Characterization of three members of the acc synthase gene family in Luptnus albus

ACC (1-aminocyclopropaue- 1-carboxylate) synthase is the key regulatory enzyme of the plant hormone eihylene biosynthetic pathway and is encoded by a multigene family in A.thaliana.. tomato, zucchini and other plants. Southern blot hybridizations show the presence of at least five ACC synthase genes in white lupin (L.albus) genome. Degenerate oligonucleotides corresponding to highly conserved regions were used as probes in the screening of the lupin genomic library (Vassilevskaia T.D., Ricardo C.P. and Rodrigues Pousada C.( 1993) Plant Mol Biol 22, 715-718). Two complete and one partial sequences representing different ACC synthase genes were isolated from the library. The coding region of LA-ACSl gene is interrupted by three introns and codes for a polypeptide of 487 arninoacid residues. RT-PCR studies indicate mostly rootspecific expression of this gene. LA-A(?S3gene contains two small introns with the positions corresponding to those of 1st and 3rd intron of LA-ACSL The predicted polypeptides for two genes share 50.1% identity. LA-ACS3 mRNA is present in hypocotyls of light- and dark-grown seedlings, young leaves, roots, flowers and green siliques. The 3.5-kb Xbal DNA fragment from ACC21.6 genomic clone has information for 295 arninoacid residues of another ACC synthase(LA-ACS2) showing 52.3% identity with 4th exon of LA-ACSl. The LA-ACS2 mRNA levels in hypocotyl tissue seem to be induced by wounding.