ISSN 1021-4437, Russian Journal of Plant Physiology, 2016, Vol. 63, No. 5, pp. 609–619. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © S.V. Veselova, G.F. Burkhanova, T.V. Nuzhnaya, I.V. Maksimov, 2016, published in Fiziologiya Rastenii, 2016, Vol. 63, No. 5, pp. 649–660.
Roles of Ethylene and Cytokinins in Development of Defense Responses
in Triticum aestivum Plants Infected with Septoria nodorum
S. V. Veselova, G. F. Burkhanova, T. V. Nuzhnaya, and I. V. Maksimov
Institute of Biochemistry and Genetics, Ufa Scientific Center, Russian Academy of Sciences,
pr. Oktyabrya 71, Ufa, 450054 Bashkortostan, Russia
Received February 2, 2016
Abstract—Effects of ethephon (2-chloroethylphosphonic acid, ET), which is a producer of ethylene, and
1-methylcyclopropene (1-MCP), which inhibits ethylene binding with the corresponding receptors, on
defense responses caused by the causal agent of leaf blotch (Septoria nodorum Berk.) in leaves of soft spring
wheat (Triticum aestivum L.) of cultivars contrast in the resistance to the pathogen were studied. After treat-
ment with 1-MCP, an induction of wheat resistance to the disease, more prominent in the susceptible cv.
Kazakhstanskaya 10 than in the resistant cv. Omskaya 35, was found. The rise in the resistance was accom-
panied by rise in zeatin content in leaves, enhanced generation of hydrogen peroxide (most likely, due to the
decreased catalase activity and increased peroxidase activity), and accumulation of transcripts of marker
genes of the salicylate signaling pathway (PR-1 and PR-2). On the contrary, in ET-treated plants, all the stud-
ied defense responses were inhibited, and the pathogen developed more intensively. The effect of ethylene on
zeatin distribution in infected wheat leaves of the susceptible cv. Kazakhstanskaya 10 was also found. In the
1-MCP-treated wheat leaves, cytokinins were localized in mesophyll cells and cell walls. In the ET-treated
leaves, cell walls were free of zeatin, and the hormone concentrated in developing hyphae of the pathogen.
The results allow for the hypothesis that wheat plant resistance is controlled by antagonistic interaction of sig-
naling pathways of salicylic acid and ethylene with participation of cytokinins.
Keywords: Triticum aestivum, Septoria nodorum, cytokinins, ethylene, hydrogen peroxide, immunolocaliza-
tion, PR proteins, resistance
Deployment of defense reactions in response to
biotic stressors in many respects depends on plant abil-
ity to produce various hormones and signal molecules
playing key roles in induction of systemic resistance
against phytopathogens . It is shown that ROS pro-
duction is the earliest response of plants to infections, it
is an important element in establishment of systemic
resistance, and it is controlled by enzymes of pro-/anti-
oxidant system and phytohormones [2, 3]. In addition,
development of systemic resistance is associated with
syntheses of defensive PR proteins [2, 4].
It was revealed that infected plants, in order to
effectively protect themselves, activate simultaneous
or sequential hormonal signaling systems having com-
plex synergistic or antagonistic interactions with each
other [5, 6]. For example, plant immunity is regulated,
to a large extent, by salicylic (SA) and jasmonic (JA)
acids, as well as ethylene [1, 5]. It is recognized that
the SA-induced resistance targets biotrophic and
hemibiotrophic pathogens [1, 5]. Meanwhile, ethy-
lene in cooperation with JA renders plant resistant to
necrotrophs and pests [1, 3]. However, some works
show that ethylene may attenuate an immune poten-
tial against some pathogens, including those exhibit-
ing necrotrophic and hemibiotrophic characteristics
[1, 5, 7]. Thus, ethylene may be both an up- and
down-modulator of resistance depending on a patho-
gen type and environmental conditions . This pro-
vides a basis for the hypotheses of ethylene importance
in a control of SA-dependent and JA- dependent
defense responses .
However, plant immunity is governed not only by
SA, JA, and ethylene but also by the whole phytohor-
monal complex, including cytokinins (CKs) [6, 8, 9].
The latter may contribute to the resistance formation
through regulation of SA-dependent defense
responses, induction of gene expression of defensive
proteins, phytoalexin synthesis, and lignification pro-
cesses [6, 8, 10]. Unfortunately, molecular mecha-
nisms of CK interactions with other phytohormones,
Abbreviations: CAT—catalase; CK—cytokinin; ET—ethephon;
—hydrogen peroxide; JA—jasmoniс acid; Kaz10—
Kazakhstanskaya 10; 1-MCP—1-methylcyclopropene; Om35—
Omskaya 35; PO—peroxidase; PB—Na-phosphate buffer; PR
proteins—pathogenesis-related proteins; SA—salicylic acid.