Effect of glutamate on Pyricularia oryzae infection of rice monitored by changes in photosynthetic parameters and antioxidant metabolism

Abstract

Considering the importance of blast caused by Pyricularia oryzae in the decrease of rice yield worldwide, this study aimed to assess the photosynthetic performance [leaf gas exchange and chlorophyll (Chl) a fluorescence parameters as well as the photosynthetic pigments concentration], the activities of antioxidant enzymes [ascorbate peroxidase, catalase (CAT), peroxidase (POX), superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione reductase (GR) and glutathione‐S‐transferase] and concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in the leaves of rice plants non‐supplied (−Glu) or supplied (+Glu) with glutamate (Glu) and non‐infected or infected by P. oryzae. Blast severity was reduced in the leaves of +Glu plants. On the infected leaves of +Glu plants, the values for internal CO2 concentration were lower while the values for net carbon assimilation rate, stomatal conductance as well as for the concentrations of Chl a, Chl b and carotenoids were higher in comparison to infected leaves of −Glu plants. The functionality of the photosynthetic apparatus was preserved in the infected leaves of +Glu plants. The activities of CAT, GPX, GR, POX and SOD increased in the infected leaves of both −Glu and +Glu plants compared to their non‐inoculated counterparts, but their activities were lower for +Glu plants. The lower activity of these antioxidative enzymes was triggered by the reduced hydrogen peroxide concentration in the infected leaves of +Glu plants resulting in lower MDA concentration. It can be concluded that photosynthesis was less impaired in infected plants supplied with glutamate due to the lower biochemical constraints for CO2 fixation. Moreover, there was a need for lower activity of reactive oxygen species scavenging enzymes in infected leaves of plants supplied with glutamate due to the lower oxidative stress imposed by P. oryzae infection.

Overexpression of ATP Synthase Subunit Beta (Atp2) Confers Enhanced Blast Disease Resistance in Transgenic Rice

“…According to various related studies, one of the important indicators of stress tolerance in rice is chlorophyll a and chlorophyll b [41], and infection by the rice blast fungus can lower the ratio of chlorophyll a to chlorophyll b content in the grain [42]. In the present study, Atp2 maintained the stability of chlorophyll synthesis in the transgenic plants, possibly improving the resistance of the rice plants to the rice blast fungus.…”

Physiological and Biochemical Aspects of Silicon-Mediated Resistance in Maize against Maydis Leaf Blight

“…The homogenate was centrifuged at 10,000× g for 15 min at 4 °C. The supernatant was used to determine H 2 O 2 concentration following the procedures of Dias et al [ 64 ]. Leaf tissue (100 mg) was ground as described above and the fine powder was homogenized in 1 mL of a solution containing 100 mM potassium phosphate buffer (pH 7.2) and 1 mM sodium diethyldithiocarbamate.…”

“…Leaf tissue (100 mg) was ground as described above and homogenized in 2 mL of 0.1% (w/v) trichloroacetic acid solution and the homogenate was centrifuged at 12,000× g for 15 min at 4 • C. After centrifugation, 250 µL of the supernatant was added to 750 µL of thiobarbituric acid solution and homogenized in a thermomixer for 30 min at 95 • C. The samples were centrifuged at 9000× g for 10 min and the absorbances were obtained at 600 and 532 nm [63] •− Concentrations Leaf tissue (100 mg) was ground as described above and homogenized in 1 mL of a mixture containing 50 mM potassium phosphate buffer (pH 6.5) and 1 mM hydroxylamine. The homogenate was centrifuged at 10,000× g for 15 min at 4 • C. The supernatant was used to determine H 2 O 2 concentration following the procedures of Dias et al [64]. Leaf tissue (100 mg) was ground as described above and the fine powder was homogenized in 1 mL of a solution containing 100 mM potassium phosphate buffer (pH 7.2) and 1 mM sodium diethyldithiocarbamate.…”