Pires-daSilva A (2007) Semin Cell Dev Biol "Evolution of the control of sexual identity in nematodes."

Pires-Dasilva A

[Semin Cell Dev Biol, 2007]

Most animals are male/female species and reproduce sexually. Variation in this pattern of reproduction has arisen many times during animal evolution, particularly in nematodes. Little is known about the evolutionary forces and constraints that influenced the origin of self-fertilization, for instance, a type of reproduction that seems to have evolved many times in the phylum Nematoda. Caenorhabditis elegans, a very well known nematode, provides the framework for comparative studies of sex determination. The relative ease with which nematodes can be studied in the laboratory and the fact that many recently developed techniques can be applied to many species make them attractive for comparative research. It is relatively poorly understood how the evolution of new types of sex determination and mode of reproduction results in changes in genome structure, ecology and population genetics. Here, I review the evolution of sex determination and mating types in the phylum Nematoda with the objective of providing a framework for future research.

Pires-daSilva A et al. (2003) Nature Reviews Genetics "The evolution of signalling pathways in animal development."

Sommer RJ, Pires-Dasilva A

[Nature Reviews Genetics, 2003]

Despite the bewildering number of cell types and patterns found in the animal kingdom, only a few signalling pathways are required to generate them. Most cell-cell interactions during embryonic development involve the Hedgehog, Wnt, transforming growth factor-beta, receptor tyrosine kinase, Notch, JAK/STAT and nuclear hormone pathways. Looking at how these pathways evolved might provide insights into how a few signalling pathways can generate so much cellular and morphological diversity during the development of individual organisms and the evolution of animal body

Pires-daSilva A et al. (2004) Genes Dev "Conservation of the global sex determination gene tra-1 in distantly related nematodes."

Sommer RJ, Pires-Dasilva A

[Genes Dev, 2004]

Sex determination has long intrigued evolutionists, geneticists, and developmental biologists in a similar way. Substantial evidence indicates that sex determination evolves rapidly and, therefore, can be used to study how molecular patterning processes evolve. In Caenorhabditis elegans, sex determination relies on a signaling pathway that involves a cascade of negatively acting factors, finally triggering the GLI-family zinc-finger transcription factor TRA-1. We have started to investigate sex determination in the nematode satellite species Pristionchus pacificus that is separated from C. elegans for 200-300 million years. In P. pacificus, animals with two X chromosomes develop as hermaphrodites, whereas XO animals develop as males. We used an unbiased forward genetic approach and isolated several mutants with a hermaphrodite to male transformation of the XX karyotype. We identified one complementation group as representing the P. pacificus ortholog of tra-1, providing the first evidence for the conservation of a global sex determination gene over a time period of at least 200 million years. A Ppa-tra-1 morpholino phenocopies Ppa-tra-1 mutants an

Pires-daSilva A et al. (2003) Dev Cell "Finally, worm polycomb-like genes meet Hox regulation."

Pires-Dasilva A, Sommer RJ

[Dev Cell, 2003]

Polycomb and Trithorax group proteins have been shown to regulate Hox gene expression in files and mammals, but not in worms. Two reports in this issue of Developmental Cell establish a first link between Polycomb-like genes and Hox gene regulation in C. elegans. However, sequence comparison indicates that these genes may not be homologous to the fly Polycomb genes, suggesting that independent gene recruitment occurred during nematode evolution.

Andre Pires-daSilva et al. (2002) Mid-west Worm Meeting "Evolution of sex determination mechanisms in nematodes"

Andre Pires-daSilva, Ralf J Sommer

[Mid-west Worm Meeting, 2002]

We are studying the evolution of genetic pathways, using sex determination in nematodes as a model. The hallmark of sex determination is that the final result of the pathway is the same throughout evolution: the production of males and females. Detailed genetic and molecular analysis in Drosophila and C. elegans indicate that this pathway evolves very rapidly, making it an excellent model to study how developmental mechanisms and pathways evolve. Although there is low structural conservation for many sex determination genes in the Rhabditidae familiy, recent studies suggest that the function of some these genes in somatic sex determination is conserved. We are taking a genetic approach to study the sex determination pathway in a nematode of the Diplogasteridae family, Pristionchus pacificus. We would like to know whether in this more distantly related nematode there is conservation in the mode of sex determination. We performed a pilot screen of 1500 gametes and isolated 8 putative transformers. Although the soma is almost completely transformed to a male phenotype (development of spicules, rays and bursa in the tail and an one-armed gonad), using molecular markers we have determined that two of them have a XX genotype. These transformers show no mating behaviour and the germ line may exhibit increased cell death. Both transformers map to P. pacificus linkage group III, which show regions of synteny with C. elegans chromosome III. tra-1, the terminal sex determination gene of C. elegans is located on C. elegans chromosome III. We cloned Ppa-tra-1 and generated a polymorphic marker for this gene. There is strong linkage between the Ppa-tra-1 marker and the two transformers. Further molecular characterization is in progress.

Ancell H et al. (2017) Semin Cell Dev Biol "Sex-specific lifespan and its evolution in nematodes."

