GLR Channels Are Involved in the Mechanism of Chloroplast Avoidance Response in Lemna trisulca

(1) Background: The complete signalling pathway leading to light-induced chloroplast movement in plant cells is not yet fully understood. The process may involve GLR channels, which have previously been shown to participate in light signalling in plants. Therefore, using in vivo photometry we analysed chloroplast movements in the water plant Lemna trisulca treated with GLR channel inhibitors, MK-801 and CNQX. (2) Results: MK-801, a non-competitive antagonist that blocks NMDA channels was found to inhibit the avoidance response of chloroplasts controlled by phototropin2. This inhibition depends on pH and requires alkaline conditions. On the contrary, CNQX, a competitive receptor antagonist that blocks AMPA channels did not change the parameters of chloroplast movements in either mild alkaline or acidic conditions. (3) Conclusions: Our study reveals that GLR NMDA channels play a role in chloroplast movements and provides new insights into the phot2 signalling pathway. The results also suggest that the activity of these channels depends on pH, similar to NMDA receptors present in animal cells.