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 - 4.42

ORTHOLOGOUS SEQUENCES OF A TRYPSIN INHIBITOR GENE IN SPECIES OF LENS MILL.

SONNANTE G.*, DE PAOLIS A.**, PIGNONE D.*

* CNR - Istituto del Germoplasma, Bari

** CNR - Istituto di Scienze delle Produzioni Alimentari (ISPA), Sez. di Lecce

Lens culinaris subsp. culinaris, wild relatives, trypsin inhibitor, sequence polymorphism

Most plant species show the presence of proteinase inhibitors. These are ubiquitous proteins, considered to be part of the natural defence mechanisms against the aggression of insects, nematodes and other predators. The interest in these proteins is mainly due to their role in host-pathogen co-evolution or in the regulation of endogenous enzymes, but they are also excellent indicators of plant evolution and diversity. With the aim of identifying new orthologous genes for the trypsin inhibitor (TI), a survey of various taxa of the genus Lens was started.

Forward and reverse nucleotide primers were designed in different positions, taking as a model the conserved aminoacid sequence of the trypsin inhibitor from Pisum sativum L. as reported in the EMBL database. The different primer combinations were tested for DNA amplification in lentil (Lens culinaris subsp. culinaris ) and its wild relatives. In general, the cultigen and the other wild relatives produced a similar amplification product derived from each of the primer combinations used. However, in some cases, L. nigricans showed no amplification product at all, or one of a different size. The primers which were able to amplify the longest region of TI gene were selected for the amplification of all the material used in the analysis. The fragments obtained were then purified and directly sequenced. Very few nucleotide differences were observed between the cultigen and its wild relatives, except for L. nigricans , which showed a relatively high number of nucleotide substitutions. This observation is in agreement with other molecular evidence according to which L. nigricans is considered the most divergent species within the genus. Amplified orthologous sequences were translated in silico and, notwithstanding some aminoacid substitutions, the predicted active sites for trypsin and chymotrypsin inhibitors are conserved in all the species analysed. Data on the activity of these novel inhibitors can only come from in vivo expression of these orthologous sequences.