Membrane trafficking mediated by OsDRP2B is specific for cellulose biosynthesis.

Increasing evidence has revealed that membrane trafficking is highly associated with cell wall metabolism. Factors involved in vesicle delivery, e.g. cytoskeleton and motor proteins, have showed regulatory effects on cell wall structure and components. However, little is known about the involvement of other trafficking components in distribution of cell wall-related compartments. Dynamins are important proteins functioning in membrane tubulation and vesiculation. Recently, we have reported characterization of the rice dynamin-related protein 2B (OsDRP2B). Mutation in OsDRP2B causes a significant reduction in cellulose content. Its association with the trans-Golgi network (TGN) and clathrin-coated vesicles and the reduced CESA4 abundance at the bc3 plasma membrane suggest that BC3/OsDRP2B is involved in the transport of essential elements for cellulose synthesis. Here, we provide additional evidence for BC3 subcellular localization via observing OsDRP2B-GFP in living root hairs of transgenic plants. Uronic acid and fractional composition analyses further confirm that the amount of arabinoxylan and other noncellulosic polysaccharides is increased in bc3. However, three putative xylan synthesis genes are down-regulated in mutant plant revealed by real-time PCR analysis. These results imply that compartments delivered by OsDRP2B are specifically responsible for cellulose biosynthesis.