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1.  Expression and Biological Activity of the Cystine Knot Bioinsecticide PA1b (Pea Albumin 1 Subunit b) 
PLoS ONE  2013;8(12):e81619.
The PA1b (Pea Albumin 1, subunit b) peptide is an entomotoxin extract from Legume seeds with lethal activity on several insect pests, such as mosquitoes, some aphids and cereal weevils. This 37 amino-acid cysteine-rich peptide has been, until now, obtained by biochemical purification or chemical synthesis. In this paper, we present our results for the transient production of the peptide in Nicotiana benthamiana by agro-infiltration, with a yield of about 35 µg/g of fresh leaves and maximum production 8 days after infiltration. PA1b is part of the PA1 gene which, after post-translational modifications, encodes two peptides (PA1b and PA1a). We show that transforming tobacco with the PA1b cDNA alone does not result in production of the toxin and, in fact, the entire cDNA is necessary, raising the question of the role of PA1a. We constructed a PA1-cassette, allowing for the quick “cut/paste” of different PA1b mutants within a conserved PA1 cDNA. This cassette enabled us to produce the six isoforms of PA1b which exist in pea seeds. Biological tests revealed that all the isoforms display similar activity, with the exception of one which is inactive. The lack of activity in this isoform led us to conclude that the amphiphilic nature of the peptide is necessary for activity. The possible applications of this expression system for other cysteine-rich biomolecules are discussed.
doi:10.1371/journal.pone.0081619
PMCID: PMC3859497  PMID: 24349099
2.  High toxicity and specificity of the saponin 3-GlcA-28-AraRhaxyl-medicagenate, from Medicago truncatula seeds, for Sitophilus oryzae 
BMC Chemical Biology  2012;12:3.
Background
Because of the increasingly concern of consumers and public policy about problems for environment and for public health due to chemical pesticides, the search for molecules more safe is currently of great importance. Particularly, plants are able to fight the pathogens as insects, bacteria or fungi; so that plants could represent a valuable source of new molecules.
Results
It was observed that Medicago truncatula seed flour displayed a strong toxic activity towards the adults of the rice weevil Sitophilus oryzae (Coleoptera), a major pest of stored cereals. The molecule responsible for toxicity was purified, by solvent extraction and HPLC, and identified as a saponin, namely 3-GlcA-28-AraRhaxyl-medicagenate. Saponins are detergents, and the CMC of this molecule was found to be 0.65 mg per mL. Neither the worm Caenorhabditis elegans nor the bacteria E. coli were found to be sensitive to this saponin, but growth of the yeast Saccharomyces cerevisiae was inhibited at concentrations higher than 100 μg per mL. The purified molecule is toxic for the adults of the rice weevils at concentrations down to 100 μg per g of food, but this does not apply to the others insects tested, including the coleopteran Tribolium castaneum and the Sf9 insect cultured cells.
Conclusions
This specificity for the weevil led us to investigate this saponin potential for pest control and to propose the hypothesis that this saponin has a specific mode of action, rather than acting via its non-specific detergent properties.
doi:10.1186/1472-6769-12-3
PMCID: PMC3388004  PMID: 22536832
Saponin; Insect; Medicago truncatula; Sitophilus oryzae
3.  Pea Albumin 1 Subunit b (PA1b), a Promising Bioinsecticide of Plant Origin 
Toxins  2011;3(12):1502-1517.
PA1b (Pea Albumin 1, subunit b) is a peptide extract from pea seeds showing significant insecticidal activity against certain insects, such as cereal weevils (genus Sitophilus), the mosquitoes Culex pipiens and Aedes aegyptii, and certain species of aphids. PA1b has great potential for use on an industrial scale and for use in organic farming: it is extracted from a common plant; it is a peptide (and therefore suitable for transgenic applications); it can withstand many steps of extraction and purification without losing its activity; and it is present in a seed regularly consumed by humans and mammals without any known toxicity or allergenicity. The potential of this peptide to limit pest damage has stimulated research concerning its host range, its mechanism of action, its three-dimensional structure, the natural diversity of PA1b and its structure-function relationships.
doi:10.3390/toxins3121502
PMCID: PMC3268454  PMID: 22295174
PA1b; insect; bioinsecticide; Legumes

Results 1-3 (3)