Stimulation of defense reactions in Medicago truncatula by antagonistic lipopeptides from Paenibacillus sp. strain B2

With the aim of obtaining new strategies to control plant diseases, we investigated the ability of antagonistic lipopolypeptides (paenimyxin) from Paenibacillus sp. strain B2 to elicit hydrogen peroxide (H₂O₂) production and several defense-related genes in the model legume Medicago truncatula. For this purpose, M. truncatula cell suspensions were used and a pathosystem between M. truncatula and Fusarium acuminatum was established. In M. truncatula cell cultures, the induction of H₂O₂ reached a maximum 20 min after elicitation with paenimyxin, whereas concentrations higher than 20 μM inhibited H₂O₂ induction and this was correlated with a lethal effect. In plant roots incubated with different concentrations of paenimyxin for 24 h before inoculation with F. acuminatum, paenimyxin at a low concentration (ca. 1 μM) had a protective effect and suppressed 95% of the necrotic symptoms, whereas a concentration higher than 10 μM had an inhibitory effect on plant growth. Gene responses were quantified in M. truncatula by semiquantitative reverse transcription-PCR (RT-PCR). Genes involved in the biosynthesis of phytoalexins (phenylalanine ammonia-lyase, chalcone synthase, chalcone reductase), antifungal activity (pathogenesis-related proteins, chitinase), or cell wall (invertase) were highly upregulated in roots or cells after paenimyxin treatment. The mechanisms potentially involved in plant protection are discussed.

[Effect of Paenibacillus polymyxa lectin on cytokine status of animals]

AIM

To study effect of lectin L II of Paenibacillus polymyxa 1460 on cytokine status of mice during modeling of infections caused by Staphylococcus, Escherichia and Yersinia.

MATERIALS AND METHODS

Lectin LII of P. polymyxa 1460, bacterial cultures Staphylococcus aureus 209-P, Escherichia coli O1, and Yersinia enterocolitica 12 were used. Mice were inoculated intraperitoneally with 0.2 ml of suspension of bacterial culture grown during 24 hours (5,000 m.c./ml). Lectin (0.4 mcg/ml) in dose 0.2 ml was administered 24 h before and 1 h after inoculation. Serum samplesfrom sacrificed animals were obtained 1, 6, and 24 hours after inoculation and concentrations of IL-1, IL-6, and TNF-alpha were measured in them using optical density values.

RESULTS

It was established that level of TNF-alpha in serum decreased during staphylococcal infection, whereas levels of IL-1 and IL-6 decreased during all modeled infections. Ability for correction of cytokine balance in organism of experimental animals by administration of lectin 24 h before and 1 h after inoculation with bacteria was demonstrated.

CONCLUSION

Presented studies testify to the effect of bacterial lectin on cytokine-production activity of macrophages during phagocytosis of bacteria and infectious process.