Contrasting interactions between ethylene and abscisic acid in Rumex species differing in submergence tolerance

Abstract

SummaryComplete submergence of flooding-tolerant Rumex palustris plants strongly stimulates petiole elongation. This escape response is initiated by the accumulation of ethylene inside the submerged tissue. In contrast, petioles of flooding-intolerant Rumex acetosa do not increase their elongation rate under water even though ethylene also accumulates when they are submerged. Abscisic acid (ABA) was found to be a negative regulator of enhanced petiole growth in both species. In R. palustris, accumulated ethylene stimulated elongation by inhibiting biosynthesis of ABA via a reduction of RpNCED expression and enhancing degradation of ABA to phaseic acid. Externally applied ABA inhibited petiole elongation and prevented the upregulation of gibberellin A 1 normally found in submerged R. palustris. In R. acetosa submergence did not stimulate petiole elongation nor did it depress levels of ABA. However, if ABA concentrations in R. acetosa were first artificially reduced, submergence (but not ethylene) was then able to enhance petiole elongation strongly. This result suggests that in Rumex a decrease in ABA is a prerequisite for ethylene and other stimuli to promote elongation.

Ethylene is an endogenous stimulator of cell division in the cambial meristem of Populus

“…It is plausible that ethylene is a primary response to leaning, potentiating growth responses that are regulated through downstream interactions with other phytohormones. In deepwater rice and Rumex palustris, for example, the induction of ethylene upon submergence stimulated elongation growth by acting through inhibition of abscisic acid biosynthesis, which in turn led to a stimulation of GA biosynthesis (25,(29)(30)(31). Considering the recent demonstration of ethylene-induced auxin biosynthesis in Arabidopsis roots (32)(33)(34), together with the long-standing idea that ethylene interacts with auxin polar transport both in herbaceous plants and trees (35,36), auxin could be a joint mediator that stimulates cambial growth upon leaning.…”

Waterproofing Crops: Effective Flooding Survival Strategies

“…Underwater escape by Rumex palustris and quiescence of Rumex acetosa are conferred by distinctions in the elongation of leaf petioles involving the same ethylene, ABA, and GA hierarchy established for rice (Benschop et al, 2005;Bailey-Serres and Voesenek, 2008). For example, ABA insensitivity corresponded to greater underwater petiole elongation in R. palustris ecotypes (Chen et al, 2010).…”

Ethylene Insensitivity Results in Down-Regulation of Rubisco Expression and Photosynthetic Capacity in Tobacco

“…Arabidopsis ein2 mutants show an increase in the transcript levels of the ABA biosynthesis gene ZEP1, suggesting that ethylene signaling partially represses the biosynthesis of ABA (Ghassemian et al, 2000;Cheng et al, 2002). In addition, elevated ethylene concentrations strongly inhibit ABA production in submerged rice (Oryza sativa) and Rumex palustris plants (Hoffmann-Benning and Kende, 1992; Benschop et al, 2005). Therefore, it is likely that in ethylene-insensitive tobacco plants, Glc hypersensitivity with respect to Rubisco RNA and protein levels is a result of a constitutively elevated ABA concentration.…”

“…ABA extractions were done as described in Benschop et al (2005), using deuterated ABA as a reference. The samples were measured using gas chromatography-mass spectrometry analysis (5890 MSD; Agilent).…”