Swarup R, Perry P, Hagenbeek D, Van Der Straeten D, Beemster GTS, Sandberg G, Bhalerao R, Ljung K, Bennett MJ
Ethylene upregulates auxin biosynthesis in Arabidopsis seedlings to enhance inhibition of root cell elongation
The Plant Cell: 2007 19: 2186-2196

Abstract
Ethylene represents an important regulatory signal for rootdevelopment. Genetic studies in Arabidopsis thaliana have demonstratedthat ethylene inhibition of root growth involves another hormonesignal, auxin. This study investigated why auxin was requiredby ethylene to regulate root growth. We initially observed thatethylene positively controls auxin biosynthesis in the rootapex. We subsequently demonstrated that ethylene-regulated rootgrowth is dependent on (1) the transport of auxin from the rootapex via the lateral root cap and (2) auxin responses occurringin multiple elongation zone tissues. Detailed growth studiesrevealed that the ability of the ethylene precursor 1-aminocyclopropane-1-carboxylicacid to inhibit root cell elongation was significantly enhancedin the presence of auxin. We conclude that by upregulating auxinbiosynthesis, ethylene facilitates its ability to inhibit rootcell expansion.

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