The role of a cytosolic superoxide dismutase in barley–pathogen interactions

Abstract

Reactive oxygen species (ROS), including superoxide ( O2·-/ HO2·) and hydrogen peroxide (H O ), are differentially produced during resistance responses to biotrophic pathogens and during susceptible responses to necrotrophic and hemi-biotrophic pathogens. Superoxide dismutase (SOD) is responsible for the catalysis of the dismutation of O2·-/ HO2· to H O , regulating the redox status of plant cells. Increased SOD activity has been correlated previously with resistance in barley to the hemi-biotrophic pathogen Pyrenophora teres f. teres (Ptt, the causal agent of the net form of net blotch disease), but the role of individual isoforms of SOD has not been studied. A cytosolic CuZnSOD, HvCSD1, was isolated from barley and characterized as being expressed in tissue from different developmental stages. HvCSD1 was up-regulated during the interaction with Ptt and to a greater extent during the resistance response. Net blotch disease symptoms and fungal growth were not as pronounced in transgenic HvCSD1 knockdown lines in a susceptible background (cv. Golden Promise), when compared with wild-type plants, suggesting that cytosolic O2·-/ HO2· contributes to the signalling required to induce a defence response to Ptt. There was no effect of HvCSD1 knockdown on infection by the hemi-biotrophic rice blast pathogen Magnaporthe oryzae or the biotrophic powdery mildew pathogen Blumeria graminis f. sp. hordei, but HvCSD1 also played a role in the regulation of lesion development by methyl viologen. Together, these results suggest that HvCSD1 could be important in the maintenance of the cytosolic redox status and in the differential regulation of responses to pathogens with different lifestyles.

The role of reactive oxygen in the development of Ramularia leaf spot disease in barley seedlings

“…The transgenic RNAi line, 161-7-11, has an approx. 4-fold reduction in transcript levels of CSD1 ( Lightfoot et al , 2017 ), whereas the mutant RPr 79/4 has an approx. 90 % reduction in leaf catalase activity ( Kendall et al , 1983 ).…”

“…On the other hand, barley nec1 mutants, which also show reduced RLS symptoms ( McGrann et al , 2015 b ), increased H 2 O 2 levels in response to pathogen inoculation ( Keisa et al , 2011 ). Furthermore, no effect on RLS symptoms was observed in the catalase-deficient mutant RPr 79/4 ( Kendall et al , 1983 ) or the HvCSD1 RNAi line ( Lightfoot et al , 2017 ; Fig. 7 ), both of which have reduced antioxidant levels potentially affecting foliar H 2 O 2 levels.…”

“…Growth inhibition and development of spontaneous necrotic lesions on the leaves were observed under standard glasshouse conditions, but were not visible on RPr 79/4 plants when grown under standard growth room light levels of 220 μmol m –2 s –1 used in the experiments described here. RNA interference (RNAi) line 161–7- 11 has reduced transcript levels of the barley Copper/Zinc superoxide dismutase 1 ( CSD1 ; Lightfoot et al , 2017 ). The Bipolaris sorokiniana tolerant 1 ( bst1 ) mutants have resistance to the spot blotch pathogen Cochliobolus sativus (anamorph Bipolaris sorokiniana ; Persson et al , 2008 , 2009 ).…”

Genome sequence of the potato pathogenic fungus Alternaria solani HWC-168 reveals clues for its conidiation and virulence

“…Surprisingly, a secreted protein exhibiting sequence homology to a superoxide dismutase was identified in the secretome of A. solani HWC-168. It has been reported that the superoxide dismutase is involved in inhibiting oxidative damage of pathogens and plant resistance [ 37 , 38 ]. Furthermore, three trihydrophobins that are commonly found in the surface of aerial hyphae or fruiting body in fungi were predicted to be secreted [ 14 , 15 ].…”

Hydrogen Peroxide Prompted Lignification Affects Pathogenicity of Hemi-biotrophic Pathogen Bipolaris sorokiniana to Wheat

“…In this study there was no significant difference in O 2 − , OH − , and H 2 O 2 before inoculation in resistant and susceptible genotypes, indicating a balanced production, utilization, and scavenging of ROS, under unstressed conditions. After inoculation with B. sorokiniana , O 2 − and OH − levels increased gradually in susceptible genotypes but not resistant ones, in which it eventually started decreasing as the genotypes appeared to balance the oxidative stress by the production of antioxidants such as superoxide dismutase and catalases involved in scavenging free radicals ( Lightfoot et al, 2017 ). This finding supports the idea that resistant genotypes are more successful at detoxifying O 2 − into less harmful substances such as H 2 O 2 , as part of the resistance response.…”