Antimicrobial peptides and immunolocalization of a LTPin Vigna unguiculata seeds

Two cysteine-rich antimicrobial peptides (6.8 and 10 kDa) were isolated from cowpea (Vigna unguiculata) seeds and shown to deter development, in an in vitro assay, of the phytopathogenic fungi Fusarium oxysporum and F. solani and the yeast Saccharomyces cerevisiae. The peptides purified by RP-HPLC were submitted to automated N-terminal amino acid sequencing. Sequence analysis of these peptides showed the presence of a defensin and a lipid transfer protein (nsLTP) with high degree of homology to other antifungal peptides isolated from plants. LTP was detected in both cotyledon and embryonic axes of the seeds. Immunofluorescence assays also indicated that LTP was localized in the cell wall and in cytosolic compartments. In addition the presence of nsLTP was detected in seeds of different cultivars of cowpea and in three other leguminous seeds (Vigna vexillata, Canavalia ensiformis and Phaseolus vulgaris).