© Benaki Phytopathological Institute
Hellenic Plant Protection Journal
11:
71-77, 2018
DOI 10.2478/hppj-2018-0010
Department of Molecular Biology and Biotechnology,
AECS, P.O.Box 6091 Damascus, Syria
*Corresponding author:
Changes in salicylic acid content and pathogenesis - related
(
PR2
) gene expression during barley -
Pyrenophora teres
interaction
A. Al-Daoude*, M. Jawhar, E. Al-Shehadah, A. Shoaib, M. Orfi and M.I.E Arabi
Summary
Net blotch (NB), caused by the necrotrophic fungal pathogen
Pyrenophora teres f. teres
,
substantially reduces barley grain yield and quality worldwide. The role of salicylic acid (SA) signal-
ing in NB resistance has been poorly documented. In this study, SA levels as well as the expression of
the SA-responsive gene
PR2
were monitored in infected leaves of two barley genotypes, Banteng (re-
sistant) and WI2291 (susceptible), at different time points of infection
.
SA signaling was activated in
bothgenotypes 24 hours post infection (hpi) as compared with non-inoculated plants. However, with
or without pathogen pretreatment, SA significantly increased (P=0.001) in Banteng comparing with
WI2291. RT-PCR analysis revealed that
PR2
expression increases in the resistant and susceptible geno-
types over the inoculation time points, with maximum expression (6.4 and 1.99-fold, respectively) ob-
served 6 dpi
. PR2
expression was paralleled by an increase in leaf SA content as shown by the test co-
incidence (F
3, 32
= 4.74,
P
= 0.001). Based on barley genotype resistance levels, our data strengthen the
idea that SA signaling and
PR2
play a role in barley NB reduction.
Additional keywords:
barley,
Pyrenophora teres
,
PR2
gene expression, RT-PCR, salicylic acid
modes of action in physiological processes
could help in the dissection of the SA signal-
ing network, confirming its important role in
plant responses to fungal diseases (
Vásquez
et al.,
2015). After a pathogen attack SA lev-
els often increase and lead to the induction
of PR expression and the development of
systemic acquired resistance and hypersen-
sitive response. Furthermore, SA appears to
regulate the delicate balance between pro-
and after- cell death functions during hyper-
sensitive response (Dorey
et al.,
1997; Alvar-
ez, 2000).
Barley plants produce enzymes that di-
gest fungal cell walls to stop fungal pene-
tration. However, since all true fungi contain
chitin as a primary structural component
of their cell walls, the chitinase family of PR
proteins is of particular importance
(
Wes-
sels, 1994). Chitin in fungal cell walls can be
hydrolyzed by chitinases into smaller oli-
gomers or monomers
(
Bishop
et al.,
2002),
so PR proteins such as
PR2
are known to play
a major role during plant–pathogenic fun-
gus interactions (Collinge
et al.,
1993; Dangl
and Jones, 2001).
Quantitative PCR (qPCR) is now a well-
Introduction
Net blotch, caused by the fungal patho-
gen
Pyrenophora Drechs. teres
Smedeg. (an-
amorph:
Drechslera teres
[Sacc.] Shoem. f.
Teres
Smedeg.), is a common foliar disease
of barley (
Hordeum vulgare
L.), a disease re-
sponsible for heavy crop losses (
Liu
et al.,
2011
;
Wang
et al.,
2015
). Various mechanisms
for NB resistance and susceptibility appear
to operate in barley.
Pyrenophora teres
acti-
vates different defense responses which are
regulated through different plant signaling
pathways, including plant hormones such
as SA and pathogenesis-related (PR) pro-
teins (Wang
et al.,
2011; Bogacki
et al.,
2008).
A number of studies have demonstrat-
ed that SA signaling pathways play impor-
tant roles in resistance against fungal patho-
gens in plants (Trusov
et al.,
2009; Zwart
et
al.,
2017). Therefore, discovery of SA targets
and the understanding of their molecular
