Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Poster Abstract - 4.45

POLYMORPHISM OF PHYTOCHROME A GENE PROMOTERS IN NICOTIANA TABACUM CULTIVARS

INTRIERI M.C.*^,**, SABATINI A.**, MULEO R.*^,**, BUIATTI M.**

*) Dipartimento di Produzione Vegetale, Università della Tuscia, VT

**) Dipartimento di Biologia Animale e Genetica, Università di Firenze, FI

Phytochrome A, Nicotiana tabacum, promoter evolution

N. tabacum, a widely cultivated allopolyploid species, is a classical case study of genetic and both traditional and biotechnological approaches in plant breeding. Allopolyploids are hybrids whose genome contains a complete set of chromosome from each parental species. Numerous N. tabacum cultivars are cultivated and are defined to by area of production, method of curing, morphological and chemical differences, and by manufacturing processors. Previous studies noted that, despite large difference in morphology and growth characteristic, molecular marker recognised a relatively small polymorphism among cultivars.

In this study we analysed the phytochromes A (phyA1, phyA2) promoter sequences of some N. tabacum cultivars with the aim to ascertain weather the two copy of phyA, in tobacco genome, are paralogues or orthologues and to evaluate the rate of variation of each sequences. The two promoters of tobacco phyA, previous characterised in SR1 genotipe by GUS fusion experiments, have been isolated and sequenced in cultivars chosen by their own difference in many characters.

We have demostrated that the two phyA present in N. tabacum genome are orthologues derived from progenitors from two progenitors as shwon the phyA promoter sequences of the putative ancestrals, N. tomentosiformis (T) and N. sylvestris (S). The sequences obtained from N. tabacum confirm that in all cultivars both sequences are present, and both copies, phyA1 and phyA2, evolve with different rate of variation, and the cluster trees obtained from aligned sequences show a clear separation between the copies coming from the two parental subgenomes, S and T. It is worth noting, that the rate of variation is very low in the phyA2, while a higher rate of variation is shown in the phyA1 sequence. Looking close to the type of mutation found, it appears that the common mutation are SNPs and small insertion/deletion (1/2bp), even thought larger deletion/insertion are also present. Genes duplicated by polyploidy may retain their original or similar function, undergo diversification in protein function and regulation or one copy may become silenced through mutational or epigenetic means. Duplicated genes may also interact through inter locus recombination, gene conversion or concerted evolution. Regards to the tobacco phyAs, from literature is known that are active promoters, both regulated by light; moreover, from our results we speculate that the difference in the frequency of mutations is not insignificant from a biological point of view, and the next challange it will be the study of the dynamic of the expression of the two copies, and the derived information will be usable in the programme of plant improvement.