Ancell H, Pires-Dasilva A

[Semin Cell Dev Biol, 2017]

Differences between sexes of the same species in lifespan and aging rate are widespread. While the proximal and evolutionary causes of aging are well researched, the factors that contribute to sex differences in these traits have been less studied. The striking diversity of nematodes provides ample opportunity to study variation in sex-specific lifespan patterns associated with shifts in life history and mating strategy. Although the plasticity of these sex differences will make it challenging to generalize from invertebrate to vertebrate systems, studies in nematodes have enabled empirical evaluation of predictions regarding the evolution of lifespan. These studies have highlighted how natural and sexual selection can generate divergent patterns of lifespan if the sexes are subject to different rates or sources of mortality, or if trade-offs between complex traits and longevity are resolved differently in each sex. Here, we integrate evidence derived mainly from nematodes that addresses the molecular and evolutionary basis of sex-specific aging and lifespan. Ultimately, we hope to generate a clearer picture of current knowledge in this area, and also highlight the limitations of our understanding.

Jagan Srinivasan et al. (2002) Worm Breeder's Gazette "Towards a Pristionchus genome map II - Microevolutionary analysis of the nematode genus Pristionchus"

Ralf J Sommer, Min Zheng, Isabel Kipping, Arturo Gutierrez, Andre Pires da Silva, Hanh Witte, Jagan Srinivasan

[Worm Breeder's Gazette, 2002]

We describe the molecular characterization of laboratory strains of the nematode genus Pristionchus , which lays a foundation for microevolutionary analyses of vulva development. We isolated 13 laboratory strains of the Pristionchus genus that are derived from natural isolates from around the world. Mating experiments and ITS sequence analysis indicated that these 13 strains represent four different species; the gonochoristic species P. lheritieri and three hermaphroditic species, P. pacificus , P. maupasi and an as yet undescribed species Pristionchus sp., respectively. P. pacificus is represented by five different strains isolated from California, Washington, Hawaii, Ontario and Poland. Our working 'wild type' strain is the California strain. Since polymorphisms are becoming an important tool in modern day genomic analysis, which facilitate cloning of mutations, we decided to search for polymorphisms in the various Pristionchus pacificus strains. We performed amplified restriction fragment length polymorphism (AFLP) analyses of the different P. pacificus strains and found that the American strains are highly polymorphic (Srinivasan et al., 2001). We observed the largest genetic variation between the strain from California on the one hand and Washington and Hawaii on the other hand. In contrast, the developmentally distinct strain from Poland is identical to the Californian strain. Hence, we chose the Washington strain as our polymorphic strain for future experiments. These results provide us a framework for further studies on microevolution in developmental processes. Reference: Srinivasan, J., Pires-daSilva, A.; Gutierrez, A.; Jungblut, B.; Zheng, M.; Witte, H.; Schlak., I. & Ralf J. Sommer, Evolution & Development (2001) 3 : 229-240.

Carvalho S et al. (2006) EMBO Rep "The world of a worm: a framework for Caenorhabditis evolution. Workshop on the study of evolutionary biology with Caenorhabditis elegans and closely related species."

Carvalho S, Pires-Dasilva A, Barriere A

[EMBO Rep, 2006]

Shakes DC et al. (2011) Nat Commun "Asymmetric spermatocyte division as a mechanism for controlling sex ratios."

Pires-Dasilva A, Shakes DC, Huynh H, Neva BJ, Chaudhuri J

[Nat Commun, 2011]

Although Mendel's first law predicts that crosses between XY (or XO) males and XX females should yield equal numbers of males and females, individuals in a wide variety of metazoans transmit their sex chromosomes unequally and produce broods with highly skewed sex ratios. Here, we report two modifications to the cellular programme of spermatogenesis, which, in combination, help to explain why males of the free-living nematode species Rhabditis sp. SB347 sire <5% male progeny. First, the spermatogenesis programme involves a modified meiosis in which chromatids of the unpaired X chromosome separate prematurely, in meiosis I. Second, during anaphase II, cellular components essential for sperm motility are partitioned almost exclusively to the X-bearing sperm. Our studies reveal a novel cellular mechanism for the differential transmission of X-bearing sperm and suggest Rhabditis sp. SB347 as a useful model for studying sex chromosome drive and the evolution of new mating systems.

Kim, J. et al. (2017) International Worm Meeting "Evolution of a novel behavior of Auanema freiburgensis, tube-nictation."

Kim, J., Adams, S., Lee, J., Kim, S., Pires-daSilva, A., Tandonnet, S.

[International Worm Meeting, 2017]

Nematodes can be a good model for evolution of novel traits because they have extremely divergent phenotypes. We are interested in the question of how a novel trait emerges and evolves, which is one of the fundamental questions in evolutionary biology. To answer this question, we use a new species of nematodes, A. freiburgensis. This nematode shows nictation behavior, a dispersal behavior, and interestingly, it can use its own cuticle of the previous molt for tail support instead of fungi or any rough surface, which is the case of C. elegans. To understand how changes in the genome affect evolution of this new behavior, we are sequencing its genome and planning to perform forward and reverse genetics.