Genes active in developing wheat endosperm.

This paper describes the construction and characterisation of a cDNA library from wheat endosperm tissue during the early stages of grain filling. Developing wheat endosperm tissue was characterised with respect to standard measures including dry weight, cytological appearance and timing of expression of major sources of mRNA such as the seed storage protein genes. In addition, the full complement of proteins present at mid-endosperm development was examined using 2D-electrophoretic techniques. Based on this characterisation, endosperm from the developing grain 8-12 days post-anthesis was chosen for isolating mRNA and preparing cDNA. At this stage in development the mRNA population is not yet dominated by the accumulation of mRNA from seed storage protein genes. A cDNA library, not normalised, containing a high percentage of full length cDNA clones was constructed and 4,319 clones sequenced ("single-pass"). Partitioning of the cDNA sequences into gene families and singletons provided the basis for quantifying the accumulation of sequence classes relative to the total number of sequences determined. The accumulation of gene families/singletons was not linear. However, mathematical modeling of the data suggested that the maximum number of different genes expressed is within the range of 4,500-8,000 (detailed in the Appendix). If an average is taken of these extremes, approximately 27% of the gene products were visible as proteins in the 2D-electrophoretic analysis. Analysis of a functional class of genes relevant to wheat grain end-use, namely the glutenin/gliadin seed storage protein class of genes, revealed a new category of gene characterised by a distinctive N-terminal domain and a reduced central repetitive domain.

A transient assay for evaluating promoters in wheat endosperm tissue.

A transient assay was developed for the evaluation of promoter sequences in wheat endosperm tissue. A deletion series from an omega-secalin gene promoter, located on chromosome 1RS.1DL of specific wheat lines, were translationally fused to a uidA reporter gene. These promoters were evaluated for expression in wheat endosperm tissue after integration of the DNA into the cell using microprojectile bombardment. The results were compared with those obtained using other transient assay systems.

The Sec-1 locus on the short arm of chromosome 1R of rye (Secale cereale).

This paper describes a detailed sequence analysis of the omega-secalin gene array at the Sec-1 locus on the short arm of chromosome 1 of rye. The analysis shows that the genes are separated by 8 kb of spacer sequence and that the gene/spacer units are arranged in a head to tail fashion. The boundaries of the array are identified, and a fragment containing the majority of the genes in the array is separated by PFG analysis. The sequence data of one 9.2 kb gene unit have been determined, and because of the similarity of the gene units within the array these data provide a detailed sequence analysis of 140 kb of the Sec-1 locus. Fluorescence in situ hybridization, using lambda clones isolated for the structural analysis, identifies the position of the array on the rye chromosomes relative to the 5S rRNA genes.

Changing the hours of shiftwork: a comparison of 8- and 12-hour shift rosters in a group of computer operators.

Twelve-hour shifts are currently regarded by many workers as one solution to the disruptive effects of shiftwork on health, well-being and lifestyle. Twelve-hour shifts offer larger and more frequent blocks of leisure time than do 8-h shifts. Nevertheless, concern must be addressed about the possible effects of working these additional hours on work quality and productivity and whether they are worked at significant extra cost to the worker. In a study of 75 computer operators, the effect of changing from a predominantly 8 h per shift irregular roster to a 12 h per shift regular roster was investigated. Operators completed a questionnaire covering demographic and health details including the General Health Questionnaire (GHQ), and details about general job satisfaction including the Work Environment Scale (WES). They also completed a 14-day diary of sleeping and eating patterns and mood state at the beginning and end of each shift for the same period. The questionnaires and diaries were completed first under the 8-h shift roster, then again 12 months later after the 12-h shift roster had been worked for 7 months. Work quality, productivity, staff turnover and sickness and other absence data were also collected under the two shift systems. The results showed that changing to the 12-h shift roster produced improvements in health, particularly in psychological health and in reduced feelings of tiredness throughout the work period. The change in working hours was at no cost to feelings of job satisfaction or the worker's perceptions of any particular aspects of the work environment, or to measures of productivity.

A model of quantitative traits under frequency-dependent balancing selection.

We describe a computer model that stimulates a combination of stabilizing and frequency-dependent selection acting on a quantitative character determined by several loci. The results correspond to many features of natural variations at both the phenotypic and genotypic levels. The model is robust, and its results are not strongly dependent either on the nature and shape of the function describing the stabilizing selection, or on the precise form of frequency dependence, except near the extrema. It suggests a mechanism for the maintenance of large amounts of variability, and shows a relation between population size and heterozygosity roughly corresponding to that found in nature. In this respect it is unlike the purely neutral model.

Mutational order: a major stochastic process in evolution.

Computer simulations in which selection acts on a quantitative character show that the randomness of mutations can contribute significantly to evolutionary divergence between populations. In different populations, different advantageous mutations occur, and are selected to fixation, so that the populations diverge even when they are initially identical, and are subject to identical selection. This stochastic process is distinct from random genetic drift. In some circumstances (large populations or strong selection, or both) mutational order can be greatly more important than random drift in bringing about divergence. It can generate a 'disconnection' between evolution at the phenotypic and genotypic levels, and can give rise to a rough 'molecular clock', albeit episodic, that is driven by selection. In the absence of selection, mutational order has little or no effect.

Phylogenetic relationships of Triticum tauschii, the D-genome donor to hexaploid wheat. 4. Variation and chromosomal location of 5S DNA.

