Differential expression of a gene for a methionine-rich storage protein in maize

Summary A methionine-rich 10 kDa zein storage protein from maize was isolated and the sequence of the N-terminal 30 amino acids was determined. Based on the amino acid sequence, two mixed oligonucleotides were synthesized and used to probe a maize endosperm cDNA library. A fulllength cDNA clone encoding the 10 kDa zein was isolated by this procedure. The nucleotide sequence of the cDNA clone predicts a polypeptide of 129 amino acids, preceded by a signal peptide of 21 amino acids. The predicted polypeptide is unique in its extremely high content of methionine (22.5%). The maize inbred line BSSS-53, which has increased seed methionine due to overproduction of this protein, was compared to W23, a standard inbred line. Northern blot analysis showed that the relative RNA levels for the 10 kDa zein were enhanced in developing seeds of BSSS-53, providing a molecular basis for the overproduction of the protein. Southern blot analysis indicated that there are one or two 10 kDa zein genes in the maize genome.     

Transformation with a mutant Arabidopsis acetolactate synthase gene renders tobacco resistant to sulfonylurea herbicides

Summary A gene encoding acetolactate synthase was cloned from a chlorsulfuron-resistant mutant of Arabidopsis. The DNA sequence of the mutant gene differed from that of the wild type by a single base pair substitution. When introduced into tobacco by Ti plasmid-mediated transformation the gene conferred a high level of herbicide resistance. These results suggest that the cloned gene may confer agronomically useful levels of herbicide resistnace in other crop species, and that it may be useful as a selectable marker for plant transformation experiments.     

Human epithelial teratocarcinoma cells (P3): radiobiological characterization, DNA damage, and comparison with other rodent and human cell lines

Survival parameters and immediate DNA damage induced by 60Co gamma rays, 50-kVp X rays, and Janus fission-spectrum neutrons in human epithelial P3 cells (derived from an embryonic teratocarcinoma) are compared with those for Chinese hamster lung V79 cells. DNA damage caused by X and gamma irradiation, measured by alkaline elution methods, is the same in both cell types, whereas the P3 cells are about two times more sensitive (as measured by Do ratios of the final survival curve slope) to the lethal effects of these radiations than are the V79 cells. Human P3 cells are also more sensitive to the lethal effects of fission-spectrum neutrons than V79 cells. Survival experiments with split radiation doses and hypertonic salt treatment indicate that both P3 cells and V79 cells can recover from radiation-induced damage efficiently.     

Measurement of double-strand breaks in Chinese hamster cell DNA by neutral filter elution: calibration by 125I decay

We labeled the DNA of Chinese hamster lung V79 cells with 125I in the form of iododeoxyuridine and subsequently measured the elution of the DNA through polycarbonate filters at pH 9.6 and pH 7.2. Since decay of incorporated 125I produces predominantly double-strand breaks (DSB) in DNA at a rate close to one DSB per 125I decay, this measurement provides an absolute calibration for the assay of DSBs by neutral filter elution. Neutral elution profiles are not first order with respect to elution time; thus we have examined the relationships between accumulated 125I decays and several functions of retention of DNA on the filter at various times during the elution process. At both pH 9.6 and pH 7.2 there were linear relationships between accumulated decays and certain retention functions. The retention function most closely correlated to 125I decays for both pH values was the logarithm of the ratio of the retention of control DNA to that of 125I-labeled DNA, both evaluated at the 9th fraction (13.5 h of elution). The linear relationship between this ratio and 125I decays allows DSB induction to be determined directly from retention values. The calibration was used to measure DSBs induced by X rays.     

Short-term entrainment of ventilation to the walking cycle in humans

We describe a breath-by-breath method to test for entrainment of breathing and walking cycles. Thirty-eight normal subjects walked comfortably on a treadmill while breathing through a pneumotachograph. We analyzed the time intervals between heel strikes and the onset of inspiration (or expiration) for evidence of phase locking between steps and breaths, using Monte Carlo simulation to model the probability that n consecutive inspirations (or expirations) would begin at a constant time interval +/- 0.10 s from heel strikes by chance. We developed empirical criteria for rhythm synchronization during series of four or more breaths, while maintaining an estimated specificity of 95%. The majority of subjects showed some evidence of entrainment (29 +/- 23% of breaths on average), which occurred intermittently, usually lasting less than 10 breaths at a time. The precision of phase locking during spontaneous entrainment was similar to that in 10 subjects who attempted to maintain deliberate entrainment. The results suggest that the walking cadence provides a persuasive, but not dominant, input to the central breathing pattern generator. The present method can detect entrainment even when it occurs sporadically or with varying coupling pattern.     

Recovery of plants from leaf protoplasts of hybrid-poplar and aspen clones

Leaf protoplasts were isolated from shoot cultures of two hybrid poplar clones (Populus alba × P. grandidentata Crandon, NC-5339 and P. nigra Betulifolia × P. trichocarpa, NC-5331) and the Upright European Aspen (P. tremula Erecta) and were cultured in contact with screen discs floated in liquid medium. Protoplast culture was influenced by the growth medium of the source shoot cultures, the protoplast purification procedure, the plating density, and the presence or absence of a coconut water and casein hydrolysate supplement added to the culture medium. The protoplast-derived cells divided more quickly and with higher incidence than previously reported for hybrid poplars. Shoots were regenerated from the protoplast-derived calli and were maintained as shoot cultures. Plants were developed from microcuttings rooted ex vitro and were grown-on in the greenhouse and field.Abbreviations BA benzyladenine - NAA 1-naphthaleneacetic acid - TDZ thidiazuron - WPM Woody Plant Medium, Lloyd and McCown (1980) - MS Murashige and Skoog Medium (1962) - NC-XXXX North Central Forest Experiment Station accession number assigned to hybrid poplar clones.     

Ultra sensitive detection of Listeria monocytogenes in milk by the polymerase chain reaction (PCR)

The polymerase chain reaction (PCR) has been used to detect Listeria monocytogenes in whole milk at a level of 0.1 cfu per 30 ml. This high degree of sensitivity has been achieved following enzymatic digestion, polysulphonone membrane filtration and amplification of a nucleotide sequence within the promoter region of hlyA. Key elements of the procedure are the absence of enrichment culture and a complete solubilization of the membrane filter, ensuring total nucleic acid recovery. The simplicity of the protocol coupled with high sample volumes and exquisite sensitivity extends the relevance of PCR within food and environmental microbiology.     

Morphological dispersion of introduced Hawaiian finches: evidence for competition and a Narcissus effect

Summary Morphological analyses were conducted on finch species introduced to Oahu, Hawaii. As many as 25 species of finches representing four families (Emberizidae, Fringillidae, Ploecidae, Estrildidae) have been introduced to Oahu. Of these, 15 species currently have established wild populations. When compared with pools of 25 and 23 species introduced to Oahu, the 15 surviving species are morphologically overdispersed. This result is consistent with the hypothesis that competition has influenced the outcome of these introductions. We also tested the hypothesis that surviving introduced finches in one habitat (sugarcane fields) were morphologically overdispersed. When the seven surviving finch species found in sugarcane were compared with the pools of 25 and 23 species, they too were morphologically overdispersed. However, when the seven sugarcane species were compared with a species pool consisting of only the surviving 15 species found across Oahu, they were not morphologically overdispersed. This result suggests that morphological analyses of community structure based only on comparisons of assemblages of surviving species may be biased by a Narcissus effect.