Novel receptor kinases involved in growth regulation.

The growth of plant cells involves a constant adjustment of synthesis and rearrangement of cell wall polymers. Recently, three plasma membrane-bound receptor kinases related to CrRLK1 have been shown to be involved in the negative control of cell growth in different contexts. THESEUS1 is activated in mutants deficient for cellulose and may act as a cell wall integrity sensor inhibiting cell elongation. FERONIA is polarly localized in synergid cells of the female gametophyte and is required for growth cessation of compatible pollen tubes and subsequent delivery of sperm cells. AmRLK is involved in the control of the polar conical outgrowth of epidermal cells of Antirrhinum petals. The conservation of both extracellular and kinase domains suggests that the three receptors bind to related ligands and have similar cellular outputs, which may involve the production of reactive oxygen species.