Identification and characterization of a full-length cDNA encoding for an auxin-induced 1-aminocyclopropane-1-carboxylate synthase from etiolated mung bean hypocotyl segments and expression of its mRNA in response to indole-3-acetic acid

1-Aminocyclopropane-1-carboxylate (ACC) synthase (EC 4.4.1.14) is the key regulatory enzyme in the ethylene biosynthetic pathway. The identification and characterization of a full-length cDNA (pAIM-1) 1941 bp in length for indole-3-acetic acid (IAA)-induced ACC synthase is described in this paper. The pAIM-1 clone has an 87 bp leader and a 402 bp trailing sequence. The open reading frame is 1452 bp long encoding for a 54.6 kDa polypeptide (484 amino acids) which has a calculated isoelectric point of 6.0. In vitro transcription and translation experiments support the calculated molecular weight and show that the enzyme does not undergo processing. Eleven of the twelve amino acid residues which are conserved in aminotransferases are found in pAIM-1. The sequence for pMAC-1 which is one of the 5 genes we have identified in mung bean is contained in pAIM-1. pAIM-1 shares between 52 to 65% homology with previously reported sequences for ACC synthase at the protein level. There is little detectable pAIM-1 message found in untreated mung bean tissues; however, expression is apparent within 30 min following the addition of 10 μM IAA reaching a peak after approximately 5 h with a slight decrease in message after 12 h. These changes in message correlate with changes in ACC levels found in these tissues following treatment with 10 μM IAA

Identification and characterization of three putative genes for 1-aminocyclopropane-1-carboxylate synthase from etiolated mung bean hypocotyl segments

The polymerase chain reaction (PCR) was used to produce 3 putative clones for ACC synthase from etiolated mung bean (Vigna radiata Rwilcz cv. Berken) hypocotyls. This was accomplished by utilizing genomic DNA from mung bean and degenerate primers made from information derived from highly conserved regions of ACC synthase from different plant tissues. The total length of pMAC-1, pMAC-2 and pMAC-3 are 308, 321, and 326 bp, respectively, all of which code for 68 amino acids. The introns for pMAC-1, pMAC-2 and pMAC-3 are 92, 105, and 110 bp, respectively. The degrees of homology at the DNA level for each of these clones is ca. 80% in their coding region and ca. 50% in their respective introns. This is the first report providing evidence that there are at least 3 genes for ACC synthase in etiolated mung bean

Identification of two new members of the l-aminocyclopropane-l-carboxylate synthase-encoding multigene family in mung bean

The key enzyme regulating ethylene biosynthesis in higher plants is l-aminocyclopropane-l-carboxylate (ACC) synthase. In mung bean (MB), the existence of three genes encoding this enzyme has previously been reported [Botella et al., Plant Mol. Biol. 18 (1992) 793-797], one of which corresponds to a full-length indole-3-acetic acid-inducible cDNA [Botella et al., Plant Mol. Biol. (1992) 425-436], In this paper we report the cloning of two new genomic sequences coding for ACC synthase in MB (MAC-4 and MAC-5). MAC-4 is 1340 bp long and encodes 388 amino acids (aa) while MAC-5 is 1393 bp long and encodes for 391 aa. Genomic Southern analysis suggests the existence of only one copy of each gene in the genome