SPEAKER: Professor Arthur Georges, Institute for Applied Ecology, University of Canberra, ACT

DATE: Friday, 29th July 2016
LOCATION: Geelong Campus at Waurn Ponds, Room KA4.207
TIME: 1:30pm
Seminar will also be video linked to the following campuses: Melbourne Campus at Burwood, Burwood Corporate Centre (BCC) and Warrnambool Campus, Room J2.22

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ABSTRACT: Although phenotype is governed by underlying genotype, the translation of the genetic blueprint to traits possessed by the individual is under varying degrees of environmental influence, leading to phenotypic variation in traits with a common genetic underpinning.

Sex of an individual, at least in vertebrates, was once thought to be strictly determined by the complement of chromosomes passed to the offspring from the parents. The prevailing view of a 1:1 correspondence between genotype and sexual phenotype (genetic sex determination or GSD) that is so prevalent in mammals and birds, fell away with the discovery of astonishing diversity in the mechanisms of sex determination of many lineages of reptile and fish.

Environmental sex determination is now well established in these groups, and temperature early in development is the primary factor involved (hence, temperature-dependent sex determination, or TSD). Indeed, sex determination in reptiles is seen as one of the most profound examples of developmental plasticity among vertebrates.

Furthermore, it falls in a special class of phenotypic plasticity, along with castes in bees and winged/winglessness in aphids – a polyphenism with two states, whereby intermediate forms are either not viable or with severely compromised fitness.

In this presentation, the focus will be on a special case of sex determination where genotype and environment interact to determine sex, and discuss the mechanisms by which temperature may bring influence.

The dragon lizard, Pogona vitticeps, has well defined sex chromosomes – a ZZ/ZW system as in birds – yet temperature can over-ride the genetic signal to reverse the ZZ male trajectory to a female phenotype, both in the laboratory and in the wild.

This is one example where developmental plasticity can drive rapid evolutionary responses to changing climate, responses that challenge our understanding of the evolution of temperature-dependent sex determination.

BIO: Professor Arthur Georges is an ecologist and herpetologist whose research interests lie in the evolution, ecology and systematics of Australian reptiles. A fundamental interest in these fascinating animals takes him into the field and the laboratory to learn more of their biology and to apply what he has learned in solving contemporary challenges for their conservation.

Arthur recently led the consortium to generate an annotated genome sequence for the Australian dragon lizard, Pogona vitticeps, which he and his team are using to probe the intricacies of sex determination in reptiles.

Appointments with guest speaker may be made via Beata Ujvari.

Beata U.

Title: Do cell-autonomous and non-cell-autonomous effects drive the structure of tumor ecosystems?

Authors: Tissot, T; Ujvari, B; Solary, E; Lassus, P; Roche, B; Thomas, F

Source: BIOCHIMICA ET BIOPHYSICA ACTA-REVIEWS ON CANCER, 1865 (2):147-154, APR 2016

Brief summary of the paper: By definition, a driver mutation confers a growth advantage to the cancer cell in which it occurs, while a passenger mutation does not: the former is usually considered as the engine of cancer progression, while the latter is not.

Actually, the effects of a given mutation depend on the genetic background of the cell in which it appears, thus can differ in the subclones that form a tumor. In addition to cell-autonomous effects generated by the mutations, non-cell-autonomous effects shape the phenotype of a cancer cell.

Here, we review the evidence that a network of biological interactions between subclones drives cancer cell adaptation and amplifies intra-tumor heterogeneity. Integrating the role of mutations in tumor ecosystems generates innovative strategies targeting the tumor ecosystem’s weaknesses to improve cancer treatment.

Strong representation by the WGG (Wild Genes Group) at the SMBE 2016 – the annual meeting of the Society for Molecular Biology and Evolution at the Gold Coast Convention & Exhibition Centre, Queensland, Australia (@OfficialSMBE).

A big ‘thank you’ to SMBE for awarding Kimberly Pinch and Nynke Raven with student travel awards and making it possible for them to attend SMBE 2016!

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Title: Anthropogenic selection enhances cancer evolution in Tasmanian devil tumours.

Authors: Beata Ujvari;  Anne-Maree Pearse; Kate Swift; Pamela Hodson; Bobby Hua; Stephen Pyecroft; Robyn Taylor; Rodrigo Hamede; Menna Jones; Katherine Belov; Thomas Madsen.

Source: Evolutionary Applications, Volume 7, Issue 2, pages 260–265, February 2014.

Brief summary of the paper: The Tasmanian Devil Facial Tumour Disease (DFTD) provides a unique opportunity to elucidate the long-term effects of natural and anthropogenic selection on cancer evolution.

Since first observed in 1996, this transmissible cancer has caused local population declines by >90%. So far, four chromosomal DFTD variants (strains) have been described and karyotypic analyses of 253 tumours showed higher levels of tetraploidy in the oldest strain.

We propose that increased ploidy in the oldest strain may have evolved in response to effects of genomic decay observed in asexually reproducing organisms. In this study, we focus on the evolutionary response of DFTD to a disease suppression trial.

Tumours collected from devils subjected to the removal programme showed accelerated temporal evolution of tetraploidy compared with tumours from other populations where no increase in tetraploid tumours were observed.

As ploidy significantly reduces tumour growth rate, we suggest that the disease suppression trial resulted in selection favouring slower growing tumours mediated by an increased level of tetraploidy.

Our study reveals that DFTD has the capacity to rapidly respond to novel selective regimes and that disease eradication may result in novel tumour adaptations, which may further imperil the long-term survival of the world’s largest carnivorous marsupial.