Variability of the inhibitors of serine, cysteine proteinases and insect α-amylases in Vigna and Phaseolus

Abstract

Inhibitor polymorphism was studied, in the seeds of 93 accessions of 24 species in the 7 subgenera of Vigna and 55 accessions of 14 Phaseolus species, by isoelectric focusing combined with the gelatine replicas method. The majority of species examined have species specific spectra for trypsin and chymotrypsin inhibitors (TIs and CIs). In addition, considerable intraspecific variability was detected for TIs and CIs in most species, for example, V angularis, V. radiata and V hirtella. However, intraspecific variability for TIs and CIs was very low in, for example, V. minima and V. mungo. Inter- population variation for TIs and CIs were detected in V angularis var. nipponensis from Japan. In some accessions single seeds differed by TIs (e.g. in V. adenantha). Differences were found in spectra of TIs and CIs from seeds and leaves of the same accession of Vigna. Leaf TIs and CIs also differed between Vigna species. Inhibitor spectra of the microbial proteinase subtilisin (Sis) from seeds were less complex and less variable than TIs. Spectra of SIs were specific for species and groups of species within Vigna and Phaseolus. Cysteine proteinase (papain-like) inhibitors (CPIs) generally show variation at the species level in both Vigna and Phaseolus. Inhibitors of diploid V trinerva were closer to those of the tetraploid V. glabrescens than other species. Active and polymorphic insect alpha-amylase inhibitors (Als) were found only in Phaseolus species not Vigna. The research results indicate that for Vigna and Phaseolus TIs and CIs are useful for analysis of diversity from the individual to the species level, SIs and CPIs are more useful for analysis of diversity at the species level and Als are only useful for studying variation in Phaseolus. Variation revealed in this study could be useful in relation to breeding legumes for pathogen and pest resistance.