‐friendly method to trace seed dispersal. In this study, we determined whether ¹⁵N urea solution could be used to enrich seeds of two common wind‐dispersed plants, Eupatorium glaucescens (Asteraceae) and Sericocarpus tortifolius (Asteraceae). We further tested if the water type (distilled versus tap) in ¹⁵N urea solutions influences the level and variability of enrichment of plant seeds, and if increasing spraying frequency per se increases enrichment. Because droughts may lower seed set or kill plants, we wanted to investigate if the additional use of an externally applied anti‐transpirant affects the intake of externally applied ¹⁵N into seeds. The results demonstrate that ¹⁵N enrichment of seeds can facilitate dispersal experiments with wind‐dispersed plants. The use of distilled water in ¹⁵N urea solutions did not increase ¹⁵N enrichment compared to tap water. Further, enrichment was more efficient at lower spray frequencies. Both the use of tap water and low frequencies could lower time, effort and project costs. The results suggest that species can be protected from drought using an anti‐transpirant without decreasing the incorporation of ¹⁵N into seeds.     

Minireview: Metabolic control of the reproductive physiology: Insights from genetic mouse models

This article is part of a Special Issue Energy Balance.