Glutamate Receptor Homolog3.4 is Involved in Regulation of Seed Germination Under Salt Stress in Arabidopsis

Abstract

Seed germination is sensitive to salt stress. ABA and Ca2+ are involved in the regulation of seed germination under salt stress. Ca2+ influx mediated by glutamate receptors (GLRs) plays important roles in many physiological processes in plants. Here, we investigated the correlation of GLRs, Ca2+ and ABA during seed germination in response to salt stress by using Arabidopsis thaliana wild-type and T-DNA insertion knockout mutants of glutamate receptor homolog3.4. We demonstrated that atglr3.4-1 and atglr3.4-2 mutants were more sensitive to NaCl during seed germination and post-germination growth than wild-type plants. Treatments of wild-type seedlings with NaCl evoked a marked elevation in cytosolic Ca2+ activity ([Ca2+]cyt), and the elevation was inhibited by antagonists of GLRs, while the NaCl-induced elevation in [Ca2+]cyt was impaired in atglr3.4-1 and atglr3.4-2 mutants. Moreover, the mutants exhibited a lower expression of SOS3, SOS2 and SOS1, and greater accumulation of Na+ than wild-type seeds in the presence of NaCl. Mutation of AtGLR3.4 rendered the mutants more sensitive to ABA, while overexpression of AtGLR3.4 made the transgenic lines more tolerant to ABA in terms of seed germination. However, there was no difference in ABA content between atglr3.4 mutants and wild-type seeds, accompanied by lower expression of ABI3 and ABI4 in atglr3.4 mutants when challenged with NaCl. These results demonstrate that AtGLR3.4-mediated Ca2+ influx may be involved in the regulation of seed germination under salt stress by modulating Na+ accumulation through the SOS pathway.

Signaling Role of Glutamate in Plants

“…As discussed above, seed germination is sensitive and fragile to environmental stress including NaCl stress, and Ca 2+ and ABA regulate seed germination under NaCl stress. In A. thaliana, the results of Cheng et al (2018) showed that, compared with the wild-type plants, the AtGLR3.4-1 and AtGLR3.4-2 mutant plants were more sensitive to NaCl in both seed germination and postgermination seedling growth. In addition, in wild-type seedlings, NaCl triggered a striking increase in [Ca 2+ ] cyt , but this increase was blocked by DNQX (GLR antagonist); whereas in both AtGLR3.4-1 and AtGLR3.4-2 mutants NaCl-triggered increase in [Ca 2+ ] cyt was impaired (Cheng et al, 2018).…”

“…In A. thaliana, the results of Cheng et al (2018) showed that, compared with the wild-type plants, the AtGLR3.4-1 and AtGLR3.4-2 mutant plants were more sensitive to NaCl in both seed germination and postgermination seedling growth. In addition, in wild-type seedlings, NaCl triggered a striking increase in [Ca 2+ ] cyt , but this increase was blocked by DNQX (GLR antagonist); whereas in both AtGLR3.4-1 and AtGLR3.4-2 mutants NaCl-triggered increase in [Ca 2+ ] cyt was impaired (Cheng et al, 2018). Also, under NaCl stress, both mutants showed a lower expression of salt overly sensitive (SOS3), SOS2, and SOS1, as well as more accumulation of Na + than wild-type seeds (Cheng et al, 2018).…”

“…Recently, in plants, in addition to above-mentioned functions, Glu is found to emerge as a novel signaling role in many physiological processes. These processes include seed germination (Kong et al, 2015), root architecture (Forde, 2014;López-Bucio et al, 2019), pollen germination and pollen tube growth (Michard et al, 2011;Wudick et al, 2018), wound response and pathogen resistance (Manzoor et al, 2013;Mousavi et al, 2013;Nguyen et al, 2018;Toyota et al, 2018;Jin et al, 2019), and response and adaptation to abiotic stress (Cheng et al, 2018;Zheng et al, 2018;Li H. et al, 2019;Philippe et al, 2019). In addition, Glu can act as a long-distance signaling transducer among cells, tissues, organs, and even the whole plants by the crosstalk with Ca 2+ , ROS, and electrical signaling (Mousavi et al, 2013;Nguyen et al, 2018;Toyota et al, 2018).…”

Chloroplast Calcium Signaling in the Spotlight

“…AtGLR3.4 and AtGLR3.5, two Ca 2+ -permeable channels belonging to the GLR family, have a dual localization, at the plasma membrane and chloroplasts the former (Teardo et al, 2010;Teardo et al, 2011), in mitochondria and chloroplasts the latter (Teardo et al, 2015). Both seem to play a role in ABA signaling under abiotic stress (Cheng et al, 2018;Ju et al, 2020), although their direct involvement in organellar Ca 2+ signaling under abiotic stress has to be investigated more in depth.…”

Effects of Exogenous Trehalose on the Metabolism of Sugar and Abscisic Acid in Tomato Seedlings Under Salt Stress

“…In recent years, increasing research attention has been paid to salt stress that can affect the growth and development of plants, especially in the stage of seed germination [1,2]. The response of plants to salt stress is complex, which is achieved through a variety of physiological and biochemical reactions and molecular mechanisms, and also involves the differential expression of stress-related genes in the corresponding pathways [3][4][5].…”