Fig. 4.

The RSL4-GTL1 module in the gene regulatory network for root hair development. Both environmental signals and developmental signals affect RSL4 expression. Whether environmental signals affect GTL1 expression is not clear but GTL1 is induced by programed developmental signals. RSL4 promotes expression of its own, GTL1 and genes involved in root hair growth. GTL1 counteracts with RSL4 by suppressing expression of RSL4, expression of its own and its downstream targets. This RSL4-GTL1 module might function as a modulator that integrates developmental signals and environmental signals to coordinate root hair growth. Transcriptional activation and repression are indicated by arrows and blunted lines, respectively