The Plant-Specific RAB5 GTPase ARA6 is Required for Starch and Sugar Homeostasis in Arabidopsis thaliana.

Endosomal trafficking plays integral roles in various eukaryotic cell activities. In animal cells, a member of the RAB GTPase family, RAB5, is a key regulator of various endosomal functions. In addition to orthologs of animal RAB5, plants harbor the plant-specific RAB5 group, the ARA6 group, which is conserved in land plant lineages.

Phosphatidylinositol 3-kinase and 4-kinase have distinct roles in intracellular trafficking of cellulose synthase complexes in Arabidopsis thaliana.

The oriented deposition of cellulose microfibrils in the plant cell wall plays a crucial role in various plant functions such as cell growth, organ formation and defense responses. Cellulose is synthesized by cellulose synthase complexes (CSCs) embedded in the plasma membrane (PM), which comprise the cellulose synthases (CESAs). The abundance and localization of CSCs at the PM should be strictly controlled for precise regulation of cellulose deposition, which strongly depends on the membrane trafficking system.