The 5S DNA sequences in Triticum tauschii are organised in large clusters containing units that are primarily either 420 ("short") or 490 base pairs (bp) in length ("long"). The main cluster of short units was shown to be located on chromosome 1D in hexaploid wheat and is designated 5SDna-D1, while the cluster of long units was shown to be on chromosome 5D and is designated 5SDna-D2. The chromosomal locations in hexaploid wheat most likely correspond to those in T. tauschii and this could be shown directly for the 5SDna-D2 locus by using a T. tauschii 5D substitution in 'Chinese Spring' wheat. The sequence alignment of units derived from 5SDna-D1 and 5SDna-D2 revealed three apparent deletions in the noncoding spacer region, which were fixed in units from 5SDna-D1, and one deletion, which was fixed in units from 5SDna-D2. A minor size class, 400 bp long and closely related to the units from 5SDna-D1, was found in 2 of 415 accessions surveyed. A continuous range of quantitative changes in the number of 5S DNA units at the two loci was evident with up to a 10-fold relative abundance level of units being found in some accessions. Triticum tauschii var. typica was particularly noteworthy in that many accessions showed more units at 5SDna-D2 relative to 5SDna-D1. Partial thermal dissociation experiments with radioactive probes, synthesized from either the short or long 5S DNA units, hybridized to genomic DNA showed that the population of units at the respective loci were relatively homogeneous and clearly distinct from each other.(ABSTRACT TRUNCATED AT 250 WORDS)

The molecular-cytogenetic analysis of grasses and its application to studying relationships among species of the Triticeae.

An analysis of four species from the genus Secale, including the study of different accessions, has shown that the properties of DNA clones of monomer units from three repeated sequence loci, namely, Ter, Nor, and 5S DNA, proved to be representative of the entire loci from which they were isolated. This finding in Secale species, including the discovery of a new locus for 5S DNA on chromosome 5R, has been used to interpret information on the Ter, Nor, and 5S DNA loci from 15 species in the Triticeae complex. The evolutionary relationship among species suggested by the DNA sequence data has shown many consistencies with a number of other characters such as those used in classical systematics, as well as geographical distribution data and isozyme and chromosome-pairing studies. Apparent inconsistencies such as a close relationship between the R and P genomes at the Ter loci are interpreted in terms of amplification-deletion phenomena known to occur at repetitive sequence loci. In addition, this study included species endemic to Australia and thus provided a broad time span in which to consider some features of repeated sequence family evolution, such as the conservation of certain parts of 5S DNA spacer regions.

Frequency-dependent selection, metrical characters and molecular evolution.

Computer models of selection acting on a quantitative character show that a combination of frequency-dependent and stabilizing selection can maintain many polymorphisms among the genes that determine the character. The models also show that the random order of mutations can give rise to selectively driven stochastic effects that are sometimes more important than random genetic drift. They suggest simple explanations for patterns of divergence between populations and species, and for apparent discrepancies between the rates of morphological and molecular evolution. They point towards a selective theory of 'molecular clocks'.

The clinico-pathology of a malignant catarrhal fever syndrome in the Indonesian swamp buffalo (Bubalus bubalis).

Between September 1979 and May 1982, 50 of 177 swamp buffaloes became sick and died 83 to 719 days (mean 271) after being transferred to a research facility and housed in quarters adjacent to where sheep and goats were kept. The major clinical signs were anorexia, fever, conjunctivitis, scleral hyperaemia, ocular discharge, hyperaemia of skin, enlargement of lymph nodes and depression. Postmortem and histopathological lesions were observed in most of the tissues and organs of the body. A vasculitis with adventitial mononuclear cell infiltration and lymphoreticular reactions suggested a relationship to malignant catarrhal fever. The occurrence of serofibrinous epicarditis and myocarditis, which was seen in buffaloes in all cases, has not been a common finding in ruminants with malignant catarrhal fever.

Transmission and virological studies of a malignant catarrhal fever syndrome in the Indonesian swamp buffalo (Bubalus bubalis).

A malignant catarrhal fever-like syndrome in indonesian swamp buffalo was experimentally transmitted to one of 2 Bos indicus and 3 of 3 Bos javanicus cattle by intravenous inoculation of 250 ml of citrated, whole blood from affected buffaloes. The 4 cattle developed clinical signs of disease on average 32.5 days after receiving the inoculation of blood. The 4 cattle died after a variable period of illness. None of a further 3 B. javanicus cattle inoculated intravenously with a spleen homogenate prepared from another affected buffalo developed the disease. The experimental disease was clinically and pathologically similar to the natural disease in buffaloes although differences were noted. Attempts to adapt the agent to mice, guinea pigs and rabbits failed. A cytopathic agent (Japanese encephalitis virus) was isolated from the spleen of one buffalo with clinical signs but was not considered significant. Sixty-three B. indicus, 7 B. javanicus (and 6 of their crosses), 3 B. taurus and 4 Bubalus bubalis (Murrah buffalo) were kept in the same quarters where 50 of 177 swamp buffaloes died between September 1979 and May 1982. Four of the 7 B. javanicus cattle developed the clinical signs of disease and died. All the other cattle in contact remained healthy.

The evolution of genetic diversity.

The existence within natural populations of large amounts of genetic variation in molecules and morphology presents an evolutionary problem. The 'neutralist' solution to this problem, that the variation is usually unimportant to the organism displaying it, has now lost much of its strength. Interpretations that assume widespread heterozygous advantage also face serious difficulties. A resolution is possible in terms of frequency-dependent selection by predators, parasites and competitors. The evidence for pervasive frequency-dependent selection is now very strong. It appears to follow naturally from the behaviour of predators, from the evolutionary lability of parasites, from the ecology of competition and, at the molecular level, from the phenomena of enzyme kinetics. Such selection can explain the maintenance not only of conventional polymorphism but also of continuous variation in both molecular and morphological characters. It can account for the occurrence of diversity within groups of haploid and self-fertilizing organisms, and for the evolution of differences between individuals in their systems of genetic control.