title: Expression of ABA synthesis and metabolism genes under different irrigation strategies and atmospheric VPDs is associated with stomatal conductance in grapevine (Vitis vinifera L. cv Cabernet Sauvignon).
abstract: The influence of different levels of irrigation and of variation in atmospheric vapour pressure deficit (VPD) on the synthesis, metabolism, and transport of abscisic acid (ABA) and the effects on stomatal conductance were examined in field-grown Cabernet Sauvignon grapevines. Xylem sap, leaf tissue, and root tissue were collected at regular intervals during two seasons in conjunction with measurements of leaf water potential (Ψleaf) and stomatal conductance (gs). The different irrigation levels significantly altered the Ψleaf and gs of the vines across both seasons. ABA abundance in the xylem sap was correlated with gs. The expression of genes associated with ABA synthesis, NCED1 and NCED2, was higher in the roots than in the leaves throughout and highest in the roots in mid January, a time when soil moisture declined and VPD was at its highest. Their expression in roots was also inversely related to the levels of irrigation and correlated with ABA abundance in the roots, xylem sap, and leaves. Three genes encoding ABA 8'-hydroxylases were isolated and their identities confirmed by expression in yeast cells. The expression of one of these, Hyd1, was elevated in leaves when VPD was below 2.0-2.5 kPa and minimal at higher VPD levels. The results provide evidence that ABA plays an important role in linking stomatal response to soil moisture status and that changes in ABA catabolism at or near its site of action allows optimization of gas exchange to current environmental conditions.
authors: Commonwealth Scientific and Industrial Research Organisation, PO Box 350, Glen Osmond, South Australia 5062, Australia. Jim.Speirs@csiro.au
authors: Jim
authors: J
authors: Speirs
authors: Allan
authors: A
authors: Binney
authors: Marisa
authors: M
authors: Collins
authors: Everard
authors: E
authors: Edwards
authors: Brian
authors: B
authors: Loveys
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D057914:Agricultural Irrigation; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D018526:Plant Transpiration / Q000502:physiology; D027843:Vitis / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D000040:Abscisic Acid; D003577:Cytochrome P-450 Enzyme System; C107203:abscisic acid 8'-hydroxylase
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