Foto del docente

Barbara Mantovani

Full Professor

Department of Biological, Geological, and Environmental Sciences

Academic discipline: BIO/05 Zoology

Research

Keywords: mtDNA Arthropoda satellite DNA mobile elements molecular phylogeny nuclear rDNA

Main research areas are: 1) Molecular animal taxonomy, systematics and phylogeny: mitochondrial and nuclear markers studies are utilized in  Arthropoda showing non canonical sexuality such as: i) Crustacea Branchiopoda Notostraca and Conchostraca (with instances of hermaphroditism, androdioeicy and parthenogenesis) ii) Insecta Isoptera (gonochoric but not panmictic because of their eusociality) iii) Insecta Siphonaptera (fleas with unbalanced sex ratio, sometimes embodying the bacterium Wolbachia pipientis, known as a host sexuality modifier). 2) Repetitive DNA sequence evolution: the molecular dynamics of repetitive sequences are analyzed in the nuclear genome of some of the above reported animal models through the study retrotransposons (R2, SINE) in order to determine their rate and mechanism of evolution with a particular attention to the concerted evolution theory ad to the library hypothesis.

1) Molecular animal taxonomy, systematics and phylogeny.

A) Owing to the wide array of sex distribution (gonochorism, hermaphroditism, unisexuality and androdioecy), Notostraca represent a model to study reproductive strategies variation and their effect on genetic structure. These Crustaceans also share a very ancient origin, the habitat (temporary pools) and the production of resistant stages. The order  Notostraca comprises only the two genera Triops e Lepidurus. The analyses of mt markers (12S e 16S) demonstrate a significant divergence of the Euroasiatic taxon  T. cancriformis with respect to American and Australian  Triops species, so that the possibility of a generic rank of differentiation has been suggested. For T. cancriformis, analyses have been widened to hypervariable markers (microsatellites). These have demonstrated that variability parallels reproductive modes in gonochoric and parthenogenetic populations, but not in the hermaphroditic ones. In Lepidurus, mt markers evidenced a consistent divergence between L. apus apus and L. apus lubbocki, taxa now considered as distinct species. In Southern Italy, the occurrence of the North-American and Asiatic taxon L. couesii has been demonstrated and a population genetic analysis performed.

B) In termites, mt analyses of Reticulitermes populations demonstrated the existence of many specific and subspecific entities in the eastern Mediterranean area, while for  Kalotermes flavicollis a consistent  genetic homogeneity has so far emerged. Hystory and biological traits can explain the scored differences between Reticulitermes spp. and Kalotermes populations whose genetic structuring is at present analyzed through interSINE and microsatellite markers.

2) Repetitive DNA sequence evolution: the molecular dynamics of repetitive sequences are analyzed in the nuclear genome of some of the above reported animal models through the study of rDNA, satellites and transposons in order to determine their rate and mechanism of evolution with a particular attention to the concerted evolution theory ad to the library hypothesis.

A) Structure and variability analyses of the IGS region in T. cancriformis confirms the existence of concerted evolution with higher variability scored in a tract external to a region with subrepeats; the most interesting datum is given by the absolute identity between subrepeats occupying the same position in different individuals/populations: the absence of a promoter sequence and subrepeat conservation suggest their possible role as enhancers. In L. dahalacensis a low copy number satellite flanking the 5SrDNA gene was isolated (LEP150). The pattern of variation observed is explained taking into account the presence at the LEP150 array borders of two loci under natural selection: the 5S rRNA gene, upstream, and the rDNA transcription promoter, downstream. These elements may drive the dynamics of flanking regions and linked repeats in a process similar to selective sweep. At variance of classical genetic hitchhiking, the selective sweep here scored should be realized and maintained through an interplay of selection and molecular drive.   In Reticulitermes a conserved and highly homogeneous satellite family (RET76) was isolated in all European taxa. Conservation and G-C richness suggest a possible non centromeric role. RET76 could be involved in the frequent chromosomal repatterning observed even in the same termite colony. Unfortunately, no comparisons are allowed since this is the first satellite isolated in Isoptera.

B) Mobile elements dynamics are at present analyzed with the study of the R2 retrotransposon which is a non-LTR, LINE, ancient retroelement that inserts specifically in the 28S gene of the ribosomal unit, following the recognition of a target sequence. Analyses are currently carried on in T. cancriformis populations with different sex distribution and in the eusocial system represented by Reticulitermes spp. In the latter, 4 new Short Interspersed Elements have been isolated and they are currently under study. Mobile element analyses will be extended to the taxa of the genus Bacillus (Insecta Phasmida) well known example of reticulate evolution.