The Ca2+ signaling, Glu, and GABA responds to Cd stress in duckweed

Cadmium (Cd) affects plants and animal health seriously. Ca2+ signals in plant cells are important for adaptive responses to environmental stresses. Here we showed that 50 mu M Cd shock stimulated the Ca2+ signal via modifying the instantaneous Ca2+ flux from influx of 17 pmol.cm(-2).s(-1) to the efflux of 240 pmol.cm(-2).s(-1) at 100 mu m from rhizoid tip. And the Ca2+ signal transferred to the vein and mesophyll cell. The Ca addition decreased the accumulation of Cd. The gene expression of glutamate receptor-like (GLR) proteins, which is activated by Glu and triggers Ca2+ flux, was increased significantly by 24 h Cd stress. Glu content was increased under Cd stress and exogenous Glu triggered the Ca2+ signal in duckweed, while Ca2+ addition caused no influence to Glu content. GABA, which is synthesized from Glu and acts as an inhibitory neurotransmitter, has been decreased with 24 h Cd treatment. GABA addition increased the abscission rate and Glu addition decreased the abscission rate during Cd stress, suggesting that the Glu/GABA ratio is important for responding to Cd. This research shows the sight of the Glu, Ca2+, GABA signaling networks during Cd stress.