Characterization of a Bean (Phaseolus vulgaris L.) Malic‐enzyme Gene

Abstract

We have isolated a genomic clone encoding a plant NADP+‐dependent malic enzyme (NADP‐ME). This clone, isolated from bean (Phaseolus vulgaris L.), covers the entire gene (exons, introns) and 5′‐flanking regions. DNA sequencing defines 20 exons spanning approximately 4.5 kb, which range over 48–235 bp in size. All 19 introns are fairly small (79–391 bp). The first intron resides in the 5′‐untranslated leader sequence. Introns 10, 11 and 16 are located at positions identical to a rat malic‐enzyme gene. In the promoter region, a TATA box (TATATATA) is easily recognized 41 bp upstream of a single transcription‐initiation site. Two potential cis‐acting elements with homology to elements from plant genes, activated by UV light and fungal elicitors, were identified at positions −153 and −312, respectively. Southern‐blot analysis suggests a single gene copy, but also other distantly related genes, in the bean genome. The deduced NADP‐ME protein of 589 amino acids exhibits features consistent with a cytoplasmic location. We describe the organization of the NADP‐ME protein into functional domains located on separate exons. The evolution of malic‐enzyme genes coding for isoforms in different cellular compartments of plants and animals is discussed. Copyright © 1994, Wiley Blackwell. All rights reserved