Catalyzes the attachment of glycine to tRNA(Gly). Is also able produce diadenosine tetraphosphate (Ap4A), a universal pleiotropic signaling molecule needed for cell regulation pathways, by direct condensation of 2 ATPs. ATP + glycine + tRNA(Gly) = AMP + diphosphate + glycyl-tRNA(Gly) Homodimer. Embryo defective. Developmental arrest of the embryo between the globular and heart stages (PubMed:9707529). Plants with partial loss of EDD1 display changes in patterning of margin and distal regions of leaves (PubMed:22791832). May be due to a competing donor splice site. Belongs to the class-II aminoacyl-tRNA synthetase family.