The enl mutants enhance the irx1 root hair mutant phenotype of Arabidopsis thaliana

The development of root hairs serves as an excellent model to study cell growth using both cytological and genetic approaches. In the past, we have characterized LRX1, an extracellular protein of Arabidopsis consisting of an LRR-domain and a structural extensin domain. LRX1 is specifically expressed in root hairs and lrx1 mutants show severe deficiencies in root hair development. In this work, we describe the characterization of enl (enhancer of lrx1) mutants that were isolated in a visual screen of an ethylmethanesulfonate -mutagenized lrx1 line for plants exhibiting an enhanced lrx1 phenotype. Four recessive enl mutants were analyzed, three of which define new genetic loci involved in root hair development. The mutations at the enl loci and lrx1 result in additive phenotypes in enl/lrx1 double mutants. One enl mutant is affected in the ACTIN2 gene and encodes a protein with a 22 amino acid deletion at the C-terminus. The comparison of molecular and phenotypic data of different actin2 alleles suggests that the truncated ACTIN2 protein is still partially functional.