Salt and drought stress signal transduction in plants.
Zhu JK.
Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.
jkzhu@ag.arizona.edu
Salt and drought stress signal transduction consists of ionic and osmotic
homeostasis signaling pathways, detoxification (i.e., damage control and repair)
response pathways, and pathways for growth regulation. The ionic aspect of salt
stress is signaled via the SOS pathway where a calcium-responsive SOS3-SOS2
protein kinase complex controls the expression and activity of ion transporters
such as SOS1. Osmotic stress activates several protein kinases including mitogen-activated
kinases, which may mediate osmotic homeostasis and/or detoxification responses.
A number of phospholipid systems are activated by osmotic stress, generating a
diverse array of messenger molecules, some of which may function upstream of the
osmotic stress-activated protein kinases. Abscisic acid biosynthesis is
regulated by osmotic stress at multiple steps. Both ABA-dependent and
-independent osmotic stress signaling first modify constitutively expressed
transcription factors, leading to the expression of early response
transcriptional activators, which then activate downstream stress tolerance
effector genes.