Abstract
Plant glutamate-like receptor genes (GLRs) are homologous to mammalian ionotropic glutamate receptors genes (iGluRs). Although GLRs have been implicated in plant defenses to biotic stress, the relationship between GLR-mediated plant immunity against fungal pathogens and electrical signals remains poorly understood. Here, we found that pretreatment with a GLR inhibitor, 6,7-dinitriquinoxaline-2,3-dione (DNQX), increased the susceptibility of tomato plants to the necrotrophic fungal pathogen Botrytis cinerea. Assessment of the glr3.3, glr3.5 and glr3.3/glr3.5 double-mutants upon B. cinerea infection showed that tomato GLR3.3 and GLR3.5 are essential for plant immunity against B. cinerea, wherein GLR3.3 plays the main role. Analysis of the membrane potential changes induced by glutamate (Glu) or glycine (Gly) revealed that amplitude was significantly reduced by knocking out GLR3.3 in tomato. While treatment with Glu or Gly significantly increased immunity against B. cinerea in wild-type plants, this effect was significantly attenuated in glr3.3 mutants. Thus, our data demonstrate that GLR3.3- and GLR3.5-mediated plant immunity against B. cinerea is associated with electrical signals in tomato plants.
Highlights
Plants that grow in a natural environment are continuously threatened by a wide variety of pathogens
We found that GLR3.3 and GLR3.5 are important players in plant immunity against B. cinerea in tomato, possibly through binding to ligand glutamate (Glu) or glycine (Gly), thereby triggering electrical signals
These findings indicate that GLRs positively regulate plant immunity against B. cinerea in tomato plants
Summary
Plants that grow in a natural environment are continuously threatened by a wide variety of pathogens. These biotic stressors affect crop production and often cause economic losses. They have acquired a range of signal-transduction systems during evolution to effectively mitigate the adverse effects of environmental changes. The faster these signals maneuver, the more likely it is that plants will adapt and resist the incoming stress. Plant glutamate-like receptor genes (GLRs) are homologous to mammalian ionotropic glutamate receptors genes (iGluRs), which trigger electrical and Ca2+ signal cascades [3,6]. There are 13 full-length GLR genes in tomato plants [9]
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