Scots pine (Pinus sylvestris L.) occupies a larger natural range than any other species from the whole Pinaceae family, extending from Europe to the Far East (Manchuria) through Siberia. Because of such a wide geographic spreading, with very different environmental conditions, and because of the long evolutionary history of this pine, a large intraspecific variation is expected to occur. The aim of this research is to study the genetic diversity within populations and the genetic differentiation between populations representative of the Italian and of the remaining Eurasian natural range of Scots pine. Until now 8 Italian populations, 22 populations from the rest of Europe (9 of which are French) and 1 from Asia (Turkey), for a total of 31 natural populations, were studied by using isozymes as genetic markers, analysed through horizontal starch gel electrophoresis. The obtained results confirm the previously observed sharp and outstanding differentiation of an Italian population, located in the Emilian Apennine, which is the most differentiated population by far: it is a relict and isolated remnant from glacial and postglacial migrations, and it is even less similar to the studied Italian Alpine populations than the remaining foreign populations, which tend to group together with them. These new observations supply further evidence of the status of important genetic resource for this small and autochthonous stand, whose differentiation could depend both on its origin from a different glacial refugium and on a different evolutionary history due to its peripheral position with respect to the main range of this species, and whose values of genetic diversity parameters are similar to those found in the other Italian populations, in spite of its geographic isolation. On the basis of the obtained values of genetic distance, the seven Italian populations from the Alps tend to group together and appear rather differentiated from the remaining ones, suggesting both a different postglacial origin and a relative genetic isolation due to the Alpine barrier, but their cluster is close to a group of French populations, suggesting a common origin and a subsequent differentiation. Other French populations are scattered along the dendrogram. Some hypotheses on the postglacial recolonization routes followed by this species are also discussed. The results of this research are increasing the available knowledge on Scots pine, making it possible the drafting of more accurate programmes of genetic resource conservation.

In the mitochondria and chloroplasts of flowering plants (angiosperms), transcripts of protein-coding genes are altered after synthesis so that their final primary nucleotide sequence differs from that of the corresponding DNA sequence. This posttranscriptional mRNA editing consists almost exclusively of C-to-U substitutions (direct) and less frequently of U-to-C substitution (reverse). Editing occurs predominantly within coding regions, mostly at isolated C residues, and usually at first or second positions of codons, thereby almost always changing the amino acid from that specified by the unedited codon. Editing may also create initiation and termination codons. The effect of C-to-U RNA editing in plants is to make proteins encoded by plant organelles more similar in sequence to their non plant homologs, then specific C-to- U editing events are essential for the production of functional plant mitochondrial proteins. Our attention has been devoted to the study of the mRNA editing in cox3 mitochondrial gene of fern Asplenium nidus. This study reveals the extreme importance of both C-to-U and U-to-C substitutions for protein expression. Keywords: mtDNA,