(+)-Abscisic Acid Metabolism, 3-Ketoacyl-Coenzyme A Synthase Gene Expression, and Very-Long-Chain Monounsaturated Fatty Acid Biosynthesis inBrassica napus Embryos1

Abstract

Microspore-derived embryos of Brassica napus cv

Reserve Mobilization in the Arabidopsis Endosperm Fuels Hypocotyl Elongation in the Dark, Is Independent of Abscisic Acid, and Requires PHOSPHOENOLPYRUVATE CARBOXYKINASE1

“…Hence, it is possible that decreased sensitivity of the endosperm to ABA during seed development could underlie differences in the fatty acid composition of the embryo and endosperm in mature seeds. ABA is also known to enhance LCFA biosynthesis in rape embryos and to induce the expression of a fatty acid elongase (Finkelstein and Somerville, 1989;Qi et al, 1998). Although this is not completely consistent with the results presented here, it does underline the potential importance of ABA in the regulation of storage lipid accumulation.…”

(+)-Abscisic Acid 8′-Hydroxylase Is a Cytochrome P450 Monooxygenase

“…Cutler, unpublished data). Circumstantial evidence suggests that this enzyme is particularly active in developing seeds and germinating seedlings, in young and expanding leaves, in roots and tubers, and in tissues recovering from abiotic stresses (Creelman and Zeevaart, 1984;Zhang and Davies, 1987;Vreugdenhil et al, 1994;Garello and LePageDegivry, 1995;Walton and Li, 1995;Jia et al, 1996;Zhang et al, 1997;Qi et al, 1998). This supposition was examined in germinating cress seed using a deuterated analog of (ϩ)-ABA, (ϩ)-d 9 -ABA (Lamb et al, 1996).…”

“…Some of the metabolic markers used to identify potential tissues expressing this enzyme have included the disappearance of internal or applied ABA, the accumulation of PA and DPA or their Glc conjugates, and reduced sensitivity to applied ABA (Uknes and Ho, 1984;Garello and LePage-Degivry, 1995;Jia et al, 1996;Cutler et al, 1997;Qi et al, 1998). Such data imply that ABA 8Ј-hydroxylase is expressed at high levels in plant tissues recovering from abiotic stresses such as water stress (Creelman and Zeevaart, 1984;Walton and Li, 1995), in roots and tubers (Zhang and Davies, 1987;Vreugdenhil et al, 1994), and in leaves, developing seeds, and seedlings (Gillard and Walton, 1976;Babiano, 1995;Garello and LePage-Degivry, 1995;Jia et al, 1996;Zhang et al, 1997;Qi et al, 1998). ABA degradation can be very rapid; the half-life of radioactive ABA applied through the xylem of detached leaves of maize (Zea mays) and Commelina communis was 42 and 64 min, respectively (Jia et al, 1996), and the turnover of ABA taken up from the medium in maize root tips was greater than 60% in a 1-h period (Ribaut et al, 1996).…”

Abscisic acid metabolism and lipid accumulation of a cell suspension culture of Lesquerella fendleri

“…For example, zygotic embryos of Brassica napus L. cv. Nugget and L. cv Reston accumulate verylong-chain fatty acids in response to high osmoticum, achieved by the addition of high concentrations of sorbitol or additions of ABA (Finkelstein and Somerville 1989;Zou et al, 1995;Qi et al, 1998). Specifically, ABA treatments increased levels of eicosenoic (20:1 Δ11)…”