Signaling molecule glutamic acid initiates the expression of genes related to methylglyoxal scavenging and osmoregulation systems in maize seedlings

Glutamic acid (Glu) is not only a protein amino acid, but also a signaling molecule, which takes part in various physiological processes in plants. Our previous study found that root-irrigation with Glu could improve the heat tolerance of maize seedlings by plant Glu receptor-like channels-mediated calcium signaling (Protoplasma, 2019; 256:1165–1169), but its molecular mechanism remains unclear. In this study, based on the our previous work, the maize seedlings were treated with 1 mM Glu prior to be exposed to heat stress (HS), and then the expression of genes related to related to methylglyoxal (MG)-scavenging and osmoregulation systems was quantified. The results showed that Glu treatment up-regulated the gene expression of Zea mays aldo-keto reductase (ZmAKR) under both non-HS and HS conditions. Also, the gene expression of Zea mays alkenal/alkenone reductase (ZmAAR), glyoxalase II (ZmGly II), pyrroline-5-carboxylate synthase (ZmP5CS), betaine dehydrogenase (ZmBADH), and trehalase (ZmTRE) was up-regualted by exogenous Glu treatment under HS conditions. These data imply that signaling molecule Glu initiated the expression of genes related to MG-scavenging and osmoregulation systems in maize seedlings, further supporting the fact that Glu-enhanced heat tolerance in plants.