Endosidin20 does not affect cellulose synthase complex transport from ER to the Golgi.

Cellulose, as the main component of the plant cell wall, is synthesized by plasma membrane-embedded cellulose synthase (CESA) complexes (CSCs). We recently reported a new CESA inhibitor named Endosidin20 (ES20) that targets the catalytic site of CESA6 in Arabidopsis (Arabidopsis thaliana). We found that inhibiting CESA catalytic activity by ES20 treatment reduces the motility of CSC at the plasma membrane and reduces the delivery of CSC to the plasma membrane. We also found that ES20 treatment causes an increased abundance of CSC at the Golgi. Through further investigation, here we show that inhibiting CESA catalytic activity by ES20 treatment does not interfere with the transport of CSC from endoplasmic reticulum (ER) to the Golgi, indicating that inhibiting CESA catalytic activity reduces efficient CSC exit from Golgi. We also show that ES20 affects CSC trafficking without interfering with the trafficking of other cargo proteins in the secretory pathway and does not disturb the cellular localization of typical organelle marker proteins. In combination with our recent findings, our results show that inhibiting CESA catalytic activity by short-term ES20 treatment affects CSC exit from Golgi and CSC post-Golgi transport but does not affect CSC transport from ER to the Golgi.