Dinoflagellate Amphiesmal Dynamics: Cell Wall Deposition with Ecdysis and Cellular Growth

Abstract

Dinoflagellates are a major aquatic protist group with amphiesma, multiple cortical membranous “cell wall” layers that contain large circum-cortical alveolar sacs (AVs). AVs undergo extensive remodeling during cell- and life-cycle transitions, including ecdysal cysts (ECs) and resting cysts that are important in some harmful algal bloom initiation–termination. AVs are large cortical vesicular compartments, within which are elaborate cellulosic thecal plates (CTPs), in thecate species, and the pellicular layer (PL). AV-CTPs provide cellular mechanical protection and are targets of vesicular transport that are replaced during EC-swarmer cell transition, or with increased deposition during the cellular growth cycle. AV-PL exhibits dynamical-replacement with vesicular trafficking that are orchestrated with amphiesmal chlortetracycline-labeled Ca2+ stores signaling, integrating cellular growth with different modes of cell division cycle/progression. We reviewed the dynamics of amphiesma during different cell division cycle modes and life cycle stages, and its multifaceted regulations, focusing on the regulatory and functional readouts, including the coral–zooxanthellae interactions.

Cutting through host autofluorescence: fluorescence lifetime imaging microscopy for visualising intracellular bacteria in Symbiodiniaceae

“…We observed the presence of bacteria in dividing furrows of B. minutum cells at the initiation of the light phase. We hypothesised that the re-organisation of thecal plates during cell division ( Kwok et al , 2023 ) in the dark is likely to result in internalisation of bacteria which is followed by de novo synthesis of the cell wall. The bacterial cells attached to the cell surface near the dividing furrow may become endosymbionts which is supported by the finding of diverse intracellular bacteria in this study.…”

“…Maire et al (2021) found that cell cycling and sampling time influenced the prevalence of bacterial present inside the Symbiodiniaceae, Cladocopium proliferum . The light-driven cell stage transitions between coccoid and motile forms as well as dividing cells involves a shedding of the cell wall and re-organisation of thecal plates ( Wakefield et al , 2000 ; Kwok et al , 2023 ). We hypothesised that the surface-attached bacteria may enter B. minutum cells while they are undergoing cell wall re-organisation.…”

Oleaginous Heterotrophic Dinoflagellates—Crypthecodiniaceae

“…Crypthecodiniaceae members are heterotrophs commonly associated with seaweed [ 12 , 13 ]. As with many epiphytic dinoflagellates, C. cohnii cells formed extracellular exudates [ 75 ] and many cells could not be ‘washed away’, indicating potential forming of a phylloplane-like epiphytic community. It was proposed that the dinoflagellate carbon fixation was substantially underestimated attributed to the exudates [ 76 ], that we also found in Crypthecodiniaceae [ 75 ], which also provide substrate for microbial communities with implications in particulate organic carbon [ 77 ] and nutrient recycling.…”