Analisi della struttura genomica diArabidopsis thalianaL.

The present thesis provides an insight on the genomic structure of plant species, by taking in exam the model organism Arabidopsis thaliana. The research activity pointed towards three directions. Initially the correlation between the expression profile and some structural properties such as the sequence length and the GC (guanine + cytosine) content was studied. The results revealed that in plants highly expressed genes undergo a selection for miniaturization which is probably due to the need to minimize the cost of the transcription/translation process. In a successive phase the usage of the synonymous codons (i.e. nucleotide triplettes which code for the same amino acid) was investigated within 15 Arabidopsis tissues. The results showed that genes specifically expressed in certain tissues use a definite set of codons, whereas more widely expressed genes feature a codon composition which is, at a certain extent, a compromise between the codons used in the single tissues. Finally the nucleotide composition as a function of the position in the gene was studied in two monocots and two dicots. For all the analyzed bases compositional gradients were revealed. The observed trends, mostly describable with a linear model, underlined marked difference between monocots and dicots.