Figure 2.

Regulatory network of stress responses to drought, salt, and cold: specificity and cross-talk. The common osmotic component of drought, salt, and cold leads to common signaling pathways mediated by several kinases like AtSK, SnRK2, SnRK3, MAPK, and CDPK proteins. Calcium was shown to be an upstream element in some SnRK3, CDPK, and MAPK activation, whereas PA, ABA, and H₂O₂ are presumed to be involved in SnRK2 and/or MAPK regulation. In addition to these common signaling events, some pathways are specific to one stress condition like the SOS pathway regulating sodium homeostasis in response to NaCl, and the SnRK2.6-mediated stomatal closure induced by ABA in response to drought. In major cases, downstream responses regulated by protein kinases are still unknown.