DELLA protein direct targets in Arabidopsis

The aim of this study is to identify early DELLA protein-responsive genes using a Dexamethasone (DEX)-inducible system. Two transgenic lines were used: one induces the expression of a dominant, gibberellin non-responsive DELLA protein (rga-delta17); the other is a control line that carries the same vector, but lacks the rga-delta17 transgene. By comparing the gene expression changes in the line that expresses the rga-delta17 protein in the presence or absence of DEX it is possible to identify putative targets of DELLA proteins. An empty vector transgenic line was included in this study to identify genes that might be regulated by the DEX inducible system that are not dependent on the DELLA protein. Keywords: Dexamethasone treatment, gibberellin treatment, time course, transgene effect Seedlings of both transgenic lines were pretreated for 16 h with 2 uM GA4 to enhance gibberellin responses. Because DELLA proteins are strong signaling repressors, this pretreatment should maximize the effect of DELLA induction. Eight-day old seedlings were treated with 2 uM GA4 or a combination of 2 uM GA4 plus 10 uM DEX to induce the rga-delta17 transgene. Three biological replicas for the transgenic line that carries the DEX-inducible rga-delta17 transgene were generated at 2h and 4h. For the empty vector line, only 2 biological replicas were generated at 4h of treatment with 2 uM GA with or without 10 uM DEX.