Plants dynamically regulate water use by the movement of stomata on the surface of leaves. Stomatal responses to changes in vapour pressure deficit (VPD) are the principal regulator of daytime transpiration and water use efficiency in land plants. In angiosperms, stomatal responses to VPD appear to be regulated by the phytohormone abscisic acid (ABA), yet the origin of this ABA is controversial. After a 20 minute exposure of plants, from three diverse angiosperm species, to a doubling in VPD, stomata closed, foliar ABA levels increased and the expression of the gene encoding the key, rate-limiting carotenoid cleavage enzyme (9-cis-epoxycarotenoid dioxygenase, NCED) in the ABA biosynthetic pathway was significantly upregulated. The NCED gene was the only gene in the ABA biosynthetic pathway to be upregulated over the short time scale corresponding to the response of stomata. The closure of stomata and rapid increase in foliar ABA levels could not be explained by the release of ABA from internal stores in the leaf or the hydrolysis of the conjugate ABA-glucose ester. These results implicate an extremely rapid de novo biosynthesis of ABA, mediated by a single gene, as the means by which angiosperm stomata respond to natural changes in VPD.

Item Type:	Refereed Article
Keywords:	abscisic acid (ABA), 9-cis-epoxycarotenoid dioxygenase, stomata, vapour pressure deficit, ABA-GE
Research Division:	Biological Sciences
Research Group:	Plant biology
Research Field:	Plant physiology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the biological sciences
UTAS Author:	McAdam, SAM (Dr Scott McAdam)
UTAS Author:	Sussmilch, FC (Dr Frances Sussmilch)
UTAS Author:	Brodribb, TJ (Professor Tim Brodribb)
ID Code:	102994
Year Published:	2016
Funding Support:	Australian Research Council (DE140100946)
Web of Science® Times Cited:	103
Deposited By:	Plant Science
Deposited On:	2015-09-15
Last Modified:	2022-08-18
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