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.
