Association between physical activity levels and anxiety or depression among college students in China during the COVID-19 pandemic: A meta-analysis.

BACKGROUND: This meta-analysis aimed to investigate the links between the level of physical activity and the risk of anxiety or depression among college students in China during the Coronavirus Disease 2019 pandemic. METHODS: Eligible studies were searched from the PubMed, Embase, and Web of Science databases. The associations between them were assessed with odd ratio (OR) and 95% confidence interval (CI). The heterogeneity of the included studies was evaluated and subgroup analysis was performed. Sensitivity analysis was executed using leave-one-out method. Publication bias of included studies was evaluated. Ten studies with moderate quality were included. RESULTS: Physical activity levels of college students were associated with reduced risk of depression (OR [95%CI] = 0.69 [0.58, 0.82], P < .001) and anxiety (OR [95%CI] = 0.71 [0.62, 0.80], P < .001). The measurement scale of depression or anxiety and whether multi-factor correction was performed or not did not influence the pooled results. The pooled results of depression and anxiety were stable and were not significantly influenced by a single study. No publication bias was observed in the included studies reporting depression and anxiety. CONCLUSION: The physical activity level of college students is negatively correlated with anxiety and depression in China during the pandemic. During the Coronavirus Disease 2019 pandemic, it is necessary to strengthen the construction of university physical education courses. As an organized form of physical activity, physical education classes are a necessary and effective way to increase physical activity among college students.

Association between appendicular lean mass and chronic obstructive pulmonary disease: epidemiological cross-sectional study and bidirectional Mendelian randomization analysis.

Background: The association of BMI with COPD, and sarcopenia in COPD have been both confirmed by several studies, but research on the relationship and causality of body lean mass and the risk of chronic obstructive pulmonary disease (COPD) remains to be discovered. The purpose of this study was to explore the association between lean mass and COPD risk as well as to further examine the causal relationship in the findings. Methods: Three thousand four hundred fifty-nine participants from NHANES 2013-2018 were included in the epidemiological cross-sectional study to assess the association between relative lean mass and COPD by restricted spline analysis (RCS) and weighted multiple logistic regression. Furthermore, to verify the causality between lean mass and COPD, a two-sample Mendelian randomization (MR) with inverse variance weighting (IVW) method was used to analyze GWAS data from European ancestry. Genetic data from the United Kindom Biobank for appendicular lean mass (450,243 cases) and lung function (FEV1/FVC) (400,102 cases) together with the FinnGen platform for COPD (6,915 cases and 186,723 controls) were used for MR. Results: Weighted multiple logistic regression showed a significant correlation between relative appendicular lean mass and COPD after adjusting for confounders (OR = 0.985, 95% CI: 0.975-0.995). Compared to the lower mass (155.3-254.7) g/kg, the high mass (317.0-408.5) g/kg of appendicular lean apparently decreases the risk of COPD (OR = 0.214, 95% CI: 0.060-0.767). Besides, in the analysis of MR, there was a forward causality between appendicular lean mass and COPD (IVW: OR = 0.803; 95%CI: 0.680-0.949; p = 0.01), with a weak trend of causality to lung function. Conclusion: Our study not only found an inverse association between appendicular lean mass and COPD but also supported a unidirectional causality. This provided possible evidence for further identification of people at risk for COPD and prevention of COPD based on limb muscle exercise and nutritional supplementation to maintain skeletal muscle mass.

High purity and viability cell separation of a bacterivorous jakobid flagellate based on a steep velocity gradient induced soft inertial force.

Cell separation is one of the key limiting factors for precise analysis of non-axenic microbial lab cultures or environmental samples, and it remains a challenge to isolate target cells with high purity and viability via high-throughput cell sorting. During the past decade, hydrodynamic microfluidic platforms have attracted great attention in cell preparation for their high efficiency, robust performance and low cost. Here, we employ the use of a low-velocity sheath flow with high viscosity near the wall and a high-velocity sheath flow with low viscosity on the other side of the sample flow in a soft inertial separation chip. This not only prevents hard interactions between cells and chip walls but, in comparison to previous inertial separation methods, generates a significant increase in deflection of large cells while keeping the small ones in the original flow. We first conducted experiments on a mixture of small and large fluorescent particles (1.0 and 9.9 µm, respectively) and removed over 99% of the small particles. The separation efficiency was then tested on a culture of a bacterivorous jakobid flagellate, Seculamonas ecuadoriensis fed on the live bacterium, Klebsiella sp. Using our microfluidic chip, over 94% of live bacteria were removed while maintaining high jakobid cell viability. For comparison, we also conducted size-based cell sorting of the same culture using flow cytometry, which is widely used as a rapid and automated separation tool. Compared with the latter, our chip showed more than 40% higher separation efficiency. Thus, our device provides high purity and viability for cell separation of a sensitive cell sample (jakobid cells). Potentially, the method can be further used for applications in diagnostics, biological analyses and environmental assessment of mixed microbial samples.

