The role of calcium in ABA-induced gene expression and stomatal movements
2001
Webb, A.A.R. | Larman, M.G. | Montgomery, L.T. | Taylor, J.E. | Hetherington, A.M.
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 Ca(2+)-dependent and -independent ABA-signalling pathways are present in guard cells. Our data suggest that increases in [Ca(2+)]i are a common component of the guard cell ABA-turgor and ABA-nuclear signalling pathways. The effects of Ca(2+) antagonists on ABA-induced stomatal closure and the ABA-responsive CDeT6-19 gene promoter suggest that Ca(2+) 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 Ca(2+)-independent signalling elements are present in the guard cell, they do not form a completely separate Ca(2+)-independent ABA-signalling pathway.
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