ZmCK3, a maize calcium-dependent protein kinase gene, endows tolerance to drought and heat stresses in transgenic Arabidopsis

Calcium-dependent protein kinases (CDPKs) play an essential role in calcium-mediated signal transductions in plant cells. We isolated a candidate gene encoding a calcium-dependent protein kinase, named ZmCK3, from maize seedlings. The predicted ZmCK3 protein contains a typical conserved CDPK structure, a Ser/Thr kinase domain and four EF-hand domains. A ZmCK3::hGFP fusion protein was localized on the plasma membrane and in the nucleus when introduced into Arabidopsis mesophyll protoplasts. ZmCK3 transcripts were highly induced by drought, salt, and heat in maize seedlings. Isolation of the ZmCK3 promoter revealed some cis-acting elements that respond to stress. Overexpression of ZmCK3 improved plant survival rates under drought and heat conditions in transgenic Arabidopsis plants. Based on this evidence, ZmCK3 is involved in responses to environmental stresses, and that ZmCK3 may be important components in the signal transduction pathways for stress responses.