AtAGP30, an arabinogalactan‐protein in the cell walls of the primary root, plays a role in root regeneration and seed germination

Summary Arabinogalactan‐proteins (AGPs) are extracellular proteoglycans that are implicated in many plant growth and developmental processes, but in no case has a biological function been assigned to a particular AGP. AtAGP30 is a non‐classical AGP core protein from Arabidopsis that is expressed only in roots. Analysis of the corresponding mutant, agp30 , has revealed that the wild‐type gene product is required in vitro for root regeneration and in planta for the timing of seed germination. The mutant shows a suppression of the abscisic acid (ABA)‐induced delay in germination and altered expression of some ABA‐regulated genes. This suggests that AtAGP30 functions in the ABA response. By analogy to proteoglycan‐mediated regulation of growth‐factor‐signalling pathways in animals, our data indicate that phytohormone activity in plants can be modulated by AGPs.