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Abstract

Rapid biosynthesis of abscisic acid (ABA) in the leaf, triggered by a decrease in cell volume, is essential for a functional stomatal response to vapour pressure deficit (VPD) in angiosperms. However, it is not known whether rapid biosynthesis of ABA is triggered in other plant tissues as well. Through the application of external pressure to flower, root and leaf tissues, we test whether a reduction in cell volume can trigger rapid increases in ABA levels across plant body in two species Solanum lycopersicum and Passiflora tarminiana. Our results show that, in contrast to rapid ABA synthesis in the leaf, flower and root tissue did not show a significant, rapid increase in ABA level in response to a drop in cell volume over a short time-frame, suggesting that fast ABA biosynthesis occurs only in leaf, not in flower or root tissues. A gene encoding the key, rate-limiting carotenoid cleavage enzyme (9`-cis-epoxycarotenoid dioxygenase, NCED) in ABA biosynthetic pathway in S. lycopersicum, NCED1, was unregulated to lesser degree in flowers and roots compared to leaves in response to applied pressure. In both species, floral tissues contained substantially lower levels of NCED substrate 9`-cis-neoxanthin than leaves, and this ABA precursor could not be detected in roots. Slow and minimal ABA biosynthesis was detected after 2 h in petals, indicating that floral tissue is capable of synthesising ABA in response to sustained water deficit. Our results indicate that rapid ABA biosynthesis predominantly occurs in the leaves, and not in other tissues.

Item Type:	Article
Authors/Creators:	Zhang, F-P and Sussmilch, F and Nichols, DS and Cardoso, AA and Brodribb, TJ and McAdam, SAM
Keywords:	abscisic acid, 9`-cis-epoxycarotenoid dioxygenase, stomata, cell volume, flowers, roots
Journal or Publication Title:	Journal of Experimental Botany
Publisher:	Oxford Univ Press
ISSN:	0022-0957
DOI / ID Number:	10.1093/jxb/erx480
Copyright Information:	Copyright 2018 The Authors. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/
Related URLs:	Google Scholar: Sussmilch, F UTAS Profile: Sussmilch, F Google Scholar: Nichols, DS UTAS Profile: Nichols, DS Google Scholar: Brodribb, TJ UTAS Profile: Brodribb, TJ
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