Southern Australian seaweeds: A promising resource for omega-3 fatty acids.

To assess the suitability of southern-Australian macroalgae as potential marine resources for fatty acids (FA), and in particular polyunsaturated fatty acids (PUFA), analysis of 61 species, comprising of 11 Chlorophyta, 17 Phaeophyceae (Ochrophyta) and 33 Rhodophyta, was conducted. Total fatty acid (TFA) concentrations varied considerably (between 0.6 and 7.8 in % of dry weight (DW)) between species, with on average the highest concentrations being in the Phaeophyceae, then the Chlorophyta, and with the Rhodophyta recording the lowest average concentrations. Results revealed significant differences in the fatty acid profiles of the three algal groups. Most species exhibit high proportions of PUFA in their fatty acid profile and a low ratio of n-6/n-3 PUFA. These properties highlight the potential for southern-Australian macroalgae to be used for these FA in food, animal feed and nutraceutical applications.

Characterization of TtALV2, an essential charged repeat motif protein of the Tetrahymena thermophila membrane skeleton.

Alveolins are a recently described class of proteins common to all members of the superphylum Alveolata that are characterized by conserved charged repeat motifs (CRMs) but whose exact function remains unknown. We have analyzed the smaller of the two alveolins of Tetrahymena thermophila, TtALV2. The protein localizes to dispersed, broken patches arranged between the rows of the longitudinal microtubules. Macronuclear knockdown of Ttalv2 leads to multinuclear cells with no apparent cell polarity and randomly occurring cell protrusions, either by interrupting pellicle integrity or by disturbing cytokinesis. Correct association of TtALV2 with the alveoli or the pellicle is complex and depends on both the termini as well as the charged repeat motifs of the protein. Proteins containing similar CRMs are a dominant part of the ciliate membrane cytoskeleton, suggesting that these motifs may play a more general role in mediating membrane attachment and/or cytoskeletal association. To better understand their integration into the cytoskeleton, we localized a range of CRM-based fusion proteins, which suggested there is an inherent tendency for proteins with CRMs to be located in the peripheral cytoskeleton, some nucleating as filaments at the basal bodies. Even a synthetic protein, mimicking the charge and repeat pattern of these proteins, directed a reporter protein to a variety of peripheral cytoskeletal structures in Tetrahymena. These motifs might provide a blueprint for membrane and cytoskeleton affiliation in the complex pellicles of Alveolata.

Ciliate pellicular proteome identifies novel protein families with characteristic repeat motifs that are common to alveolates.

The pellicles of alveolates (ciliates, apicomplexans, and dinoflagellates) share a common organization, yet perform very divergent functions, including motility, host cell invasion, and armor. The alveolate pellicle consists of a system of flattened membrane sacs (alveoli, which are the defining feature of the group) below the plasma membrane that is supported by a membrane skeleton as well as a network of microtubules and other filamentous elements. We recently showed that a family of proteins, alveolins, are common and unique to this pellicular structure in alveolates. To identify additional proteins that contribute to this structure, a pellicle proteome study was conducted for the ciliate Tetrahymena thermophila. We found 1,173 proteins associated with this structure, 45% (529 proteins) of which represented novel proteins without matches to other functionally characterized proteins. Expression of four newly identified T. thermophila pellicular proteins as green fluorescent protein-fusion constructs confirmed pellicular location, and one new protein located in the oral apparatus. Bioinformatic analysis revealed that 21% of the putative pellicular proteins, predominantly the novel proteins, contained highly repetitive regions with strong amino acid biases for particular residues (K, E, Q, L, I, and V). When the T. thermophila novel proteins were compared with apicomplexan genomic data, 278 proteins with high sequence similarity were identified, suggesting that many of these putative pellicular components are shared between the alveolates. Of these shared proteins, 126 contained the distinctive repeat regions. Localization of two such proteins in Toxoplasma gondii confirmed their role in the pellicle and in doing so identified two new proteins of the apicomplexan invasive structure--the apical complex. Screening broadly for these repetitive domains in genomic data revealed large and actively evolving families of such proteins in alveolates, suggesting that these proteins might underpin the diversity and utility of their unique pellicular structure.