Table 2. Expression profiles of MKK genes under different stress treatments in cotton.

Gene	Group	Signaling molecules			Environmental stress factors
		JA (100 μM)	ABA (100 μM)	SA (10 mM)	H2O2 (10 mM)	Salt (200 mM)	PEG6000 (20%)	4 °C	37 °C	Wounding
MKK1	A	**	*	**	*	**	**	–	–	*
MKK2_1	A	*	*	**	*	**	*	–	–	*
MKK2_2	A	**	**	**	**	–	*	D	D	**
MKK6	A	**	**	**	**	*	**	**	**	**
MKK3	B	*	D	**	*	D	–	D	D	D
MKK4	C	–	*	**	D	*	–	–	–	**
MKK5	C	–	**	**	**	**	*	*	*	**
MKK7	D	**	**	**	**	**	**	**	**	**
MKK10_1	D	**	**	**	**	**	*	**	D	**
MKK10_2	D	*	–	**	**	**	D	**	D	**

Note: For hormone treatments, the leaves of seedlings were harvested at 0, 0.5, 1, 2, 4, 6, 8, 10, 12 and 24 h after treatment; For the environmental stress factor treatments, the leaves of seedlings were harvested at 0, 0.5, 1, 2, 4, 6, 8, 10, 12 and 24 h after treatment; “**” and “*” indicate significant difference at P < 0.01 and P < 0.05, respectively; “–” represents no change and weak upregulation; “D” represents significant reduction in MKK gene expression after treatment; The Student’s t-test was performed between treated samples and untreated samples.