Marco Pellecchia

Mitochondrial genomes of extinct aurochs survive in domestic cattle

Archaeological and genetic evidence suggest that modern cattle might result from two domestication events of aurochs (Bos primigenius) in southwest Asia, which gave rise to taurine (Bos taurus) and zebuine (Bos indicus) cattle, respectively [1,2,3]. However, independent domestication in Africa [4,5] and East Asia [6] has also been postulated and ancient DNA data raise the possibility of local introgression from wild aurochs [7,8,9]. Here, we show by sequencing entire mitochondrial genomes from modern cattle that extinct wild aurochsen from Europe occasionally transmitted their mitochondrial DNA (mtDNA) to domesticated taurine breeds. However, the vast majority of mtDNAs belong either to haplogroup I (B. indicus) or T (B. taurus). The sequence divergence within haplogroup T is extremely low (eight-fold less than in the human mtDNA phylogeny [10]), indicating a narrow bottleneck in the recent evolutionary history of B. taurus. MtDNAs of haplotype T fall into subclades whose ages support a single Neolithic domestication event for B. taurus in the Near East, 911 thousand years ago (kya).

Feminizing Wolbachia in Zyginidia pullula (Insecta, Hemiptera), a leafhopper with an XX/X0 sex-determination system

Zyginidia pullula is a grass-dwelling leafhopper characterized by a bisexual reproduction mode. In this species, some females collected in Northern Italy, when mated with males, gave origin to an exclusively female brood. Here, we demonstrated that in these lineages an infection by a new strain of Wolbachia pipientis—designated as wZygpul—was detected by amplifying and sequencing the wsp and 16S rRNA genes. About half of the female progeny were characterized by intersexual phenotypes, i.e. showing upper pygofer appendages, a typical male secondary sexual feature. The karyological analysis proved that while phenotypically normal females had a female genotype, those with upper pygofer appendages had a male genotype and were thus feminized males. The complete removal of W. pipientis after tetracycline treatment of morphologically normal females, and the consequent re-appearance of males in the brood, permitted us to connect the feminizing effect with the presence of the bacterium. This is the first case of feminization by W. pipientis in an XX/X0 sex-determination system, and is the second case reported in insects.

Genetic diversity in widespread species is not congruent with species richness in alpine plant communities

The Convention on Biological Diversity (CBD) aims at the conservation of all three levels of biodiversity, that is, ecosystems, species and genes. Genetic diversity represents evolutionary potential and is important for ecosystem functioning. Unfortunately, genetic diversity in natural populations is hardly considered in conservation strategies because it is difficult to measure and has been hypothesised to co-vary with species richness. This means that species richness is taken as a surrogate of genetic diversity in conservation planning, though their relationship has not been properly evaluated. We tested whether the genetic and species levels of biodiversity co-vary, using a large-scale and multi-species approach. We chose the high-mountain flora of the Alps and the Carpathians as study systems and demonstrate that species richness and genetic diversity are not correlated. Species richness thus cannot act as a surrogate for genetic diversity. Our results have important consequences for implementing the CBD when designing conservation strategies.

The mystery of Etruscan origins: novel clues from Bos taurus mitochondrial DNA

The Etruscan culture developed in Central Italy (Etruria) in the first millennium BC and for centuries dominated part of the Italian Peninsula, including Rome. The history of the Etruscans is at the roots of Mediterranean culture and civilization, but their origin is still debated: local or Eastern provenance? To shed light on this mystery, bovine and human mitochondrial DNAs (mtDNAs) have been investigated, based on the well-recognized strict legacy which links human and livestock populations. In the region corresponding to ancient Etruria (Tuscany, Central Italy), several Bos taurus breeds have been reared since historical times. These breeds have a strikingly high level of mtDNA variation, which is found neither in the rest of Italy nor in Europe. The Tuscan bovines are genetically closer to Near Eastern than to European gene pools and this Eastern genetic signature is paralleled in modern human populations from Tuscany, which are genetically close to Anatolian and Middle Eastern ones. The evidence collected corroborates the hypothesis of a common past migration: both humans and cattle reached Etruria from the Eastern Mediterranean area by sea. Hence, the Eastern origin of Etruscans, first claimed by the classic historians Herodotus and Thucydides, receives strong independent support. As the Latin philosopher Seneca wrote: Asia Etruscos sibi vindicat (Asia claims the Etruscans back).

