Cyclic nucleotide-gated ion channel 6 mediates thermotolerance in Arabidopsis seedlings by regulating nitric oxide production via cytosolic calcium ions

BACKGROUND: We previously reported the involvement of nitric oxide (NO) and cyclic nucleotide-gated ion channel 6 (CNGC6) in the responses of plants to heat shock (HS) exposure. To elucidate their relationship with heat tolerance in Arabidopsis thaliana, we examined the effects of HS on several groups of seedlings: wild type, cngc6, and cngc6 complementation and overexpression lines. RESULTS: After HS exposure, the level of NO was lower in cngc6 seedlings than in wild-type seedlings but significantly elevated in the transgenic lines depending on CNGC6 expression level. The treatment of seeds with calcium ions (Ca(2+)) enhanced the NO level in Arabidopsis seedlings under HS conditions, whereas treatment with EGTA (a Ca(2+) chelator) reduced it, implicating that CNGC6 stimulates the accumulation of NO depending on an increase in cytosolic Ca(2+) ([Ca(2+)](cyt)). This idea was proved by phenotypic observations and thermotolerance testing of transgenic plants overexpressing NIA2 and NOA1, respectively, in a cngc6 background. Western blotting indicated that CNGC6 stimulated the accumulation of HS proteins via NO. CONCLUSION: These data indicate that CNGC6 acts upstream of NO in the HS pathway, which improves our insufficient knowledge of the initiation of plant responses to high temerature. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12870-019-1974-9) contains supplementary material, which is available to authorized users.