The Activity of a Wall-Bound Cellulase Is Required for and Is Coupled to Cell Cycle Progression in the DinoflagellateCrypthecodinium cohnii     

Abstract

Cellulose synthesis, but not its degradation, is generally thought to be required for plant cell growth. In this work, we cloned a dinoflagellate cellulase gene, dCel1, whose activities increased significantly in G 2 /M phase, in agreement with the significant drop of cellulose content reported previously. Cellulase inhibitors not only caused a delay in cell cycle progression at both the G 1 and G 2 /M phases in the dinoflagellate Crypthecodinium cohnii, but also induced a higher level of dCel1p expression. Immunostaining results revealed that dCel1p was mainly localized at the cell wall. Accordingly, the possible role of cellulase activity in cell cycle progression was tested by treating synchronized cells with exogenous dCelp and purified antibody, in experiments analogous to overexpression and knockdown analyses, respectively. Cell cycle advancement was observed in cells treated with exogenous dCel1p, whereas the addition of purified antibody resulted in a cell cycle delay. Furthermore, delaying the G 2 /M phase independently with antimicrotubule inhibitors caused an abrupt and reversible drop in cellulase protein level. Our results provide a conceptual framework for the coordination of cell wall degradation and reconstruction with cell cycle progression in organisms with cell walls. Since cellulase activity has a direct bearing on the cell size, the coupling between cellulase expression and cell cycle progression can also be considered as a feedback mechanism that regulates cell size.

Cell cycle arrest and biochemical changes accompanying cell death in harmful dinoflagellates following exposure to bacterial algicide IRI-160AA

“…The effects of chemical exposure on cell cycle progression in dinoflagellates have been observed in several other studies383940. For example, Leighfield and Van Dolah39 examined a phosphodiesterase inhibitor, IBMX to determine if cAMP was involved in cell cycle regulation in Alexandrium operculatum .…”

Comparative Transcriptome Analysis of a Toxin-Producing Dinoflagellate Alexandrium catenella and Its Non-Toxic Mutant

“…Cellulases are found in some dinoflagellate species and they are hypothesized to be required for cell cycle progression or cell partitioning during mitosis [43,44]. A previous study reports that the hydrolyzed algal biomass can be utilized as sources of carbon or energy for growth of the algae themselves [45].…”

Major transitions in dinoflagellate evolution unveiled by phylotranscriptomics

“…The function of GH7 enzymes in athecate species has not been studied, but they are likely involved in the metabolism of cellulose or related polysaccharides, which may have been an important precondition for the acquisition of the cellulosic thecal plates. Unlike cellulose breakdown, cellulose biosynthesis in dinoflagellates is not understood at the molecular level (34). We identified three types of algal cellulose synthase (CESA-like) homologs in thecate and athecate dinoflagellates, candidates for elucidating their cellulose biosynthesis (SI Appendix, Table S4).…”

“…Origin of theca coincides with onset of cellulase radiation. The origin of the dinoflagellate theca is intimately linked to the biosynthesis of cellulose, its building material, but investigations into the details of cellulose production in dinoflagellates have been limited to rare ultrastructural and labeling studies (34). Recently, production of a highly expressed cellulase [dCel1 from Glycosyl hydrolase family 7 (GH7)] was shown to be coupled to the cell cycle progression in Crypthecodinium cohnii and was immunolocalized to the cell wall in several dinoflagellates, suggesting an important role in cellulose processing during division (31).…”