Nonsense-mediated mRNA decay in Tetrahymena is EJC independent and requires a protozoa-specific nuclease.

Nonsense-mediated mRNA decay (NMD) is essential for removing premature termination codon-containing transcripts from cells. Studying the NMD pathway in model organisms can help to elucidate the NMD mechanism in humans and improve our understanding of how this biologically important process has evolved. Ciliates are among the earliest branching eukaryotes; their NMD mechanism is poorly understood and may be primordial. We demonstrate that highly conserved Upf proteins (Upf1a, Upf2 and Upf3) are involved in the NMD pathway of the ciliate, Tetrahymena thermophila. We further show that a novel protozoa-specific nuclease, Smg6L, is responsible for destroying many NMD-targeted transcripts. Transcriptome-wide identification and characterization of NMD-targeted transcripts in vegetative Tetrahymena cells showed that many have exon-exon junctions downstream of the termination codon. However, Tetrahymena may lack a functional exon junction complex (EJC), and the Tetrahymena ortholog of an EJC core component, Mago nashi (Mag1), is dispensable for NMD. Therefore, NMD is EJC independent in this early branching eukaryote.

Multiple Origins of Eukaryotic cox15 Suggest Horizontal Gene Transfer from Bacteria to Jakobid Mitochondrial DNA.

The most gene-rich and bacterial-like mitochondrial genomes known are those of Jakobida (Excavata). Of these, the most extreme example to date is the Andalucia godoyi mitochondrial DNA (mtDNA), including a cox15 gene encoding the respiratory enzyme heme A synthase (HAS), which is nuclear-encoded in nearly all other mitochondriate eukaryotes. Thus cox15 in eukaryotes appears to be a classic example of mitochondrion-to-nucleus (endosymbiotic) gene transfer, with A. godoyi uniquely retaining the ancestral state. However, our analyses reveal two highly distinct HAS types (encoded by cox15-1 and cox15-2 genes) and identify A. godoyi mitochondrial cox15-encoded HAS as type-1 and all other eukaryotic cox15-encoded HAS as type-2. Molecular phylogeny places the two HAS types in widely separated clades with eukaryotic type-2 HAS clustering with the bulk of α-proteobacteria (>670 sequences), whereas A. godoyi type-1 HAS clusters with an eclectic set of bacteria and archaea including two α-proteobacteria missing from the type-2 clade. This wide phylogenetic separation of the two HAS types is reinforced by unique features of their predicted protein structures. Meanwhile, RNA-sequencing and genomic analyses fail to detect either cox15 type in the nuclear genome of any jakobid including A. godoyi. This suggests that not only is cox15-1 a relatively recent acquisition unique to the Andalucia lineage but also the jakobid last common ancestor probably lacked both cox15 types. These results indicate that uptake of foreign genes by mtDNA is more taxonomically widespread than previously thought. They also caution against the assumption that all α-proteobacterial-like features of eukaryotes are ancient remnants of endosymbiosis.

Missing genes, multiple ORFs, and C-to-U type RNA editing in Acrasis kona (Heterolobosea, Excavata) mitochondrial DNA.

Discoba (Excavata) is an ancient group of eukaryotes with great morphological and ecological diversity. Unlike the other major divisions of Discoba (Jakobida and Euglenozoa), little is known about the mitochondrial DNAs (mtDNAs) of Heterolobosea. We have assembled a complete mtDNA genome from the aggregating heterolobosean amoeba, Acrasis kona, which consists of a single circular highly AT-rich (83.3%) molecule of 51.5 kb. Unexpectedly, A. kona mtDNA is missing roughly 40% of the protein-coding genes and nearly half of the transfer RNAs found in the only other sequenced heterolobosean mtDNAs, those of Naegleria spp. Instead, over a quarter of A. kona mtDNA consists of novel open reading frames. Eleven of the 16 protein-coding genes missing from A. kona mtDNA were identified in its nuclear DNA and polyA RNA, and phylogenetic analyses indicate that at least 10 of these 11 putative nuclear-encoded mitochondrial (NcMt) proteins arose by direct transfer from the mitochondrion. Acrasis kona mtDNA also employs C-to-U type RNA editing, and 12 homologs of DYW-type pentatricopeptide repeat (PPR) proteins implicated in plant organellar RNA editing are found in A. kona nuclear DNA. A mapping of mitochondrial gene content onto a consensus phylogeny reveals a sporadic pattern of relative stasis and rampant gene loss in Discoba. Rampant loss occurred independently in the unique common lineage leading to Heterolobosea + Tsukubamonadida and later in the unique lineage leading to Acrasis. Meanwhile, mtDNA gene content appears to be remarkably stable in the Acrasis sister lineage leading to Naegleria and in their distant relatives Jakobida.

