Allelic differentiation of Kunitz trypsin inhibitor in wild soybean (Glycine soja)

Defense response in non-genomic model species: methyl jasmonate exposure reveals the passion fruit leaves' ability to assemble a cocktail of functionally diversified Kunitz-type trypsin inhibitors and recruit two of them against papain

Multiplicity of protease inhibitors induced by predators may increase the understanding of a plant's intelligent behavior toward environmental challenges. Information about defense mechanisms of non-genomic model plant passion fruit (Passiflora edulis Sims) in response to predator attack is still limited. Here, via biochemical approaches, we showed its flexibility to build-up a broad repertoire of potent Kunitz-type trypsin inhibitors (KTIs) in response to methyl jasmonate. Seven inhibitors (20-25 kDa) were purified from exposed leaves by chromatographic techniques. Interestingly, the KTIs possessed truncated Kunitz motif in their N-terminus and some of them also presented non-consensus residues. Gelatin-Native-PAGE established multiple isoforms for each inhibitor. Significant differences regarding inhibitors' activity toward trypsin and chymotrypsin were observed, indicating functional polymorphism. Despite its rarity, two of them also inhibited papain, and such bifunctionality suggests a recruiting process onto another mechanistic class of target protease (cysteine-type). All inhibitors acted strongly on midgut proteases from sugarcane borer, Diatraea saccharalis (a lepidopteran insect) while in vivo assays supported their insecticide properties. Moreover, the bifunctional inhibitors displayed activity toward midgut proteases from cowpea weevil, Callosobruchus maculatus (a coleopteran insect). Unexpectedly, all inhibitors were highly effective against midgut proteases from Aedes aegypti a dipteran insect (vector of neglected tropical diseases) opening new avenues for plant-derived PIs for vector control-oriented research. Our results reflect the KTIs' complexities in passion fruit which could be wisely exploited by influencing plant defense conditions. Therefore, the potential of passion fruit as source of bioactive compounds with diversified biotechnological application was strengthened.

Proteomic characterization of Kunitz trypsin inhibitor variants, Tia and Tib, in soybean [Glycine max (L.) Merrill]

The soybean Kunitz trypsin inhibitor (KTi) has several polymorphic variants. Of these, Tia and Tib, which differ by nine amino acids, are the two main types. In this study, differences in KTi proteome between Tia and Tib were investigated using three soybean cultivars and three mutant lines. Two cultivars, Baekwoon (BW) and Paldal (PD), and one mutant line, SW115-24, were Tia type, whereas one soybean cultivar, Suwon115 (SW115), and two mutant lines, BW-7-2 and PD-5-10, were Tib type. Protein from the six soybean lines was extracted and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), non-denaturing polyacrylamide gel electrophoresis (non-denaturing PAGE), and two-dimensional polyacrylamide gel electrophoresis (2-DE). By SDS-PAGE, there was no difference between soybean cultivars and mutant lines, except for SW115-24. Western blot analysis revealed that, in comparison with Tia, Tib type accumulated relatively low amounts of KTi. By non-denaturing PAGE, the three soybean lines of Tib type were characterized by slower mobility than the three soybean lines of Tia type. Zymography detected eight distinct zones of trypsin inhibitory activity among which Tia and Tib lacked the fifth and sixth zone, respectively. By two-dimensional native polyacrylamide gel electrophoresis (2-DN), the spots related to trypsin inhibitory activity showed different mobilities, whereas only one KTi (21.5 kDa) spot was resolved by 2-DE. By two-dimensional zymography (2-DZ), Tib showed a broader activity zone (pI 4-7) in comparison with Tia (pI 4-5). The results indicate that the genotypes with a different type of KTi present different proteomic profiles and trypsin inhibitory activities.

Identification of Kunitz trypsin inhibitor mutations using SNAP markers in soybean mutant lines

The Kunitz trypsin inhibitor (KTi) in soybean has several polymorphic types that are controlled by multiple alleles, which behave in a co-dominant fashion. Of these, Tia and Tib, which differ by nine amino acids, are the predominant types. In order to develop a single nucleotide amplified polymorphism (SNAP) marker for the classification of the predominant KTi types, Tia and Tib, and evaluate KTi activities by differing KTi type total 451 soybean mutant lines (M(12)-M(16) generation) were incorporated in this study. Among 451 soybean mutants, 144 and 13 mutant lines showed decreased and increased trypsin inhibitor activity when compared with the original cultivars, respectively. To identify the KTi type, we designed a SNAP marker. Among 451 mutant lines from 12 soybean cultivars and landraces, 8 mutant lines derived from cvs. Baekwoon, Paldal and Suwon115 showed a change in KTi type when compared with the original cultivars using the SNAP marker. Five mutant lines in Suwon115 changed from Tib to Tia, while two mutant lines derived from cv. Baekwoon and one mutant line derived from cv. Paldal were changed from Tia to Tib. These changes of KTi types were confirmed by sequencing of the KTi genes and non-denaturing polyacrylamide gel electrophoresis of the KTi proteins. To identify the effect of KTi activity based on the change in KTi type, we measured the KTi activity using the three cultivars and eight mutant lines that showed changes in KTi type. Two mutant lines (BW-1 and 7-2) derived from cv. Baekwoon and one mutant line (PD-5-10) from cv. Paldal that changed from Tia to Tib showed lower activity than the original cultivar. In cv. Suwon115, five mutant lines that changed from Tib to Tia showed higher activity than the original cultivar. These results indicate that the designed SNAP marker was capable of identifying the KTi type and that Tia activity was higher than Tib activity in soybean.