ISOLATION AND CHARACTERIZAZACTION OF AN EXPANSIN GENE FROM Melilotus alba.

GIORDANO W.; RIVELLI ANTONELLI J.; HIRSCH AM.

Mendoza, Argentina.

Congreso; XXI Annual Scientific Meeting of the Cuyo Biology Society.; 2003

Sociedad de Biología de Cuyo

Expansins are cell wall proteins that play a key function in basic processes of plant growth and differentiation. Reverse transcription?polymerase chain reaction was used to detect expansin gene expression in white sweetclover (Melilotus alba) after treatment with Sinorhizobium meliloti. A BLAST search of the GenBank database using several of the clones obtained revealed a 537 bp sequence with very strong similarity to the a-expansin gene in legumes. A full-length sweetclover expansin sequence (MaEXP1) was obtained using 5?- and 3? rapid amplification of cDNA end cloning, and the deduced amino acid sequence (MaEXP1) was highly conserved relative to those of legume a-expansins. There is little similarity in the first 25 residues of the peptide sequence, which constitutes the signal peptide predicted with the Signal P program. The mature protein (232 amino acid residues) contains at the carboxyl terminus four conserved tryptophans whose spacing resembles that of tryptophans in the cellulose-binding domains of cellulase.  This region may be responsible for expansin binding to cellulose and related wall glycans. A model with the three probable domains in expansin protein (a classical signal peptide, a central catalytic domain and a putative cellulose-binding domain at the carboxy-terminus) is postulated for MaEXP1.