Cd-metallothioneins in three additional tetrahymena species: intragenic repeat patterns and induction by metal ions.

Ciliate metallothioneins (MTs) possess many unique features compared to the "classic" MTs in other organisms, but they have only been studied in a small number of species. In this study, we investigated cDNAs encoding subfamily 7a metallothioneins (CdMTs) in three Tetrahymena species (T. hegewischi, T. malaccensis, and T. mobilis). Four CdMT genes (ThegMT1, ThegMT2, TmalMT1, and TmobMT1) were cloned and characterized. They share high sequence similarity to previously identified subfamily 7a MT members. Tetrahymena CdMTs exhibit a remarkably regular intragenic repeat homology. The CdMT sequences were divided into two main types of modules, which had been previously described, and which we name "A" and "B". ThegMT2 was identified as the first MT isoform solely composed of module "B". A phylogenetic analysis of individual modules of every characterized Tetrahymena CdMT rigorously documents the conclusion that modules are important units of CdMT evolution, which have undergone frequent and rapid gain/loss and shuffling. The transcriptional activity of the four newly identified genes was measured under different heavy metal exposure (Cd, Cu, Zn, Pb) using real-time quantitative PCR. The results showed that these genes were differentially induced after short (1 h) or long (24 h) metal exposure. The evolutionary diversity of Tetrahymena CdMTs is further discussed with regard to their induction by metal ions.

A P450 gene associated with robust resistance to DDT in ciliated protozoan, Tetrahymena thermophila by efficient degradation.

Analysis of metabolic mechanisms of dichlorodiphenyltrichloroethane (DDT) accumulation and degradation in microorganisms, which could be used to reduce its hazard to higher organisms at the higher in the food chain, have not been investigated. Robust resistance to DDT (grows well in 256 mg/L DDT) and a surprising ability to degrade DDT (more than 70% DDT within 4h) were found in the ciliated protozoan Tetrahymena thermophila. A P450 gene (CYP5013C2) was found to respond specifically to DDT treatment. In the presence of 256 mg/L DDT, cells with overexpressing CYP5013C2 (p450-OE) grew faster and degraded DDT more efficiently than wild-type (WT) cells, while cells with CYP5013C2 partially knocked down (p450-KD) grew slower and exhibited reduced ability to degrade DDT compared to WT cells. Both dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD) were detected in cells after exposure to DDT, and the concentration of DDD in the p450-OE strain gradually decreased from 0.5 to 4h. Thus, we argue that this P450 gene (CYP5013C2), by efficiently degrading DDT to DDD, is associated with robust resistance to DDT in Tetrahymena, and that a strain overexpressing this gene has the potential to serve as bioreactor that degrades environmental DDT.

An alternative root for the eukaryote tree of life.

The root of the eukaryote tree of life defines some of the most fundamental relationships among species. It is also critical for defining the last eukaryote common ancestor (LECA), the shared heritage of all extant species. The unikont-bikont root has been the reigning paradigm for eukaryotes for more than 10 years but is becoming increasingly controversial. We developed a carefully vetted data set, consisting of 37 nuclear-encoded proteins of close bacterial ancestry (euBacs) and their closest bacterial relatives, augmented by deep sequencing of the Acrasis kona (Heterolobosea, Discoba) transcriptome. Phylogenetic analysis of these data produces a highly robust, fully resolved global phylogeny of eukaryotes. The tree sorts all examined eukaryotes into three megagroups and identifies the Discoba, and potentially its parent taxon Excavata, as the sister group to the bulk of known eukaryote diversity, the proposed Neozoa (Amorphea + Stramenopila+Alveolata+Rhizaria+Plantae [SARP]). All major alternative hypotheses are rejected with as little as ∼50% of the data, and this resolution is unaffected by the presence of fast-evolving alignment positions or distant outgroup sequences. This "neozoan-excavate" root revises hypotheses of early eukaryote evolution and highlights the importance of the poorly studied Discoba for understanding the evolution of eukaryotic diversity and basic cellular processes.

Tetrahymena functional genomics database (TetraFGD): an integrated resource for Tetrahymena functional genomics.

