ISSN 1021-4437, Russian Journal of Plant Physiology, 2006, Vol. 53, No. 4, pp. 488–494. © MAIK “Nauka /Interperiodica” (Russia), 2006.
Original Russian Text © O.L. Ozeretskovskaya, N.I. Vasyukova, Ya.S. Panina, G.I. Chalenko, 2006, published in Fiziologiya Rastenii, 2006, Vol. 53, No. 4, pp. 546–553.
One of the hot problems of current agriculture is
plant defense against pathogens and pests, which cause
an annual loss of 15 to 30% of yield. Until now, plant
treatment with pesticides is a basic way of plant
defense. However, pesticides not only kill their targets,
pathogenic organisms, but also damage the surrounding
beneﬁcial microﬂora. Some pesticides are known to
display site-speciﬁcity, and modiﬁcation of a sensitive
site might result in the accumulation of resistant patho-
gen forms in their population .
Currently, researchers attempt to reduce pesticide
application, replacing it by using other defense meth-
ods based on the increase in plant resistance . The
most well-known among them is the application of elic-
itors. Elicitors are biogenic or abiogenic compounds;
their action is directed not to parasite elimination but to
induction of organism defense properties. After treat-
ment with elicitors, plants acquire resistance to a wide
range of pathogens, i.e., unspeciﬁc resistance .
However, even the usage of efﬁcient elicitor and its
competent application do not ensure successful elicita-
tion. This might be related to the presence in the patho-
gens of suppressors, which action is opposite to that of
elicitors, i.e., compounds inducing an increased suscep-
tibility of plant tissues to diseases .
The mechanisms of elicitor action are currently
under intense investigation , whereas suppressor
action is almost unstudied. Since these compound
actions are opposite to this of elicitors, a comparison of
their action mechanisms is of a great interest.
One of the contributors to the signal system forma-
tion responsible for resistance development is salicylic
acid (SA), which is synthesized in plants and accumu-
lates in the loci of resistance formation [4, 5]. In plant
tissues, SA can be in free or bound form with a predom-
-D-glucoside among the latter. Free SA is
capable of resistance induction. Bound SA does not
possess such capability, but it is a store of SA in tissues
[6, 7]. The role of SA in immunosuppression is unclear.
The objective of this work was a comparison of elic-
itor and suppressor actions on resistance and suscepti-
bility of potato plants to the causal agent of late blight.
Such investigation seemed rather interesting because it
permitted a comparison of the signaling pathways of
elicitation and immunosuppression of potato tubers
Effect of Immunomodulators on Potato Resistance
and Susceptibility to
O. L. Ozeretskovskaya, N. I. Vasyukova, Ya. S. Panina, and G. I. Chalenko
Bach Institute of Biochemistry, Russian Academy of Sciences, Leninskii pr. 33, Moscow, 119071 Russia;
fax: 7 (495) 954-2732; e-mail: firstname.lastname@example.org
Received October 25, 2005
—The mechanisms of induced resistance and susceptibility of potato (
to late blight agent (
Mont de Bary) were studied using an elicitor chitosan and an immu-
nosuppressor laminarin. It was elucidated that treatment of disks from potato tubers with chitosan resulted in
salicylic acid (SA) accumulation due to activation of benzoate-2-hydroxylase and hydrolysis of SA conjugates.
Such SA accumulation in potato tissues inhibited one of the antioxidant enzymes, catalase, inducing an oxida-
tive burst and resistance development. The mechanisms of induced susceptibility to the late blight causal agent
were studied using an unspeciﬁc immunosuppressor, laminarin, an analogue of natural speciﬁc suppressor of
potato immune responses,
-glucan. It was established that the development of immunosuppression
in tissues treated with laminarin did not affect the SA level in tissues. However, catalase sensitivity to SA
reduced in laminarin-treated tissues, and the enzyme activity increased. In its turn, this might result in the
reduced level of hydrogen peroxide in the cells and, as a sequence, in the increased potato susceptibility to late
Key words: Solanum tuberosum - Phytophthora infestans - induced resistance - induced susceptibility - chito-
san - laminarin - salicylic acid - catalase - benzoate-2-hydroxylase
: AT—3-amino-1,2,4-triazole; BA—benzoic acid;
BA-2-H—benzoate-2-hydroxylase; SA—salicylic acid; DMTU—
1,3-dimethylthiourea; DPI—diphenyleneiodoniumchloride; ROS—
reactive oxygen species; TEA—Tris-ethanol-amine.