The range of DNA sequences used to study the interrelationships of the major arthropod groups (chelicerates, myriapods, hexapods and crustaceans) is limited. Here we investigate the value of two genes not previously employed in arthropod phylogenetics. Histone H3 data were collected for 31 species and small nuclear ribonucleic acid U2 data for 29 species. The sequences provided a total of 460 sites and 192 parsimony-informative characters. H3 analyses showed substantial codon usage bias, but had a low consistency index (0.26). Consistency indices were higher for the U2 data (0.49), suggesting that the class of snRNAs may provide several phylogenetically useful genes. The present data are not by themselves sufficient to clarify major arthropod group relationships. Partitioned data for H3 and U2 are incongruent according to Incongruence Length Difference tests. Although the most parsimonious trees, based on combined analyses of all taxa, differ substantially from morphology-based trees, anomalous groupings are weakly supported with only one exception. The trees uphold monophyly of Onychophora, Branchiopoda, and Malacostraca (rather than the rival Phyllopoda). Cladistic analyses constraining the monophyly of morphologically defined classes do not significantly distinguish between the main rival hypotheses of major clade relationships. Combined (‘spliced’) analysis of both genes improves topological congruence with morphological groupings relative to that of either partition. Character congruence between H3, U2, and morphology is increased by downweighting (but not excluding) transitions and third codons. Analyses of four-taxon statements using PHYLTEST found significant support for the basal position of the Crustacea among the euarthropods. This support may be due to the similarity of chelicerates, myriapods and hexapods in percentage GC content.

Genetic maps were compiled from the analysis of 160–180 doubled haploid lines derived from 3 crosses: Cranbrook Halberd, CD87 Katepwa, and Sunco Tasman. The parental wheat lines covered a wide range of the germplasm used in Australian wheat breeding. The linkage maps were constructed with RFLP, AFLP, microsatellite markers, known genes, and proteins. The numbers of markers placed on each map were 902 for Cranbrook Halberd, 505 for CD87 Katepwa, and 355 for Sunco Tasman. Most of the expected linkage groups could be determined, but 10–20% of markers could not be assigned to a specific linkage group. Homologous chromosomes could be aligned between the populations described here and linkage groups reported in the literature, based around the RFLP, protein, and microsatellite markers. For most chromosomes, colinearity of markers was found for the maps reported here and those recorded on published physical maps of wheat. AFLP markers proved to be effective in filling gaps in the maps. In addition, it was found that many AFLP markers defined specific genetic loci in wheat across all 3 populations. The quality of the maps and the density of markers differs for each population. Some chromosomes, particularly D genome chromosomes, are poorly covered. There was also evidence of segregation distortion in some regions, and the distribution of recombination events was uneven, with substantial numbers of doubled haploid lines in each population displaying one or more parental chromosomes. These features will affect the reliability of the maps in localising loci controlling some traits, particularly complex quantitative traits and traits of low heritability. The parents used to develop the mapping populations were selected based on their quality characteristics and the maps provide a basis for the analysis of the genetic control of components of processing quality. However, the parents also differ in resistance to several important diseases, in a range of physiological traits, and in tolerance to some abiotic stresses.

During infection, pathogens must utilise the available nutrient sources in order to grow while simultaneously evading or tolerating the host’s defence systems. Amino acids are an important nutritional source for pathogenic fungi and can be assimilated from host proteins to provide both carbon and nitrogen. The hpdA gene of the dimorphic fungus Penicillium marneffei, which encodes an enzyme which catalyses the second step of tyrosine catabolism, was identified as up-regulated in pathogenic yeast cells. As well as enabling the fungus to acquire carbon and nitrogen, tyrosine is also a precursor in the formation of two types of protective melanin; DOPA melanin and pyomelanin. Chemical inhibition of HpdA in P. marneffei inhibits ex vivo yeast cell production suggesting that tyrosine is a key nutrient source during infectious growth. The genes required for tyrosine catabolism, including hpdA, are located in a gene cluster and the expression of these genes is induced in the presence of tyrosine. A gene (hmgR) encoding a Zn(II)2-Cys6 binuclear cluster transcription factor is present within the cluster and is required for tyrosine induced expression and repression in the presence of a preferred nitrogen source. AreA, the GATA-type transcription factor which regulates the global response to limiting nitrogen conditions negatively regulates expression of cluster genes in the absence of tyrosine and is required for nitrogen metabolite repression. Deletion of the tyrosine catabolic genes in the cluster affects growth on tyrosine as either a nitrogen or carbon source and affects pyomelanin, but not DOPA melanin, production. In contrast to other genes of the tyrosine catabolic cluster, deletion of hpdA results in no growth within macrophages. This suggests that the ability to catabolise tyrosine is not required for macrophage infection and that HpdA has an additional novel role to that of tyrosine catabolism and pyomelanin production during growth in host cells.

