Purification, Characterisation and cDNA Cloning of an Antimicrobial Peptide from Macadamia Integrifolia

Abstract

An antimicrobial peptide with no significant amino acid sequence similarity to previously described peptides has been isolated from the nut kernels of Macadamia integrifolia. The peptide, termed MiAMP1, is highly basic with an estimated pI of 10.1, a mass of 8.1 kDa and contains 76 amino acids including 6 cysteine residues. A cDNA clone containing the entire coding region corresponding to the peptide was obtained. The deduced amino acid sequence of the cDNA indicated a 26‐amino‐acid signal peptide at the N‐terminus of the preprotein. Purified MiAMP1 inhibited the growth of a variety of fungal, oomycete and gram‐positive bacterial phytopathogens in vitro. Some pathogens exhibited close to 100% inhibition in less than 1 μM peptide (5 μg/ml). Antimicrobial activity was diminished against most, but not all, microbes in the presence of calcium and potassium chloride salts (1 mM and 50 mM, respectively). MiAMPl was active against bakers yeast, was inactive against Escherichia coli and was non‐toxic to plant and mammalian cells. Analysis of genomic DNA indicated that MiAMP1 was encoded on a single copy gene containing no introns. The MiAMP1 gene may prove useful in genetic manipulations to increase disease resistance in transgenic plants.

A Novel Family of Small Cysteine-rich Antimicrobial Peptides from Seed of Impatiens balsaminaIs Derived from a Single Precursor Protein

“…The two remaining possible combinations of pairwise connectivities (i.e. Cys 6 -Cys 16 and Cys 7 -Cys 20 or Cys 6 -Cys 20 and Cys 7 -Cys 16 ,) could not be resolved by protease digestion methods. However, NMR has since been used to determine a solution structure for Ib-AMP1, enabling a comparison with that of the ␣-conotoxins, and will be reported elsewhere.…”

Specific Hypersensitive Response–Associated Recognition of New Apoplastic Effectors from Cladosporium fulvum in Wild Tomato

“…Of these, Ecp4, Ecp7, and Ecp29 (CTR) were found to share a Cys spacing profile with MiAMP1, a plant antimicrobial protein with a b/g-crystallin fold from nut kernels of M. integrifolia (Marcus et al 1997;McManus et al 1999). Purified MiAMP1 exhibits broad-spectrum inhibitory activity against several plant-pathogenic fungi, oomycetes, and gram-positive bacteria in vitro (Marcus et al 1997).…”

A Gene Encoding Scots Pine Antimicrobial Protein Sp-AMP2 (PR-19) Confers Increased Tolerance against Botrytis cinerea in Transgenic Tobacco

“…The combination of the broad spectrum action of MiAMP1 protein family members on numerous microorganisms [47,48] and the nature of the cysteine-rich AMPs, which reduce the growth of major microbes without any toxic effects toward the host [49], makes Sp-AMP proteins potential candidates for developing pathogen-resistant crops, a further demonstration of their role in tree resistance.…”