Biologia, Bratislava, 57/Suppl. 11: 191-196, 2002.

ISSN 0006-3088 (Biologia).

 

Full Paper

Structure of the of a-amylase genes in crustaceans and molluscs: evolution of the exon/intron organization.

 

Daniel Y. Sellos* & Alain Van Wormhoudt

Station de Biologie Marine du Museum National díHistoire Naturelle, BP 225, F-29900 Concarneau, France; tel.: ++ 33 2 98 97 06 59; fax: ++ 33 2 98 97 81 24; e mail: sellos@mnhn.fr

* corresponding author

Received: October 4, 2001 / Accepted: May 3, 2002

 

Abstract

a-Amylase is present in all groups of animals and characterized by an eight-stranded b/a-barrel three-dimensional structure. The exon-intron organization of the gene is highly variable with respect to the number of introns and the location of the junctions. Phylogeny, inferred from the structure of the gene, cDNA or amino-acid sequences including information from marine invertebrates, revealed interesting results especially concerning the proposed position of Drosophila, particularly since the structure of their genes reveals one or no intron. Different hypothesis could be suggested, such as the disappearance of introns during evolution of the insect group with specific and (or) rapid adaptation to new substrates. Intron positions were determined in crustaceans and in molluscs. Among Arthropoda, Crustacean penaeids are very ancient, as they were already present in the Devonian period. The complex structure of their a-amylase genes revealed the presence of nine introns. The position and phase of some of these introns are also seen in insects. Two are also present in Ceratitis. One or no intron is usually observed in the Drosophila family. In the bivalve mollusc, Crassostrea gigas, we have determined that the gene contains seven introns. Changes in the location of intron insertion are reported mainly in the 5í end of the genes and are discussed. Many introns from one gene having no counterpart in the others, seemed to have appeared later in evolution at a non-specific position at the end of the gene. More observations however are necessary to confirm these hypotheses, taking into account other members of the a-amylase family from more primitive eukaryotes in different groups such as poriferes, cnidaires, ecdysozoa and lophotrochozoa.

 

Key words: amylase, gene, evolution, adaptation, invertebrates, marine, populations.