Abscisic acid regulation of heterophylly in Marsilea quadrifolia L.: effects of R-(−) and S-(+) isomers

Abstract

The plant hormone abscisic acid (ABA) induces a developmental switch in the aquatic fern Marsilea quadrifolia, causing the formation of aerial type characteristics, including the elongation of petioles and roots, a change in leaf morphology, the expansion of leaf surface area, and the shortening of the internodes. A number of ABA-responsive heterophylly (ABRH) genes are induced early during the transition. Using optically pure isomers of ABA, it was found that both the natural S-(+)-ABA and the unnatural R-(-)-ABA are capable of inducing a heterophyllous switch and regulating ABRH gene expression. When dose responses are compared, the unnatural ABA gives stronger morphogenic effects than the natural ABA at the same concentration, it is effective at lower concentrations, and its optimal concentration is also lower compared with the natural ABA. Deuterium-labelled ABA enantiomers were used to trace the fate of applied ABA and to distinguish the applied compound and its metabolites from the endogenous counterparts. In tissues, the supplied (+)-ABA was metabolized principally to dihydrophaseic acid, while the supplied (-)-ABA was converted at a slower rate to 7'-hydroxy abscisic acid. Treatment with either enantiomer resulted in increased biosynthesis of ABA, as reflected in the accumulation of endogenous dihydrophaseic acid. Taken together, these results suggest two distinct mechanisms of action for (-)-ABA: either (-)-ABA is intrinsically active, or its activity is due to the stimulation of ABA biosynthesis.

Overexpression of AtMYB44 Enhances Stomatal Closure to Confer Abiotic Stress Tolerance in Transgenic Arabidopsis

“…In general, (2)-ABA has been found to be as effective as (1)-ABA. Experiments with the aquatic fern Marsilea quadrifolia suggest that (2)-ABA is either intrinsically active or its activity is caused by the stimulation of (1)-ABA biosynthesis (Lin et al, 2005). reported that the expression of AtMYB44 was not induced by (1)-ABA, but we observed that it was rapidly induced by (6)-ABA.…”

The evolution of abscisic acid (ABA) and ABA function in lower plants, fungi and lichen

“…In submerged liverworts, ABA enables the organism to occupy the terrestrial environment. This resembles the induction of terrestrial leaves in the heterophyllous water fern (Marsilea quadrifolia, Lin et al 2005) and angiosperms (Proserpinaca intermedia, Kane and Albert 1982; Ranunculus flabellaris, Young et al 1987;Potamogeton nodosus, Gee and Anderson 1998;Hippuris vulgaris, Goliber 1989; Ludwigia arcuta, Kuwabara et al 2003) that occurs under the control of ABA.…”

Abscisic acid perception and signaling: structural mechanisms and applications

“…Studies using ABA analogs lacking the 7'-, 8'-, or 9'-methyl groups showed that the 7'-methyl group is critical for bioactivity [33] . Flipping the cyclohexene ring around the chiral carbon produces the unnatural (-)-enantiomer, which has weak biological activity ( Figure 3B) [34] . Structural and functional analogs of ABA have been used to identify ABA-responsive genes, and some of these analogs are potential plant growth regulators [35,36] .…”