Cellulose synthesis (CS) is conducted by membrane-bound
cellulose synthase complexes (CSCs), containing
cellulose synthases (CesA), that are either arranged in hexagonal structures in higher plants or in linear arrays in most microbial organisms, including dinoflagellates. Dinoflagellates are a major phytoplankton group having linear-type CSCs and internal cellulosic thecal plates (
CTPs) in large cortical vesicles. Immunological study suggested CesA1p were cortically localized to the periphery of
CTPs. During
cyst-to-swarmer transition (TC-S), synchronized peaks of CesA1 transcription, CesA1p expression, CS and
CTP formation occurred in respective order, over 12-16 h, strategically allowing the study of CS regulation and
CTP biogenesis. CesA1-knockdown resulted in 40% reduction in CesA1p level and time required for swarmer cells reappearance.
CTPs were severely malformed with reduced
cellulose content. As
CTPs are deposited in internal organelle, the present study demonstrated dinoflagellate CesA1 ortholog was adapted for non-surface deposition; this is different to paradigm of other CesAps which require plasmamembrane for
cellulose fiber deposition. This pioneer gene-knockdown study demonstrated the requirement of a gene for dinoflagellate cell wall remodeling and proper TC-S, which are prominent in dinoflagellate life-cycles.