Host range of the potential biopesticide Pea Albumin 1b (PA1b) is limited to insects

The interaction of the bioinsecticide PA1b (Pea Albumin 1 subunit b) with the insect V-ATPase triggers apoptosis

“…This conclusion is supported by the results of PA1b toxicity tests realized on Sf9 cells 24 from the caterpillar Spodoptera frugiperda . The Sf9 cells were found to be sensitive to PA1b, but living whole insects appeared to be insensitive to the peptide 6 . Considering that the affinity for V-ATPase is quite similar in sensitive and insensitive insect species 5, 11 , the insensitivity must be due to an, as yet, unidentified mechanism, and one which is very different from the mechanism of “true” resistance observed in resistant weevil ISOR3 due to an absence of binding between the PA1b toxin and the V-ATPase.…”

“…Since its host range is limited to insects 6 , it can be considered safe for mammals and other non-target organisms which may be in contact with PA1b during its use as a pesticide. However, before applying this new plant pesticide on an industrial scale, it is important to understand its mechanism of action.…”

“…PA1b is an entomotoxin extracted from pea seeds and, more generally, from Legume seeds 3 . PA1b is active orally and it displays outstanding insecticidal activity against certain insects, such as cereal weevils (genus Sitophilus ) and mosquitoes 4–6 . PA1b was first discovered in 1986 and consists of 37 amino acids, including six cysteines involved in three intramolecular disulfide bridges 7 .…”

“…However, nothing is known about the triggering of apoptosis after the inhibition of V-ATPase in whole insects. Three situations occur in whole insects upon Pa1b intoxication: (i) insects, such as the Sitophilus oryzae strain WAA42, are sensitive to the toxin and PA1b-I 125 binds to their V-ATPase receptors; (ii) insects, such as the Sitophilus oryzae strain ISOR3, are totally resistant to the toxin due to the non-interaction with V-ATPase; and (iii) insects, such as the red flour beetle Tribolium castaneum , were found to be insensitive although the PA1b-I 125 binding site exists on extracts from this insect, with characteristics similar to those of the sensitive insects 5, 6 . These three insect models, the sensitive S. oryzae strain WAA42, the resistant S. oryzae strain ISOR3 and the insensitive T. castaneum , were used in biochemical and histological experiments to demonstrate that a PA1b/V-ATPase interaction triggers the apoptosis mechanism, resulting in insect death.…”

Clitoria ternatea (butterfly pea) cyclotides: insights on functional diversity, regulation and biotechnological applications

“…PA1b also adopts a cystine-knot topology which makes it resistant to trypsin digestion and renders it thermostable at 120⁰C for 15 mins [54]. Like cyclotides, the PA1b peptide is reported to have insecticidal activities [54][55][56][57]. However, unlike cyclotides where their bioactivity is due to membrane disruption, the insecticidal activity of PA1b is primarily attributed to its ability to inhibit the vacuolar-ATPase (V-ATPase) in the plasma membrane [55,57].…”