Metabolic Changes in Excised Fruit Tissue. IV. Changes Occurring in Discs of Apple Peel During the Development of the Respiration Climacteric

It is shown that a sequential development of a series of enzyme systems occurs in the peel of the apple as the respiration climacteric develops in the whole fruit. The sequence of development of these systems, i.e. acetate incorporation into lipid, production of ethylene, incorporation of amino acid into protein and, finally, the decarboxylation of added malate (malate effect) is the same as that shown earlier for the short term (24 hr) aging of peel discs from pre-climacteric apples. As these systems appear in the initial discs from fruit passing through the climacteric they gradually cease to increase during the 24 hour aging period. Uptake studies show that none of the changes in these systems can be due solely to changes in the permeability of the tissue over the climacteric period. On the basis of these results it is tentatively suggested that the aging of discs from pre-climacteric tissue might provide a model system for a detailed study of the physiological and biochemical changes occurring during the climacteric of apple fruits.     

Mutation analysis of the cystic fibrosis transmembrane regulator gene in native American populations of the southwest

We report DNA and clinical analyses of cystic fibrosis (CF) in two previously unstudied, genetically isolated populations: Pueblo and Navajo Native Americans. Direct mutation analysis of six mutations of the CFTR gene--namely, delta F508, G542X, G551D, R553X, N1303K, and W1282X--was performed on PCR-amplified genomic DNA extracted from blood samples. Haplotype analyses with marker/enzyme pairs XV2c/TaqI and KM19/PstI were performed as well. Of the 12 affected individuals studied, no delta F508 mutation was detected; only one G542X mutation was found. None of the other mutations was detected. All affected individuals have either an AA, AC, or CC haplotype, except for the one carrying the G542X mutation, who has the haplotype AB. Clinically, six of the affected individuals examined exhibit growth deficiency, and five (all from the Zuni Pueblo) have a severe CF phenotype. Four of the six Zunis with CF are also microcephalic, a finding not previously noted in CF patients. Our DNA data have serious implications for risk assessment of CF carrier status for these people.     

A yeast-Escherichia coli shuttle vector containing the M13 origin of replication

A yeast-Escherichia coli shuttle vector containing the M13 origin of replication has been constructed. This vector allows selection and replication in both Saccharomyces cerevisiae and E. coli, as well as single-stranded packaging from E. coli upon infection with a helper phage. The presence of a polylinker with various unique restriction sites facilitates the cloning of desired genes.     

Genetic Analysis of Hispanic Individuals with Cystic Fibrosis

We have performed molecular genetic analyses of Hispanic individuals with cystic fibrosis (CF) in the southwestern United States. Of 129 CF chromosomes analyzed, only 46% (59/129) carry ΔF508. The G542X mutation was found on 5% (7/129) of CF chromosomes. The 3849+10kbC→T mutation, detected primarily in Ashkenazi Jews, was present on 2% (3/129). R1162X and R334W, mutations identified in Spain and Italy, each occurred on 1.6% (2/129) of CF chromosomes. W1282X and R553X were each detected once. G551D and N1303K were not found. Overall, screening for 22 or more mutations resulted in detection of only 58% of CF transmembrane conductance regulator gene mutations among Hispanic individuals. Analysis of KM19/XV2c haplotypes revealed an unusual distribution. Although the majority of ΔF508 mutations are on chromosomes of B haplotypes, the other CF mutations are on A and C haplotypes at higher-than-expected frequencies. These genetic analyses demonstrate significant differences between Hispanic individuals with CF and those of the general North American population. Assessment of carrier/affected risk in Hispanic CF individuals cannot, therefore, be based on the mutation frequencies found through studies of the general population but must be adjusted to better reflect the genetic makeup of this ethnic group. Further studies are necessary to identify the causative mutation(s) in this population and to better delineate genotype/phenotype correlations. These will enable counselors to provide more accurate genetic counseling.     

Low codon bias and high rates of synonymous substitution in Drosophila hydei and D. melanogaster histone genes

We have evaluated codon usage bias in Drosophila histone genes and have obtained the nucleotide sequence of a 5,161-bp D. hydei histone gene repeat unit. This repeat contains genes for all five histone proteins (H1, H2a, H2b, H3, and H4) and differs from the previously reported one by a second EcoRI site. These D. hydei repeats have been aligned to each other and to the 5.0-kb (i.e., long) and 4.8-kb (i.e., short) histone repeat types from D. melanogaster. In each species, base composition at synonymous sites is similar to the average genomic composition and approaches that in the small intergenic spacers of the histone gene repeats. Accumulation of synonymous changes at synonymous sites after the species diverged is quite high. Both of these features are consistent with the relatively low codon usage bias observed in these genes when compared with other Drosophila genes. Thus, the generalization that abundantly expressed genes in Drosophila have high codon bias and low rates of silent substitution does not hold for the histone genes.      

Growth and monoterpene production by transformed shoot cultures of Mentha citrata and Mentha piperita in flasks and fermenters

This paper reports studies on the growth and biosynthesis of monoterpenes by transformed shoot cultures of Mentha citrata and Mentha piperita, originally developed 5 years ago and since maintained by regular subculturing. Throughout this time, the M. citrata culture has stably maintained production of an oil closely resembling that of the parent plant in which linalool and linalyl acetate are the predominant components. However, M. piperita, which initially showed a divergence from the parent plant in producing significant amounts of menthofuran in addition to the characteristic oil components menthol and menthone, has now been found to produce pulegone and menthofuran as the major components. The cultures were subjected to different environmental conditions of varying periods of light and temperature in an attempt to restore menthol and menthone production. Increased illumination reduced the yields of pulegone and menthofuran but did not stimulate the production of either menthol or menthone, which remained only at trace levels (below 0.2 g/g fresh weight). Cultures of M. citrata were, however, stimulated by increased illumination, and produced more linalool and linalyl acetate. Shoot cultures of M. citrata and M. piperita were grown in 14–1 fermenters for up to 60 dys during which the biomass increased from approximately 100 g to 2.5 kg and 3.5 kg respectively. Both cultures rapidly consumed sucrose with a concomitant release of glucose, and the uptake of inorganic ions was similar except that M. citrata consumed far less Na+ during the fermentation. The total yields of monoterpenes from the fermentations were 1.16 g (M. piperita) and 0.18 g (M. citrata). *** DIRECT SUPPORT *** AG903062 00005