Sex and stripping: The key to the intimate relationship between Wolbachia and host?

Wolbachia pipientis is known to infect only arthropods and nematodes (mainly filarial worms). A unique feature shared by the two Phyla is the ability to replace the exoskeleton, a process known as ecdysis. This shared characteristic is thought to reflect a common ancestry. Arthropod moulting is induced by the steroid hormone 20-hydroxyecdysone (20E) and a role for ecdysteroids in nematode ecdysis has also been suggested. Interestingly, Wolbachia removal in filarial worms is detrimental to the host that is subjected to an impaired development. From analyses of the genome of Wolbachia harboured by the filarial nematode Brugia malayi and that of its host, the bacterium may provide a source of heme, an essential component of cytochromes P450 that are necessary for biosynthetic pathways of steroid hormones. In arthropods, Wolbachia is a reproductive manipulator, inducing various phenotypic effects that may be due to differences in host physiology, and in particular to endocrine-related processes governing development and reproduction. At this regard, insect steroids have a well-defined role in the coordination of multiple developmental processes, and in adults they control important aspects of reproduction, including ovarian development, oogenesis, sexual behaviour, and in some taxa vitellogenin biosynthesis. According to some authors ecdysteroids may also act as sex hormones. In insect sex differentiation is generally thought to be a strictly genetic process, where each cell decides its own sexual fate based on its sex chromosome constitution, but, surprisingly, recent data demonstrate that in Drosophila sex determination is non cell-autonomous, as it happens in mammals. Thus the presence of signals coordinating the development of a gender-specific phenotype cannot be excluded. This could explain why Wolbachia interferes with insect reproduction; and also could explain why Wolbachia interferes with insect development. Thus, is “sex (= reproduction) and stripping (= ecdysis)” the key to the intimate relationship between Wolbachia and its host?

Honey Bees (Apis mellifera, L.) as Active Samplers of Airborne Particulate Matter

Honey bees (Apis mellifera L.) are bioindicators of environmental pollution levels. During their wide-ranging foraging activity, these hymenopterans are exposed to pollutants, thus becoming a useful tool to trace the environmental contaminants as heavy metals, pesticides, radionuclides and volatile organic compounds. In the present work we demonstrate that bees can also be used as active samplers of airborne particulate matter. Worker bees were collected from hives located in a polluted postmining area in South West Sardinia (Italy) that is also exposed to dust emissions from industrial plants. The area is included in an official list of sites of national interest for environmental remediation, and has been characterized for the effects of pollutants on the health of the resident population. The head, wings, hind legs and alimentary canal of the bees were investigated with Scanning Electron Microscopy coupled with X-ray spectroscopy (SEM-EDX). The analyses pointed to specific morphological and chemical features of the particulate, and resulted into the identification of three categories of particles: industry -, postmining -, and soil –derived. With the exception of the gut, all the analyzed body districts displayed inorganic particles, mostly concentrated in specific areas of the body (i.e. along the costal margin of the fore wings, the medial plane of the head, and the inner surface of the hind legs). The role of both past mining activities and the industrial activity close to the study area as sources of the particulate matter is also discussed. We conclude that honey bees are able to collect samples of the main airborne particles emitted from different sources, therefore could be an ideal tool for monitoring such a kind of pollutants.

Sex Steroids in Insects and the Role of the Endosymbiont Wolbachia:A New Perspective

