Novel mechanisms of ethylene-gibberellin crosstalk revealed by the gai eto2-1 double mutant

DELLA proteins have been shown to act as integrators of the signaling network controlling plant growth. In the January issue of New Phytologist (2008), we analyzed the gai eto2-1 double mutant and corresponding single mutants, with defects in the ethylene-biosynthesis and/or in the gibberellin (GA)-signaling cascade. This research revealed yet unknown modes of cross-talk between the ethylene and GA pathways. Two hypotheses have been put forward. Both essentially suggest the existence of reciprocal posttranslational control of ethylene-GA crosstalk

The Arabidopsis mutant eer2 has enhanced ethylene responses in the light

By screening for ethylene response mutants in Arabidopsis, a novel mutant, eer2, was isolated which displays enhanced ethylene responses. On a low nutrient medium (LNM) light-grown eer2 seedlings showed a significant hypocotyl elongation in response to low levels of 1-amino-cyclopropane-1-carboxylate (ACC), the precursor of ethylene, compared with the wild type, indicating that eer2 is hypersensitive to ethylene. Treatment with 1-MCP (1-methylcyclopropene), a competitive inhibitor of ethylene signalling, suppressed this hypersensitive response, demonstrating that it is a bona fide ethylene effect. By contrast, roots of eer2 were less sensitive than the wild type to low concentrations of ACC. The ethylene levels in eer2 did not differ from the wild type, indicating that ethylene overproduction is not the primary cause of the eer2 phenotype. In addition to its enhanced ethylene response of hypocotyls, eer2 is also affected in the pattern of senescence and its phenotype depends on the nutritional status of the growth medium. Furthermore, linkage analysis of eer2 suggests that this mutant defines a new locus in ethylene signalling