Author: FERNANDO FEDER MOGUEL SALAZAR
Pathogenic microorganisms cause great losses annually and are a constant threat to agriculture and food production. The strategies used to control pathogen microorganisms' population such as spraying of fungicides, bactericides or insecticides are becoming ineffective as pathogens have being developing resistance against many of these compounds. Today, in agriculture there are serious concerns regarding the increasing volumes of pesticides that must be applied to control plant pathogens, and the environmental contamination. The development of safer and more efficient compounds to control plant pathogens is a demand that guarantees food production with the absence of residual pesticides. An opportunity that fulfills these criteria is represented by the antimicrobial peptides (AMPs), a class of small rich cysteine peptides with biological activities to kill fungi and bacteria. Sources for AMPs have been studied in animals and plants. However, it is clear that plants are an accessible and cheaper source for this kind of compounds. Many AMPs are produced in organs that are regarded as waste after plants' fruits or seeds have been harvested. AMPs from Chili pepper (Capsicum sp) have been extracted from leaves and seeds. The genes encoding AMP are being expressed in heterologous systems to explore the potential of these genes to protect the host against pathogens. In the present study, we carried out a review to highlight the work related with the production and cloning of AMPs from chili pepper. We also included our findings regarding the cloning of a defensin gene from habanero pepper leaves (Capsicum chinense Jacq) and the antimicrobial activity of some of their AMPs isolated from seeds.
Habanero chili pepper (Capsicum chinense) is widely consumed as a fresh vegetable, although its extremely high capsaicin content has led to other uses (e.g., medicine and self-defense). Recently described antimicrobial peptides from C. annuum were very efficient in inhibiting growth in human and plant pathogenic bacteria and fungi. In order to explore the potential use of Capsicum chinenseseeds as a source of antimicrobial peptides, in the present study a peptide fraction from C. chinense pepper seeds, denominated G10P1, was enriched, partially purified and its antimicrobial activitytested against the plant and human pathogens Xanthomonas campestris, Pseudomonas syringae, Pseudomonas aeruginosa, Erwinia carotovora, Agrobacterium sp., Shigella flexnerii, Escherichia coli, Staphyllococcus aureus and Bacillus subtilis. The minimum inhibitory concentration of the G10P1 peptide fraction against X. campestris was 12.5 μg mL-1. Electrophoresis of the G10P1 in a denaturant 15% polyacrylamide gel showed it to be composed of ~7.57 and ~5.6 kDa polypeptides, both associated with an area of strong antibacterial activity. The sequencing of 18 amino acids from the N-terminal of the ~7.57 peptides and 12 from the ~5.6 kDa peptides showed no clear association with previously described antimicrobial peptides. However, the ~5.6 kDa peptides were related to the NAC and WRKY transcription factors, both involved in direct regulation of the plant defense response against pathogen attack and the ~7.57 kDa peptides had low homology with a 3-oxo-[acyl-carrier-protein] synthase from Capsicum chinense.