RNA interference unveils the importance of Pseudotrichonympha grassii cellobiohydrolase, a protozoan exoglucanase, in termite cellulose degradation.

Based on prior work, a cellulase from glycosyl hydrolase family 7 (GHF7) was identified and found to be expressed at a high level in Coptotermes formosanus. To determine the function of GHF7 family members in vivo, we used RNA interference (RNAi) to functionally analyse the exoglucanase gene Pseudotrichonympha grassii cellobiohydrolase gene (PgCBH), which was highly expressed in Pseudotrichonympha grassii, a flagellate found in the hindgut of C. formosanus. In this study, the expression level of PgCBH was down-regulated by RNAi, causing the death of P. grassii, but no effect was observed for other flagellates found in C. formosanus. RNAi also resulted in significantly reduced exoglucanase activity, and no effect was observed for endoglucanase and ß-glucosidase activities. This result demonstrated that the PgCBH gene plays a role in the protist lignocellulolytic process and is also important for host survival. PgCBH can be used as a target gene and has potential as a bioinsecticide for use against termites.

The GH26 ß-mannanase RsMan26H from a symbiotic protist of the termite Reticulitermes speratus is an endo-processive mannobiohydrolase: heterologous expression and characterization.

Symbiotic protists in the gut of termites are prominent natural resources for enzymes involved in lignocellulose degradation. Here we report expression, purification, and biochemical characterization of a glycoside hydrolase family 26 mannanase RsMan26H from the symbiotic protist of the lower termite, Reticulitermes speratus. Biochemical analysis of RsMan26H demonstrates that this enzyme is an endo-processive mannobiohydrolase producing mannobiose from oligo- and polysaccharides, followed by a minor accumulation of oligosaccharides larger than mannobiose. To our knowledge, this is the first report describing the unique mannobiohydrolase enzyme from the eukaryotic origin.

Protein arginine methylation in parasitic protozoa.

Protozoa constitute the earliest branch of the eukaryotic lineage, and several groups of protozoans are serious parasites of humans and other animals. Better understanding of biochemical pathways that are either in common with or divergent from those of higher eukaryotes is integral in the defense against these parasites. In yeast and humans, the posttranslational methylation of arginine residues in proteins affects myriad cellular processes, including transcription, RNA processing, DNA replication and repair, and signal transduction. The protein arginine methyltransferases (PRMTs) that catalyze these reactions, which are unique to the eukaryotic kingdom of organisms, first become evident in protozoa. In this review, we focus on the current understanding of arginine methylation in multiple species of parasitic protozoa, including Trichomonas, Entamoeba, Toxoplasma, Plasmodium, and Trypanosoma spp., and discuss how arginine methylation may play important and unique roles in each type of parasite. We mine available genomic and transcriptomic data to inventory the families of PRMTs in different parasites and the changes in their abundance during the life cycle. We further review the limited functional studies on the roles of arginine methylation in parasites, including epigenetic regulation in Apicomplexa and RNA processing in trypanosomes. Interestingly, each of the parasites considered herein has significantly differing sets of PRMTs, and we speculate on the importance of this diversity in aspects of parasite biology, such as differentiation and antigenic variation.

Systematic position of Histomonas meleagridis based on four protein genes.

Phylogenetic trees based on parabasalid sequences of the small subunit rRNA placed Histomonas meleagridis in close proximity to Dientamoeba fragilis, Tritrichomonas foetus, and Monocercomonas sp. In this study, we sequenced partial genes of glyceraldehyde-3-phosphate dehydrogenase (GAPDH), enolase, and alpha-tubulin from 2 strains of H. meleagridis. We found 5 different GAPDH sequences, 6 different enolase sequences, and 3 alpha-tubulin sequences. Phylogenetic trees based on the obtained sequences showed a close relationship of H. meleagridis with T. foetus and, to some extent, Monocercomonas sp. In conclusion, our findings further corroborate the ssu rRNA-based tree. Consequently, our study also supports the hypothesis that H. meleagridis secondarily lost cytoskeletal structures.