Rossiter Henry Crozier 1943 - 2009

Ross Crozier, population geneticist and leader in the study of the evolutionary genetics of social insects, was born on 4 January 1943 in Jodhpur, India. He died of a heart attack in his office at James Cook University in Townsville on 12 November 2009. He is survived by his wife Yuen Ching Kok, who was his inseparable companion and collaborator in life as in the laboratory. Crozier was a pioneer in the application of molecular genetic markers to the analysis of social insect populations, and generated much of the theory that made these analyses possible. Ross and Ching Crozier produced the first sequence of the honey bee mitochondrial genome?the second insect mitochondria to be fully sequenced. From the sequence Crozier produced fundamental insights into the nature of DNA evolution, particularly directional mutation pressure towards particular nucleotides. Crozier contributed massively to the development of kin selection theory, which remains the most potent explanatory theory for the evolution of social behaviour in insects.

Insect mitochondrial genomics 2: the complete mitochondrial genome sequence of a giant stonefly, Pteronarcys princeps, asymmetric directional mutation bias, and conserved plecopteran A+T-region elements

Mitochondrial (mt) genome sequences of insects are receiving renewed attention in molecular phylogentic studies, studies of mt-genome rearrangement, and other unusual molecular phenomena, such as translational frameshifting. At present, the basal neopteran lineages are poorly represented by mt-genome sequences. Complete mt-genome sequences are available in the databases for only the Orthoptera and Blatteria; 9 orders are unrepresented. Here, we present the complete mt-genome sequence of a giant stonefly, Pteronarcys princeps (Plecoptera; Pteronarcyidae). The 16 004 bp genome is typical in its genome content, gene organisation, and nucleotide composition. The genome shows evidence of strand-specific mutational biases, correlated with the time between the initiation of leading and the initiation of lagging strand replication. Comparisons with other insects reveal that this trend is seen in other insect groups, but is not universally consistent among sampled mt-genomes. The A+T region is compared with that of 2 stoneflies in the family Peltoperlidae. Conserved stem-loop structures and sequence blocks are noted between these distantly related families.Key words: mitochondrial genomics, directional mutation pressure, A+T-rich region, Plecoptera, stonefly.

Codon usage and bias among individual genes of the coccidia and piroplasms

SummaryCodon usage has been analysed in individual gene sequences, derived from a variety of parasitic protozoa in the class Sporozoa of the phylum Apicomplexa using metric multidimensional scaling. The two groups of codon usage patterns detected reflect the two main subgroups of organisms studied (the coccidia and the piroplasms), and it is the pattern usage of synonymous codons that has the largest influence on overall codon usage in the individual genes, rather than being the pattern of amino acid composition of the gene product. The magnitude of the codon usage bias in the sequences was determined using three commonly used indices – NC', GC3sand B. In general, although relatively low levels of codon usage bias were detected in these gene sequences, codon usage bias does explain at least some of the codon usage patterns observed. Codon usage bias was observed to be dependent on the overall base composition of the genes analysed, which in turn was reflected in the types of codons that were either over-or under-represented in the nucleotide sequences. keeping with observations on prokaryotic organisms, it is speculated that the codon usage patterns detected in these parasitic protozoa are the result of directional mutation pressure on the base composition of the genomic DNA.