Body and organ size in multicellular organisms is governed by intrinsic mechanisms that coordinate cell size and number during development. On , Torii and co-workers describe how three related receptor-like kinases interact synergistically to link cell proliferation to organ growth and flower development in Arabidopsis. Plants that lack ERECTA, a leucine-rich receptor-like serine/threonine kinase, have compact influorescences and short lateral organs, which indicates that ERECTA mediates cell-cell signals that coordinate organ growth. However, a dominant-negative fragment of ERECTA has previously been shown to enhance the phenotype of null erecta plants,so there may be redundancy in the ERECTA signalling pathway. Torii and colleagues now identify two paralogous ERECTA-like receptors – ERL1 and ERL2. erl1 and erl2 mutations alone had no detectable phenotype but each enhanced the defects seen in erecta plants; loss of all three genes severely reduced cell proliferation, resulting in extreme dwarfism and abnormal flower development.
