CLONING AND CHARACTERIZATION OF 2 CDNA CLONES ENCODING SEED-SPECIFIC ANTIMICROBIAL PEPTIDES FROM MIRABILIS-JALAPA L

We have isolated and characterized two cDNA clones (designated MJ1 and MJ2) encoding the two Mirabilis jalapa antimicrobial peptides (M(j)-AMP1 and M(j)-AMP2, respectively), which were previously purified from seeds of this plant species (Cammue et al. (1992), J Biol Chem 267: 2228-2233). In both cases, the deduced amino acid sequences reveal the presence of a putative signal sequence preceding the mature peptide, indicating that the M(j)-AMPs are expressed as preproteins. The M(j)-AMP1- and M(j)-AMP2-encoding genes are interrupted in their coding sequences by a single intron (380 bp and 900 bp for M(j)-AMP1 and M(j)-AMP2 genes, respecticely). Southern blot analysis indicates that the Mj-AMP-encoding genes belong to a gene family of low complexity. Northern blot analysis suggests seed-specific expression of M(j)-AMPs since transcripts of the expected size could only be detected in near-mature and in mature seeds of M. jalapa.