Receptor serine/threonine protein kinases in signalling: analysis of the erecta receptor-like kinase of Arabidopsis thaliana

The Arabidopsis ERECTA (ER) gene regulates elongation of above-ground organ s. ER encodes a member of the leucine-rich repeats-receptor-like protein ki nases (LRR-RLK) gene family, with the predicted protein containing a signal peptide, 20 leucine-rich repeats in the extracellular domain, a transmembr ane domain, and a cytoplasmic serine/threonine protein kinase domain. The s tructural features of the predicted ER protein suggest its role in cell-cel l signalling is through phosphorylating serine/threonine residues. Consiste nt with this hypothesis, in vitro protein kinase analysis indicates that ER is a functional serine/threonine protein kinase. Furthermore, a large-scal e genetic screen was conducted to analyse new mutations in the erecta gene; 16 new er alleles were isolated, all of which were recessive. Here we pres ent the identification of molecular lesions of seven alleles of er, which s uggests the hypothesis that ERECTA might employ a mode of action distinct f rom other RLKs such as Xa21 or CLAVATA1, which function in disease resistan ce and developmental pathways, respectively. (C) New Phytologist (2001) 151 : 133-143.