Figure 1.

Relation tree of the SnRK2 family from Arabidopsis and rice. Arabidopsis SnRK2s are drawn with black lines and rice SAPKs are drawn with gray lines. Based on transient expression assays, SnRK2 proteins activated by hyperosmotic conditions can be divided into three groups, depending on additional activation by ABA. Group 1 corresponds to kinases strongly activated by ABA, whereas in group 2, SnRK2s are not responsive to ABA. Group 3 includes kinases poorly or not activated by ABA. The Arabidopsis SnRK2.9 does not fit into any of the groups due to the lack of activation by hyperosmolarity.