Philip A. O’Brien

Bio: Philip A. O’Brien is an academic researcher from Murdoch University. The author has contributed to research in topics: Phytophthora cinnamomi & Rhizoctonia solani. The author has an hindex of 23, co-authored 76 publications receiving 1904 citations. Previous affiliations of Philip A. O’Brien include University of Western Australia.

Myostatin and its implications on animal breeding: a review

Abstract: Myostatin, or growth and differentiation factor 8 (GDF8), has been identified as the factor causing a phenotype known as double muscling, in which a series of mutations render the gene inactive, and therefore, unable to regulate muscle fibre deposition. This phenotype occurs at a high frequency in some breeds of cattle such as Belgian Blue and Peidmontese. Phylogenetic analysis has shown that there has been positive selection pressure for non-synonymous mutations within the myostatin gene family, around the time of the divergence of cattle, sheep and goats, and these positive selective pressures on non-ancestral myostatin are relatively recent. To date, there have been reports of nine mutations in coding regions of myostatin that cause non-synonymous changes, of which three cause missense mutations. including two in exon 1 and one in exon 2. The remaining six mutations, located in exons 2 and 3, result in premature stop codons, which are the mutations responsible for the double-muscling phenotype. Unfortunately, breed management problems exist for double-muscled cattle, such as birthing difficulties, which can be overcome through genetically controlled breeding programmes, as shown in this review.

Molecular Characterization of Cryptosporidium Isolates From Humans and Other Animals Using Random Amplified Polymorphic Dna Analysis

Abstract: Genetic variation in 25 Cryptosporidium isolates was analyzed using the random amplified polymorphic DNA (RAPD) technique. Simple reproducible polymorphisms were generated (using five primers) from Cryptosporidium DNA that was free of contaminating bacterial DNA. The results generated by four of the five primers were statistically correlated (P < 0.001). The combined data from three primers were used to construct a phenogram using Jaccard's distance. Four groupings could be distinguished. Two C. serpentis isolates from snakes formed a distinct group of their own, whereas C. parvum isolates were divided into two main groups: one containing most human isolates and the other containing mostly domestic animals plus two remaining human isolates. Due to the sensitivity of the RAPD technique, isolates can now be analyzed genetically, directly from fecal samples without further biological amplification. This represents a significant advance on current techniques.

Phosphite primed defence responses and enhanced expression of defence genes in Arabidopsis thaliana infected with Phytophthora cinnamomi

Abstract: This paper describes the effect of phosphite (Phi), a systemic chemical, on the induction of defence responses in Phytophthora cinnamomi-infected Arabidopsis thaliana accessions Ler and Col-0. Application of Phi to non-inoculated A. thaliana seedlings of accession Ler elevated transcription of defence genes in the salicylic acid (PR1 and PR5) and jasmonic acid/ethylene (THI2.1 and PDF1.2) pathways. Furthermore, a systemic increase in the expression of the PR1 gene was demonstrated in Phi-treated seedlings using the transgenic line PR1::GUS in the presence/absence of the pathogen by 72h after inoculation. The cells of Phi-treated A. thaliana Ler leaves responded to P. cinnamomi zoospore inoculation with a rapid increase in callose deposition and hydrogen peroxide (H2O2) production. Phi treatment resulted in the production of callose papillae 6h earlier than in non-Phi-treated inoculated seedlings and enhanced the production of H2O2 in the leaves of A. thaliana at the site of hyphal penetration and in cells away from the inoculation point. By 24h after infection, clear differences in the amount of H2O2 production were observed between the Phi-treated and non-Phi-treated plants. These rapid host responses did not occur in non-Phi-treated inoculated seedlings. There was also a significant (P<0·001) decrease in lesion size in Phi-treated plants. These results indicate that Phi primes the plant for a rapid and intense response to infection involving heightened activation of a range of defence responses.

Three Clonal Lineages of Phytophthora cinnamomi in Australia Revealed by Microsatellites.

Abstract: The genetic structure of populations of Phytophthora cinnamomi, a pathogen of an enormous variety of woody plants, was investigated using microsatellites. Three intensively sampled disease sites in southwest Australia were analyzed along with a large culture collection of Austra-lian isolates and some isolates from elsewhere in the world. The mutation in the four microsatellite loci analyzed revealed spatial patterns at the disease sites that correlated with the age of the infestation. Only three clonal lineages were identified in Australian populations and these same clonal lineages were present in worldwide populations, where it is suggested that a limited number of clonal lineages have spread in most regions. No evidence for sexual reproduction between these clonal lineages in Australia has been found even though the pathogen has the opportunity. Instead, mitotic recombination is frequent within the clonal lineages. The implications of this are discussed.

Microsatellites for ecologists: a practical guide to using and evaluating microsatellite markers

Abstract: Recent improvements in genetic analysis and genotyping methods have resulted in a rapid expansion of the power of molecular markers to address ecological questions. Microsatellites have emerged as the most popular and versatile marker type for ecological applications. The rise of commercial services that can isolate microsatellites for new study species and genotype samples at reasonable prices presents ecologists with the unprecedented ability to employ genetic approaches without heavy investment in specialized equipment. Nevertheless, the lack of accessible, synthesized information on the practicalities and pitfalls of using genetic tools impedes ecologists ability to make informed decisions on using molecular approaches and creates the risk that some will use microsatellites without understanding the steps needed to evaluate the quality of a genetic data set. The first goal of this synthesis is to provide an overview of the strengths and limitations of microsatellite markers and the risks, cost and time requirements of isolating and using microsatellites with the aid of commercial services. The second goal is to encourage the use and consistent reporting of thorough marker screening to ensure high quality data. To that end, we present a multistep screening process to evaluate candidate loci for inclusion in a genetic study that is broadly targeted to both novice and experienced geneticists alike.

Mapping genes for complex traits in domestic animals and their use in breeding programmes

Abstract: Genome-wide panels of SNPs have recently been used in domestic animal species to map and identify genes for many traits and to select genetically desirable livestock. This has led to the discovery of the causal genes and mutations for several single-gene traits but not for complex traits. However, the genetic merit of animals can still be estimated by genomic selection, which uses genome-wide SNP panels as markers and statistical methods that capture the effects of large numbers of SNPs simultaneously. This approach is expected to double the rate of genetic improvement per year in many livestock systems.