No abstract

The absence of expression of the granule-bound starch synthase I (GBSSI) allele from chromosome 4A of wheat is associated with improved starch quality for making Udon noodles. Several PCR-based methods for the analysis of GBSS alleles have been developed for application in wheat. A widely applied approach has involved a simple PCR followed by electrophoretic separation of DNA products on agarose gels. The PCR amplifies one band from each of the loci on chromosomes 4A (Wx-B1), 7A (Wx-A1), and 7D (Wx-D1), and the band from the Wx-B1 locus is diagnostic for the occurrence of the null Wx-B1 allele that is associated with improved starch quality. The reliable detection of the null Wx-B1 allele has been important in identifying wheat breeding lines. Allele-specific PCR has also been used to successfully detect the occurrence of the null Wx-B1 allele. In the present paper the various protocols were evaluated by testing a segregating double haploid population from a cross between Cranbrook and Halberd and the tests gave good agreement in different laboratories. The application of the DNAbased tests applied in wheat breeding programs provides one of the first examples of a molecular marker selection for a grain quality trait being successfully applied in an Australian wheat breeding program.

This study investigated the interspecific amplification of 35 microsatellite loci developed for M. alternifolia across seven other species within the Myrtaceae. All the primers used gave successful amplification of loci in at least one of the species tested. The level of success varied between species; 88.6% of primers gave amplification products for Melaleuca spp., 74.3% for Callistemon salignus, 45.7% for Eucalyptus spp. and 25.7% for Backhousia citriodora. Sequencing of a number of amplification products confirmed the presence of microsatellites in those loci. This study shows that the development of species-specific microsatellite libraries might not always be necessary. Cross-species amplification could enable the application of microsatellite technology to studies with limited resources, a feature characteristic of conservation projects.

Analysis of the microsatellite library by restriction digestion indicated that the sizes of clone inserts ranged from 130 to 1000 bp, with an average insert size of 415 bp. Of the 48 sequences analysed, dinucleotides were the most common microsatellite repeat type, with CA then GT occurring most frequently. Compound repeats consisting of 2 or 3 adjacent blocks of different dinucleotide repeats made up of 40% of the dinucleotide repeats. Eleven microsatellite clones of the 48 clones (23%) sequenced were suitable for primer design. Forty percent of inserts which contained microsatellite repeats were unusable because the repeats occurred too near the insert ends, thus leaving insufficient flanking sequence for primer design. Preliminary screening, which involved testing unlabelled primers on six hexaploid wheat cultivars, including Chinese Spring, showed that 6 of the 11 primers gave bands of the expected size on 3.5% agarose gels. The characteristics of the markers, including primer sequence, size of PCR product in reference cultivar, the number of repeat units and a description of the repeat motif are tabulated. Of the 6 primers fluorescently labelled, 5 primers, WMC 144, WMC 141, WMC136, WMC145 and WMC146, were used for subsequent microsatellite analysis. WMC144, WMC141 and WMC146 were polymorphic across the hexaploid wheat cultivars. The wild diploid accessions generally showed a high level of heterozygosity with WMC144 and WMC141, ranging from 60 to 100% in the 9 accessions of each Triticum monococcum, T. speltoides [Aegilops speltoides var. speltoides] and T. tauschii [Aegilops tauschii]. WMC144 amplified 2 alleles across all of the diploid accessions at 137 and 139 bp, which were common to the hexaploid cultivars. WMC141 amplified a wide range of allele sizes in both hexaploid and diploid genotypes. Additionally, the number of alleles observed with WMC141 was not consistent with the primer amplifying a single loci; that is, more than 2 products were amplified in diploids. Examples of this include T. monococcum (accession number 19848), which had an allele at 80, as well as showing heterozygotic alleles of 97 and 101 bp, and T. tauschii (accession number 24226) having alleles at 80 as well as 91 and 93 bp. Some of the fragments amplified by PCR using WMC136 on wild wheat progenitor and cultivated hexaploid wheat are shown in an electropherogram. Microsatellite loci were assigned to chromosomes corresponding to the aneuploid lines for which either no PCR amplification product was obtained, or one of the PCR products was missing, provided that all of the other aneuploid lines gave the relevant PCR product.

No abstract