Abstract
Crucial roles of endocytosis in various plant functions are emerging recently, but its molecular mechanism and physiological significance still remain largely unknown. Using a model plant, Arabidopsis thaliana, we have been studying the molecular mechanism of endocytosis with a special focus on Rab5 GTPases. Three Rab5 members, ARA7, RHA1 and ARA6, are encoded in the Arabidopsis genome, which are all involved in endocytosis. ARA7 and RHA1 are orthologs of mammalian Rab5, and ARA6 is a plant-unique type of Rab5 member. Through genetic analysis, we have found that these two subgroups function antagonistically in various developmental stages, although they are all activated by the practically sole GEF, VPS9a. Bryophytes and lycophytes also have the ARA6-type Rab5, thus this subgroup is well conserved among land plants. These data indicate that land plants have evolved a quite unique mechanism for the regulation of endocytosis, which is essential for the plant life.
