Seems to play an important role in controlling the expression of resistance responses like the regulation of salicylic acid (SA) and phytoalexin (camalexin) production. Involved in resistance to fungal and bacterial pathogens. Required for the regulation of cell proliferation in root apical meristems through the GSH-dependent developmental pathway. Also participates in the detoxification process, the antioxidant response and is essential for embryo development and proper seed maturation. ATP + L-cysteine + L-glutamate = ADP + gamma-L-glutamyl-L-cysteine + H(+) + phosphate Feedback inhibition by glutathione. Inhibited by buthionine sulfoximine and cystamine. Sulfur metabolism; glutathione biosynthesis; glutathione from L-cysteine and L-glutamate: step 1/2. Homodimer or monomer when oxidized or reduced, respectively. A number of isoforms are produced. According to EST sequences. Abundant in leaves and roots. Expressed to a high level in leaf trichomes of mature plant. Down-regulated in leaf trichomes under salt treatment. Up-regulated by the fungal pathogen Phytophthora porri. Induced by cadmium (PubMed:16502469). The Cys-186-Cys-406 disulfide bridge is known to modulate the enzyme activity according to the redox status. The oxidized form constitutes the active enzyme. Plants are characterized by a recessive embryo-lethal phenotype. Belongs to the carboxylate-amine ligase family. Glutamate--cysteine ligase type 2 subfamily.