Glutamate receptors are involved in mitigating effects of amino acids on seed germination of Arabidopsis thaliana under salt stress

• Seed germination in wild-type Arabidopsis thaliana was suppressed by exposure to NaCl.
• The inhibitory effects of NaCl on seed germination were markedly mitigated by exogenous application of those amino acids Gly, Cys, Ser and Met.
• Glutamate receptor antagonist and Ca channel blocker potentiated the inhibory effect of NaCl on seed germination.
• Seed germination of glutamate receptor mutants, atglr3.4 and atglr3.7, were more sensitive to NaCl and the amino acids had less mitigating effects.

Seed germination is an elaborate process during life cycle and regulated by numerous intrinsic and environmental cues. The role of amino acids in seed germination under salt stress has been reported, however the underlying mechanisms by which amino acids mitigate salt stress-induced seed germination remain largely elusive. Here, we reported that seed germination of Arabidopsis thaliana wild-type was suppressed by exposure to salt stress, and that the inhibition was markedly alleviated by exogenous application of those amino acids including Gly, Cys, Ser and Met. Calcium channel blocker La3+ suppressed the mitigating effect of those amino acids on seed germination under salt stress. We further demonstrated that germination of wild-type seeds was suppressed by the glutamate receptor (GLR) antagonist 6,7-dinitriquinoxaline-2,3-dinoe (DNQX) under salt stress and the alleviative effects of amino acid on seed germination under salt stress were suppressed by DNQX. In addition, mutation of clade 3 GLRs led to lower seed germination rates of atglr3.4 and atglr3.7 mutants than those of wild-type seeds when exposed to NaCl and the mitigating effects of amino acids on seed germination rates of atglr3.4 and atglr3.7 were less effective than those of wild-type seeds. Moreover, seed germination of atglr3.4-1, atglr3.4-2 and atglr3.7 mutants were less sensitive to CaCl2 and DNQX than wild-type under salt stress. Taken together, these findings highlight the involvement of GLR-dependent Ca2+ influx in alleviation of salt stress-induced inhibition of seed germination by exogenous amino acids.