Ionotropic glutamate receptors (iGluRs) are ligand-gated cation channels that mediate fast excitatory neurotransmission in the mammalian central nervous system. In the model plant Arabidopsis thaliana, a family of 20 glutamate receptor-like proteins (GLRs) shares similarities to animal iGluRs in sequence and predicted secondary structure. However, the function of GLRs in plants is little known. In the present study, a serine site (Ser-860) of AtGLR3.7 phosphorylated by a calcium-dependent protein kinase (CDPK) was identified and confirmed by an in vitro kinase assay. Using a bimolecular fluorescence complementation and quartz crystal microbalance analyses, the physical interaction between AtGLR3.7 and the 14-3-3ω protein was confirmed. The mutation of Ser-860 to alanine abolished this interaction, indicating that Ser-860 is the 14-3-3ω binding site of AtGLR3.7. Compared with wild type, seed germination of the glr3.7-2 mutant was more sensitive to salt stress. However, the primary root growth of GLR3.7-S860A overexpression lines was less sensitive to salt stress than that of the wild-type line. In addition, the increase of cytosolic calcium ion concentration by salt stress was significantly lower in the glr3.7-2 mutant line than in the wild-type line. Moreover, association of 14-3-3 proteins to microsomal fractions was less in GLR3.7-S860A overexpression lines than in GLR3.7 overexpression line under 150 mM NaCl salt stress condition. Overall, our results indicated that GLR3.7 is involved in salt stress response in A. thaliana by affecting calcium signaling.

The ionotropic glutamate receptor (iGluR) plays an important role in neuronal signaling in animal cells. There are at least 20 glutamate receptor-like (GLR) genes in Arabidopsis thaliana . These genes are involved in seed germination, root growth, wounding response, stomata closure, etc . A recent study showed that Arabidopsis clade III glutamate receptor GLR3.7 is involved in salt stress response. We tested whether GLR3.7 is involved in abscisic acid (ABA) response. In the present study, we found that the expression of GLR3.7 was reduced by ABA treatment. Under ABA-treated condition, GLR3.7 overexpression lines exhibited significantly higher seed germination rate at 60, 72 and 84 h under ABA-treated condition. A point mutation in 14-3-3 binding site of GLR3.7 in GLR3.7-S860A overexpression lines exhibited higher seed germination inhibition under ABA-treated conditions. Our results support that GLR3.7 is involved in ABA response in Arabidopsis. In addition, Ser-860 of GLR3.7 appears to be important in ABA response.