Regulative role of calcium signaling on methylglyoxal-improved heat tolerance in maize ( Zea mays L) seedlings

Nowadays, calcium (Ca²⁺) and methylglyoxal (MG) are all deemed to be second messengers in plants, which participate in various physiological processes, such as seed germination, seedling establishment, plant growth and development, as well as response to environmental stress. However, the Ca²⁺-MG interaction in the development of thermotolerance in maize seedlings remains unclear. Here, using maize seedlings as materials, the crosstalk between Ca²⁺ and MG signaling in the acquisition of thermotolerance was explored. The results showed that root-irrigation with Ca²⁺ and MG alone or in combination increased the survival rate of maize seedlings under heat stress, mitigated the decrease in the tissue vitality, and reduced the membrane lipid peroxidation (in term of the content of malondialdehyde), indicating that Ca²⁺ and MG could improve the thermotolerance in maize seedlings. In addition, MG-improved thermotolerance was impaired by ethylene glycol-bis(b-aminoethylether)-N,N,N΄,N΄-tetraacetic acid (a Ca²⁺ chelator), La³⁺ (plasma membrane Ca²⁺ channel blocker), ruthenium red (a mitochondrial Ca²⁺ channel blocker), neomycin (vacuole Ca²⁺ channel blocker), caffeine (an endoplasmic reticulum Ca²⁺ channel blocker), and calmodulin antagonists (chlorpromazine and trifluoperazine), respectively. Also, MG scavengers (N-acetyl-cysteine, aminoguanidine, and vitamin B6) had no significant effect on Ca²⁺-triggered thermotolerance (in terms of survival rate, malondialdehyde, and tissue vitality) of maize seedlings. The data illustrated that calcium signaling regulated MG-improved thermotolerance in maize seedlings by mobilizing intracellular and extracellular Ca²⁺ pools.

Keywords: Calcium signaling; heat stress; maize seedlings; methylglyoxal signaling; thermotolerance.