Glutamate signaling enhances the heat tolerance of maize seedlings by plant glutamate receptor-like channels-mediated calcium signaling

Glutamate (Glu), a neurotransmitter in animal, is a novel signaling molecule in plants, which takes part in cellular metabolism, seed germination, plant growth, development, and long-distance information transfer. However, whether Glu can enhance the heat tolerance in maize seedlings and its relation to calcium signaling is still elusive. In this study, maize seedlings were pretreated with Glu and then exposed to heat stress. The results showed that Glu pretreatment enhanced the survival percentage of maize seedlings under heat tolerance, indicating that Glu could increase the heat tolerance of maize seedlings. The Glu-induced heat tolerance was weakened by exogenous calcium chloride, plasma membrane Ca2+ channel blocker (LaCl3), Ca2+ chelator (ethylene glycol-bis(b-aminoethylether)-N,N, N΄,N΄-tetraacetic acid), calmodulin antagonists (trifluoperazine and chlopromazine), and plant glutamate receptor-like antagonists (MgCl2 and 6,7-dinitroquinoxaline- 2,3-(1H,4H)- dione). These findings for the first time reported that Glu could increase the heat tolerance of maize seedlings by plant glutamate receptor-like channels-mediated calcium signaling.