The role of calcium in ABA-induced gene expression and stomatal movements.
There is much interest in the transduction pathways by which abscisic acid (ABA) regulates stomatal movements (ABA-turgor signalling) and by which this phytohormone regulates the pattern of gene expression in plant cells (ABA-nuclear signalling). A number of second messengers have been identified in both the ABA-turgor and ABA-nuclear signalling pathways. A major challenge is to understand the architecture of ABA-signalling pathways and to determine how the ABA signal is coupled to the appropriate response. We have investigated whether separate Ca2+-dependent and -independent ABA-signalling pathways are present in guard cells. Our data suggest that increases in [Ca2+]i are a common component of the guard cell ABA-turgor and ABA-nuclear signalling pathways. The effects of Ca2+ antagonists on ABA-induced stomatal closure and the ABA-responsive CDeT6-19 gene promoter suggest that Ca2+ is involved in both ABA-turgor signalling and ABA-nuclear signalling in guard cells. However, the sensitivity of these pathways to alterations in the external calcium concentration differ, suggesting that the ABA-nuclear and ABA-turgor signalling pathways are not completely convergent. Our data suggest that whilst Ca2+-independent signalling elements are present in the guard cell, they do not form a completely separate Ca2+-independent ABA-signalling pathway.
Webb
A A
AA
Department of Biological Sciences, Institute of Environmental and Natural Sciences, Lancaster University, Bailrigg, Lancaster LA1 4YQ, UK. aarw2@cam.ac.uk
Larman
M G
MG
Montgomery
L T
LT
Taylor
J E
JE
Hetherington
A M
AM
D000040:Abscisic Acid / Q000502:physiology*; D017360:Arabidopsis / Q000166:cytology / Q000502:physiology; D002118:Calcium / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D019684:Magnoliopsida / Q000166:cytology / Q000502:physiology; D018515:Plant Leaves / Q000166:cytology / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics; D015398:Signal Transduction
C086761:CDeT6-19 protein, Craterostigma plantagineum; D010940:Plant Proteins; D000040:Abscisic Acid; D002118:Calcium