Characterization of cellulosic thecal plates of dinoflagellates

Abstract

Dinoflagellates are a diverse group of unicellular eukaryotic algae. Membrane-bound vesicles lie beneath their plasma membrane, and in thecate species, cellulosic thecal plates (CTPs) are formed within the vesicles and are assembled into a three dimensional structures. These unique cellulosic thecal plates are potential research tools in cell wall study and as bio-inspired nanocomposites. The knowledge of CTPs, however, is very limited. To explore the assembly mechanism of CTPs, their ultrastructure, cellulose and proteins were characterized in this thesis. CTPs were found to consist of at least two layers and possessed with several types of pores. In Lingulodinium polyedrum, the pore structures formation are probably related to the mini holes. Microfibril in CTPs were apparently deposited on different ways in different layers. Fourier Transform Infrared Spectrometry (FTIR) results confirmed the presence of cellulose. In nanoindentation results, thecal plates of Pyrocystis lunula and Prorocentrum micans had comparable hardness but the former had an obvious higher elasticity modulus. Very long fine hydrolyzed cellulose microfibril were obtained and their aspect ratio was comparable to the highest ones reported. A large amount of non-crystalline cellulose was found in CTPs samples. These characteristics of dinoflagellate cellulose implacate a novel cellulose deposition mechanism. Five thecal plate proteins were identified. Two were subjected to N-terminal peptide sequencing and one of them was identified as p43. p43 was only found in thecate species but not in naked species tested. p43 protein level peaked at late G₁ and G₂/M phase. RNA interference (RNAi) technology was first attempted in dinoflagellate for further functional investigation. Most characterization methods were developed for the first time in dinoflagellates. The results disclose new features of dinoflagellate thecal plates and their cellulose, and first give clues on thecal plate proteins, which will benefit subsequent studies on cellulose deposition and pattern formation.

Date of Award	2010
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology