MicroRNAs (miRNAs) are a class of small noncoding RNAs that have important regulatory roles in multicellular organisms. However, miRNA has never been identified experimentally in protist. Direct cloning of 438 expressed miRNA tags by microRNA serial analysis of gene expression from the parasitic protist Trichomonas vaginalis identified nine candidate miRNAs. Bioinformatics analysis of the corresponding genomic region revealed that these miRNA candidates contain a classical stem-loop-stem structure of pre-microRNAs. Analysis of the 20 nt long mature tva-miR-001 showed that it is an intergenic miRNA located at the scaffold DS113596. Tva-miR-001 was differentially expressed in the trophozoite, pseudocyst and amoeboid stages. Based on the experimental results of the present study, we provided solid evidence that protist possesses a miRNA regulating network comparable with multicellular organisms for the first time.

This study explores the effects of an Asian dust storm (ADS) and Southeast Asian biomass burning on the composition of atmospheric aerosols in the coastal area of southern Taiwan in spring 2010. Coarse and fine particles were collected using two manual dichotomous samplers (Dichots) that were equipped with Teflon and Quartz filters. The results reveal that the concentrations of PM 10 and PM 2.5 in the ADS period were about twice those before and after this. More than half of water-soluble ions in coarse particles (PM 2.5-10 ) were Cl -and Na + (sea salt), while 70% of water-soluble ions of fine particles were SO 4 2-and NH 4 + (secondary aerosols). The OC/EC ratios of PM 2.5 and PM 2.5-10 were all above 2.0. Over 98% of the metals in coarse and fine particles were crustal elements (98.1-99.1%), and over 60% of the metals in PM 10 were in coarse particles (PM 2.5-10 ). The water-soluble ion, EC, OC, and metal contents in PM 2.5 all exceeded those in PM 2.5-10 . The ADS was associated with higher concentrations of water-soluble ions in PM 2.5 and PM 2.5-10 than was the non-ADS period, except for K + in PM 2.5-10 . ADS most increased the Ca 2+ content and concentration, causing a rise in the average concentrations of Ca 2+ in coarse and fine particles by factors of 3.0 and 3.2, respectively. In the ADS period, although the OC and EC concentrations of coarse and fine particles increased, the OC and EC contents in these particles decreased. The ADS period was associated with higher metal contents in coarse and fine particles than the non-ADS period, and the increase in PM 2.5-10 (more than 2%) exceeded that in PM 2.5 . In PM 2.5-10 and PM 2.5 , the Ca and Ni contents increased the most, respectively. In addition, the concentrations of the water-soluble ions, EC, OC, and metals in PM 2.5-10 and PM 2.5 increased, but their contents decreased, while the contents of the other constituents (= total -(water-soluble ions + EC + OC + metals)) in PM 2.5-10 and PM 2.5 increased. It is also found that Southeast Asian biomass burning is related to the deterioration of the air quality of southern Taiwan.

MicroRNAs (miRNAs) are a class of extensively studied RNAi-associated small RNAs that play a critical role in eukaryotic gene regulation. However, knowledge on the miRNA and its regulation in unicellular eukaryotes is very limited. In order to obtain a better understanding on the origin of miRNA regulation system, we used deep-sequencing technology to investigate the miRNA expression pattern in four deep-branching unicellular flagellates: Giardia lamblia, Trichomonas vaginalis, Tritrichomonas foetus, and Pentatrichomonas hominis. In addition to the known miRNAs that have been described in G. lamblia and T. vaginalis, we identified 14 ancient animal miRNA families and 13 plant-specific families. Bioinformatics analysis also identified four novel miRNA candidates with reliable precursor structures derived from mature tRNAs. Our results indicated that miRNAs are likely to be a general feature for gene regulation throughout unicellular and multicellular eukaryotes and some of them may derive from unconventional ncRNAs such as snoRNA and tRNA.

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MicroRNAs are highly conserved small noncoding RNAs that can suppress protein translation through complementary binding to target mRNAs. We used a novel approach to identify miRNA targets in the protist Trichomonas vaginalis by comparing the levels of differentially expressed proteins and genes in the trophozoite and amoeboid stages. We observed that the T. vaginalis malate dehydrogenase (Tv_MDH) gene was upregulated 20-fold in the amoeboid stage, but the protein level was reduced by 4.5-fold. Bioinformatics analysis revealed that the Tv_MDH mRNA contains putative target sites of the miR-1 family. The expression level of endogenous tva-miR-1 in the amoeboid stage was 50-fold higher than in the trophozoite stage. Transfection of trophozoites with tva-miR-1 mimics reduced Tv_MDH protein expression by 60%. Based on these experimental data, we conclude that Tv_MDH is negatively regulated by tva-miR-1. The results of this study demonstrate that a combination of proteomic and transcriptomic approaches is a powerful tool for identifying miRNA targets.