Regulation of Abscisic Acid Signaling by the Ethylene Response Pathway in Arabidopsis

Abstract

Although abscisic acid (ABA) is involved in a variety of plant growth and developmental processes, few genes that actually regulate the transduction of the ABA signal into a cellular response have been identified. In an attempt to determine negative regulators of ABA signaling, we identified mutants, designated enhanced response to ABA3 (era3), that increased the sensitivity of the seed to ABA. Biochemical and molecular analyses demonstrated that era3 mutants overaccumulate ABA, suggesting that era3 is a negative regulator of ABA synthesis. Subsequent genetic analysis of era3 alleles, however, showed that these are new alleles at the ETHYLENE INSENSITIVE2 locus. Other mutants defective in their response to ethylene also showed altered ABA sensitivity; from these results, we conclude that ethylene appears to be a negative regulator of ABA action during germination. In contrast, the ethylene response pathway positively regulates some aspects of ABA action that involve root growth in the absence of ethylene. We discuss the response of plants to ethylene and ABA in the context of how these two hormones could influence the same growth responses.

Impaired sucrose‐induction mutants reveal the modulation of sugar‐induced starch biosynthetic gene expression by abscisic acid signalling

“…A plausible explanation for these ethylene effects and our ABA de®ciency data can be found in recent reports that ethylene appears to be a negative regulator of ABA action during germination (Beaudoin et al, 2000;Ghassemian et al, 2000).…”

Seed dormancy and germination

“…Ethylene insensitive mutants such as etr and ein2 germinate less well or after a longer period of after-ripening than wild type (Bleecker et al, 1988;Beaudoin et al, 2000). The ein2 and etr mutants are hypersensitive to ABA (Beaudoin et al, 2000;Ghassemian et al, 2000), which agrees with the observation that ein2 mutants were isolated as abi1-1 suppressors. The ctr1 mutant, which is characterised by a constitutive ethylene response, appeared among mutants selected as enhancers of the ABA insensitive mutant abi1-1 and ctr1 monogenic mutants are also slightly ABA resistant (Beaudoin et al, 2000).…”

“…These observations, in combination with the non-dormant phenotype of the ein2 abi3-4 double mutant indicated that ethylene negatively regulates seed dormancy by inhibiting ABA action (Beaudoin et al, 2000). However, Ghassemian et al, (2000) and Chiwocha et al (2005) showed that, in addition to signalling, the slightly more dormant ethylene insensitive mutants, such as ein2 and etr1-2 have higher ABA levels. The higher levels of germination promoting hormones indicate compensation effects.…”

The Reductase Activity of the Arabidopsis Caleosin RESPONSIVE TO DESSICATION20 Mediates Gibberellin-Dependent Flowering Time, Abscisic Acid Sensitivity, and Tolerance to Oxidative Stress

“…Indeed, these mutants flowered earlier than their control counterparts. Ethylene is also known as a negative regulator of the ABA response during seed germination (Beaudoin et al, 2000;Ghassemian et al, 2000). In agreement with an antagonism between ethylene and oxylipins, lines overexpressing RD20 showed an increased responsiveness to ABA similar to ethylene-insensitive mutants.…”