© Benaki Phytopathological Institute
Salicylic acid expression at barley–
Pyrenophora teres
interaction
75
encodes for a 1,3-ß-glucanase (Simmons,
1994), belonging to the glycoside hydrolas-
es family (
Opassiri
et al
., 2010
). 1, 3-ß-gluca-
nase hydrolyses the ß-
O-
glycosidic bond of
ß-glucan in plant cell walls, resulting in cell
wall loosening and expansion (
Akiyama
et
al
., 2009
). This phenomenon may be the
cause of barley cell wall leakage during
NB
infestations.
Our data showed that
PR2
gene exhib-
ited a differential expression (
P
=0.01) in the
tolerant and susceptible barley genotypes
and was closely related to the increase of
the SA level. The SA marker
PR2
was upreg-
ulated 3-fold in infected leaves of the toler-
ant Banteng than in the susceptible WI2291
(Fig. 2).
PR2
expression was paralleled by an
increase in leaf salicylic acid (SA) content as
shown by the coincidence test (F
3, 32
= 4.74,
P
= 0.001). This is supported by previous works
indicating that SA is involved in the regula-
tion of induced immunity in barley through
the induction of PR proteins with chitinase,
β-1, 3-glucanase and peroxidase enzyme
activity, both locally and systemically (Bind-
schedler
et al.,
1998).
Our data show that the contribution of
the SA pathway to the resistance response
appears to depend on the plant genotype.
The NB tolerant genotype Banteng used for
this study was proved to be the most resis-
tant genotype to all
P. teres
isolates available
so far. The higher activities of the select-
ed defense genes such as
PR2
and higher
level of SA in infected Banteng leaf tissues
compared with the susceptible genotype
WI 2291 may explain its high level of resis-
tance.
This study provides information about
the role of SA in resistance of barley against
the necrotrophic foliar pathogen
P. teres.
In
addition, it highlights that SA may increase
in response to
P. teres
infection in different
barley genotypes. It is also noteworthy that
PR2
has a higher constitutive expression and
faster induction in the tolerant genotype as
compared with the susceptible one. Our re-
sults suggested that not only SA is important
for the induction of defense-like responses
but, in the absence of pathogen attack, SA
may sustain basal expression levels of genes
associated with resistance responses and
may keep the defense system primed.
The authors thank the Director General of
AECS and the Head of Biotechnology Depart-
ment for their help throughout the period of
this research.
Literature cited
Abu Qamar, M., Liu, Z. H., Faris, J. D., Chao, S., Ed-
wards, M. C., Lai, Z., Franckowiak, J.D. and Fri-
esen,· T.L. 2008. A region of barley chromosome
6H harbors multiple major genes associated
with the net type net blotch resistance.
Theoret-
ical and Applied Genetics,
117: 1261–1270.
Akiyama, T., Jin, S., Yoshida, M., Hoshino, T., Opas-
siri, R. and Cairns, J.R.K. 2009. Expression of an
endo-(1,3;1,4)-beta-glucanase in response to
wounding, methyl jasmonate, abscisic acid and
ethephon in rice seedlings.
Journal of Plant Phys-
iology,
166: 1814-1825.
Figure 3.
Relative expression profiles of
PR2
gene in the re-
sistant cv. Banteng and in the susceptible cv. WI2291, 24, 48,
72 and 96 hours after infection by
Pyrenophora teres
.