Sex steroids play a pivotal role in sex differentiation and sex reversal in several species of vertebrates, both with genotypic and environmental sex determination systems (Nakamura, 2010; Norris & Carr, 2006). Steroidal sex hormones can be found naturally in both sexes of vertebrates, although the proportions of hormones may differ between males and females. Feminization of males or masculinization of females can be induced by altering the levels of ‘female’ and ‘male’ hormones, respectively. Estrogens for example have a feminizing effect on gonadal differentiation in many species of fish, amphibians, reptiles, and birds (Guiguen et al., 2010; Nakamura, 2009, 2010). In humans, androgen receptor defect disorder may lead to gonadal feminization and, in its complete form, the syndrome causes sex reversal of genotypical (XY) males and a female phenotype (Oakes et al., 2008). Vertebrate-like sex steroids occur in several groups of invertebrates including nematodes, arthropods, echinoderms, but full information on the precise action and function of sex steroids is still missing (Janer & Porte, 2007). Some intriguing data have been provided in mollusks, where an involvement of steroids in gender determination and sexual differentiation of the brain, and even in a “superfeminization syndrome”, has been demonstrated (Oehlmann et al., 2006; Wang & Croll, 2004). In insects the existence of sex hormones is under debate. Indeed sex differentiation is generally thought to be a strictly genetic process, in which each cell decides its own sexual fate autonomously, based on its sex chromosome constitution. Therefore, differentiation of primary and secondary sexual characteristics should be exclusively under the control of the genotype of each single cell (Schutt & Nothiger, 2000; Steinmann-Zwicky et al., 1989). This hypothesis was born studying insect gynandromorphs, i.e. aberrant specimens with an intermediate feature between female and male (according to the Greek roots gyne = female, aner = male, morphe = form; Fig. 1). In the fruit fly Drosophila melanogaster, gynandromorphs may arise when one embryonic nucleus loses an X chromosome and the insects possess a mixture of XX (i.e. female) and X0 (i.e. male) tissues. According to Gilbert (2000), because there are no sex hormones in insects to modulate such events, each cell makes its own sexual “decision”.

Pattern of ancient goat migration revealed by AFLP molecular markers

Riassunto I marcatori AFLP ricostruiscono gli spostamenti di Capra hircus al seguito delle antiche migrazioni umane. Capra hircus è adattabile a condizioni ambientali molto differenti e possiede un areale di distribuzione estremamente ampio. Studi recenti suggeriscono che la capra abbia giocato un ruolo chiave nel sostentamento delle popolazioni umane durante le migrazioni demiche verso ovest, successive alla rivoluzione agricola del Neolitico. Lo studio della variabilità genetica di questa specie può quindi essere un utile strumento sia per ricostruire le antiche migrazioni umane, sia per preservare la diversità biologica di razze storiche e localmente adattate. L’analisi statistica dei marcatori AFLP effettuata su 44 razze autoctone (campionate in Europa, Medio Oriente, Anatolia) e 2 cosmopolite, affiancata da metodi di interpolazione geografica, ha permesso di evidenziare: - la peculiare composizione genetica delle razze Orobica e Tauernshecken (entrambe di origine incerta) rispetto ai popolamenti europeo e medio-orientale; - un significativo gradiente di distribuzione delle distanze genetiche tra razze che da sud-est procede verso nord-ovest, sovrapponibile al modello di variazione genetica umana, probabile traccia di almeno due differenti eventi di migrazioni umane lungo la via di espansione neolitica dell’agricoltura.

Detecting footprints of selection in Ovis aries by a spatial analysis approach

Abstract Detecting adaptive loci in the genome is essential as it gives the possibility to understand what proportion of a genome or which genes are under the pressure of natural selection. In this paper, we used a Spatial Analysis Method (SAM) recently developed to detect signatures of natural selection in sheep breeds. With the contribution of Geographical Information Systems, environmental variables, and AFLP data, multiple univariate logistic regressions are run to test for association between allelic frequencies at marker loci and environmental variables. The results of the application of this method to sheep breeds are compared with those obtained with a standard population genetics approach.

Mitochondrial DNA diversity of five Italian autochtonous donkey breeds

Abstract To investigate the mitochondrial DNA diversity of five Italian donkey breeds (Amiata, Martinafranca, Romagnolo, Asinara, and Ragusano), we sequenced the HVR I region (D-loop, 288 bp) and cytochrome b gene (274 bp) in 121 individuals. In the D-loop we found nineteen mutations corresponding to fourteen different haplotypes, while in cyt b coding gene only six mutations were found, originating five different haplotypes. In particular, three mutations out of six were non-synonymous, causing an aminoacidic substitution. About the D-loop region, the value of nucleotide diversity (π) observed within breeds was relatively low, but not far from values detected in other European breeds. Phylogenetic and network analyses disclosed the presence of two divergent maternal lineages within Italian donkeys. These haplogroups correspond to the well known lineages of ancestors (Equus asinus somaliensis and E. a. africanus), as donkeys were domesticated from distinct wild subspecies living in Eastern Africa regions. In four of the investigated breeds we detected the presence of both mtDNA lineages, while Amiata donkeys were characterized by mitochondrial haplotypes belonging to the E. a. somaliensis lineage only. The genetic relationships between the Italian populations are discussed and interpreted according to the most recent bibliographic data.