Table 1.

Different signal molecules activate MAPK pathway under heavy metal stresses.

Signals	Heavy Metal	Plant	MAPK	Reference
ROS	-	Arabidopsis thaliana	MEKK1-MKK4/5-MPK3/6	[25]
	-	Arabidopsis thaliana	MEKK1-MKK2-MPK4/6	[26]
	Cu, Cd	Medicago sativa	SIMK, MMK2, MMK3 and SAMK	[27]
	Cu	Arabidopsis thaliana	MAPK	[28]
	Cd	Zea mays	ZmMPK3-1/ZmMPK6-1	[29]
	Cd	Arabidopsis thaliana	MPK3 and MPK6	[30]
NO	-	Arabidopsis thaliana	AtWAKL10	[31]
	-		MAPK	[32]
	Cd	Arabidopsis thaliana	MAPK	[33]
	Cd	Arabidopsis thaliana	MPK6	[34]
	Ar	Oryza sativa	MAPK/MPK	[35]
Hormone
		Arabidopsis thaliana	AtMPK3/AtMPK6	[36]
SA	-	Nicotiana tabacum	SIPK	[37]
ABA/IAA	Cd	Oryza sativa	MAPK	[38]
ET	Cd	Glycine max	MAPK/MAPKK2	[32]