PECULIARITIES MELOIDOOYNE ARACHIDONIC ACID OF FORMING OF RELATIONSHIPS IN INCOGNITA' SYSTEM UNDER THE AND METHYL JASMONATE
SV ZINOVIEVA1, NI VASYUKOVA2,
LI ILIINSKAYA2, EA PEREKHOD2,
NO GERASIMOVA2, GI CHALENKO2 and
1Institute of Parasitology, Russian Academy of Sciences, Moscow 117071, Russia; 2AN Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow 117071, Russia
Background and ojectives
Sterols are known to play a key role in the inter-relation of plants with parasitic nematodes, the latter being auxotrophic organisms in regard to these compounds and compensating for a deficiency in them at the cost of the host . Earlier we found that the natural resistance of tomatoes to Meloidogyne incognita is related to a decrease in the content of free sterols in plants, mainly sigmasterol. The latter is best matched to the nutritional needs of nematodes, resulting in morphogenetic reorganization of the pathogen .
In this work the dependence of resistance of tomatoes to M. incognita on the qualitative and quantitative content of free sterols in tomato plants treated with arachidonic acid (AA) and methyl jasmonate (Me4AA) - singly or in combination - was studied. Me4AA is thought to be an integrated part of the signal transduction system regulating the induction of protection genes in plants, whereas AA is an elicitor of protection reactions.
Materials and methods
The seeds of heterozygous hybrid tomato F Karison are strongly susceptible to M. incognita, and were immersed for 2 h in AA and Me4AA then planted in soil infested by the root-knot nematode. The composition and content of free sterols in the roots was estimated on the 5th day after invasion, and the morphogenetic determination of nematode state was carried out on the 40th day. Plants originating from seeds treated with water were used as control.
Results and conclusions
The content of free sterols in tomato plant roots originating from seeds treated with AA concentrations of 10-7-10-6 M decreased twice compared with control. The content of sigmasterol decreased three-fold (40% of the total amount of sterols versus 70% in control plants). The fecundity of nematodes in tomato roots treated with AA appeared to be 2-4 times lower and its number 2-2.5 times lower than in control. An AA concentration of 10-10 M did not exhibit any activity at all. The treatment of tomato seeds with Me-JAA at 10-6 M did not cause changes in composition and content of sterols and thereby immunostimulation effect in plants.
The mixture of AA and Me-JAA (10-10 and 10-6 M, respectively) significantly enhanced the earlier protective properties of the single AA, the active concentration of AA being a factor of l03 lower than that using pure AA without Me4AA.
The data obtained suggest that the mechanisms of AA-induced and natural tomato resistance to the nematode have the same origin. In both cases the resistance is caused by a deficiency in phytosterols, vitally important for pathogens. The decrease of inducing concentration of AA by a factor of 103 as a result of its mixture with MeJAA is probably caused by an acceleration of signal transduction from elicitor action to expression of protective genes.
1. Bolla R, 1979. Journal of Nematology 11, 250-259.
2. Zinovieva SV, Vasyukova NI, Ozeretskovskaya OL, 1990. Helminthologia 27, 211-216.