Figure 5. Molecular genetic analysis of root-hair differentiation induced by auxin and ethylene.

(A) Roots of rhd6 seedlings grown for three days on unsupplemented (MS) media, and then transferred to either MS, MS+10 nM IAA, or MS+1 µM ACC and grown for two additional days. Arrows indicate the position of root tip at time of transfer. Scale bar: 200 µm (B) Quantitative analysis of root epidermal cell specification in rhd6 seedlings grown for three days on unsupplemented (MS) media, and then transferred to either MS, MS+10 nM IAA, or MS+1 µM ACC and grown for two additional days. The root-hair and non-hair cell types were determined from the portion of the root produced in the last two days. (C) Core root epidermal genes significantly affected (>2-fold change; <0.5% FDR) by transfer of rhd6 WER::GFP seedlings to either MS+10 nM IAA, or MS+1 µM ACC (relative to transfer to MS). After two days of seedling growth on the transferred media, root epidermal cells were collected by GFP-based cell sorting and the RNA used for ATH1 microarray analysis. (D) Plot of the fold-change for the 90 root epidermal genes induced by IAA and by ACC following transfer of rhd6 WER::GFP seedlings to either MS+10 nM IAA, or MS+1 µM ACC. (E) Hierarchical clustering of 208 core root epidermal genes based on their transcript levels on ATH1 chips (triplicate biological replicates) using RNA from developing root epidermal cells in rhd6 WER::GFP seedlings grown for three days on unsupplemented (MS) media, and then transferred to either MS, MS+10 nM IAA, or MS+1 µM ACC and grown for two additional days. Red = high transcript level; Blue = low transcript level. Asterisks indicate genes significantly affected by the hormone treatments.