Bacterial lipopeptides as elicitors of plant defence
W.P. Luzuriaga, L. Franzil, M-L. Fauconnier, M. Deleu, L. Lins, M. Ongena & M.N.
Nasir*
Attention on beneficial plant microorganisms (BCA) has increased in last years as an eco-friendly alternative in crop protection. At
this point, the BCA Bacillus subtilis is interesting because of its capacity to induce a long-term « vaccination effect » (ISR) in the
host plant. Previous works showed that the most efficient ISR elicitor of Bacillus sp. is surfactin (SF), a lipopeptide with high affinity
for the plant plasma membrane (PPM).
Gembloux Agro-Bio Tech, University of Liege. 5030 Gembloux, Belgium
*Corresponding author: Dr. Mehmet Nail NASIR,
mn.nasir@ulg.ac.be.
W.P.L., L.F. and M.N.N. are working for the ARC-FIELD project supported by the Wallonia-Brussels Federation. M.D. and L.L. thank the F.R.S.-F.N.R.S. (National Funds for Scientific Research, Belgium) for their positions as Research Associate and Senior Research Associate, respectively. The authors thank to Mary … and Justine … for their excellent technical support
1200 1210 1220 1230 1240 1250 1260 1270 0 0 0 0 0 0 0 0 PLPC SF-PLPC 1100 1150 1200 1250 1300 1350 0 0.05 0.1 0.15 0.2 0.25 Wavelenght cm-1 A b s o rb an c e
There is an increase of free P=O groups, involvement of phosphate groups in SF-PLPC interactions
2nd derivative 1710 1715 1720 1725 1730 1735 1740 1745 1750 1755 1760 -0.01 0 0 0 0 0 0 0 0 0 PLPC SF-PLPC 1690 1700 1710 1720 1730 1740 1750 1760 1770 0 0.05 0.1 0.15 0.2 0.25 0.3 Wavelenght cm-1 A b s o rb a n c e 2nd derivative
There is an increase of free C=O esther groups, in SF-PLPC interactions 2900 2905 2910 2915 2920 2925 2930 2935 2940 2945 -0.02 -0.01 -0.01 0 0.01 0.01 PLPC SF-PLPC 2750 2800 2850 2900 2950 3000 3050 -0.1 0 0.1 0.2 0.3 0.4 0.5 PLPC SF-PLPC Wavelenght cm-1 A b s o rb a n c e 2nd derivative
There is a shift in CH2 alkyl groups
PLPC is the major phospholipid of plant plasma membrane (PPM), representing more than 40% of the total lipidic composition of PPM. Therefore, a first approach consists in verify the interactions between PLPC and SF.
CH2 group Phosphate group
C=O esther group
0 50 100 150 200 250 300 0 5 10 15 20 25 30 35 40 45 50 100% 90% 50% 30% 20% 10%
Molecular area (Ų/molecule)
S u rf a c e p re s s u re ( m N /m ) PLPC percentage
Langmuir isotherms showing differents percentages of PLPC-SF The interaction SF-PLPC is observed from 30%
surfactin concentration 0 20 40 60 80 100 25 45 65 85 105 125 145 165 185 205 225 Surface pressure = 10 (mN/m) Surface pressure = 30 (mN/m) Surfactin percentage M o le c u la r a re a ( Å ²/ m o le c u le )
Henry et al. 2011. Cellular Microbiology 13: 1824-1837
1: fatty acid chain 2: peptidic ring 3: polar groups
4: hydrophobic residue
Chemical structure of Surfactin (SF)
Plant plasma
membrane
DMSO (control) SF 0 100 200 300 400 500 600 700 800 900 1000 R e la ti v e i n te n s it y 0 2 4 6 8 10 0 200 400 600 800 DMSO Surfac-tine Time (min) R e la ti v e i n te n s it yFluorescence in tobacco cells. Cells were previously loaded with the oxidant-sensing probe DCFH-DA.
Highest fluorescence was observed 5 minutes after
treatment
Tobacco cells in suspension were treated with a solution of SF in DMSO. SF interacts with the PPM and promotes the production of H2O2, an early mechanism of defence in plants.