The ciliated protozoan Tetrahymena thermophila is a useful unicellular model organism for studies of eukaryotic cellular and molecular biology. Researches on T. thermophila have contributed to a series of remarkable basic biological principles. After the macronuclear genome was sequenced, substantial progress has been made in functional genomics research on T. thermophila, including genome-wide microarray analysis of the T. thermophila life cycle, a T. thermophila gene network analysis based on the microarray data and transcriptome analysis by deep RNA sequencing. To meet the growing demands for the Tetrahymena research community, we integrated these data to provide a public access database: Tetrahymena functional genomics database (TetraFGD). TetraFGD contains three major resources, including the RNA-Seq transcriptome, microarray and gene networks. The RNA-Seq data define gene structures and transcriptome, with special emphasis on exon-intron boundaries; the microarray data describe gene expression of 20 time points during three major stages of the T. thermophila life cycle; the gene network data identify potential gene-gene interactions of 15 049 genes. The TetraFGD provides user-friendly search functions that assist researchers in accessing gene models, transcripts, gene expression data and gene-gene relationships. In conclusion, the TetraFGD is an important functional genomic resource for researchers who focus on the Tetrahymena or other ciliates. Database URL: http://tfgd.ihb.ac.cn/

Transcriptome analysis of the model protozoan, Tetrahymena thermophila, using Deep RNA sequencing.

BACKGROUND: The ciliated protozoan Tetrahymena thermophila is a well-studied single-celled eukaryote model organism for cellular and molecular biology. However, the lack of extensive T. thermophila cDNA libraries or a large expressed sequence tag (EST) database limited the quality of the original genome annotation. METHODOLOGY/PRINCIPAL FINDINGS: This RNA-seq study describes the first deep sequencing analysis of the T. thermophila transcriptome during the three major stages of the life cycle: growth, starvation and conjugation. Uniquely mapped reads covered more than 96% of the 24,725 predicted gene models in the somatic genome. More than 1,000 new transcribed regions were identified. The great dynamic range of RNA-seq allowed detection of a nearly six order-of-magnitude range of measurable gene expression orchestrated by this cell. RNA-seq also allowed the first prediction of transcript untranslated regions (UTRs) and an updated (larger) size estimate of the T. thermophila transcriptome: 57 Mb, or about 55% of the somatic genome. Our study identified nearly 1,500 alternative splicing (AS) events distributed over 5.2% of T. thermophila genes. This percentage represents a two order-of-magnitude increase over previous EST-based estimates in Tetrahymena. Evidence of stage-specific regulation of alternative splicing was also obtained. Finally, our study allowed us to completely confirm about 26.8% of the genes originally predicted by the gene finder, to correct coding sequence boundaries and intron-exon junctions for about a third, and to reassign microarray probes and correct earlier microarray data. CONCLUSIONS/SIGNIFICANCE: RNA-seq data significantly improve the genome annotation and provide a fully comprehensive view of the global transcriptome of T. thermophila. To our knowledge, 5.2% of T. thermophila genes with AS is the highest percentage of genes showing AS reported in a unicellular eukaryote. Tetrahymena thus becomes an excellent unicellular model eukaryote in which to investigate mechanisms of alternative splicing.

Gene network landscape of the ciliate Tetrahymena thermophila.

BACKGROUND: Genome-wide expression data of gene microarrays can be used to infer gene networks. At a cellular level, a gene network provides a picture of the modules in which genes are densely connected, and of the hub genes, which are highly connected with other genes. A gene network is useful to identify the genes involved in the same pathway, in a protein complex or that are co-regulated. In this study, we used different methods to find gene networks in the ciliate Tetrahymena thermophila, and describe some important properties of this network, such as modules and hubs. METHODOLOGY/PRINCIPAL FINDINGS: Using 67 single channel microarrays, we constructed the Tetrahymena gene network (TGN) using three methods: the Pearson correlation coefficient (PCC), the Spearman correlation coefficient (SCC) and the context likelihood of relatedness (CLR) algorithm. The accuracy and coverage of the three networks were evaluated using four conserved protein complexes in yeast. The CLR network with a Z-score threshold 3.49 was determined to be the most robust. The TGN was partitioned, and 55 modules were found. In addition, analysis of the arbitrarily determined 1200 hubs showed that these hubs could be sorted into six groups according to their expression profiles. We also investigated human disease orthologs in Tetrahymena that are missing in yeast and provide evidence indicating that some of these are involved in the same process in Tetrahymena as in human. CONCLUSIONS/SIGNIFICANCE: This study constructed a Tetrahymena gene network, provided new insights to the properties of this biological network, and presents an important resource to study Tetrahymena genes at the pathway level.

Tetrahymena Gene Expression Database (TGED): a resource of microarray data and co-expression analyses for Tetrahymena.

Tetrahymena thermophila is a model eukaryotic organism. Functional genomic analyses in Tetrahymena present rich opportunities to address fundamental questions of cell and molecular biology. The Tetrahymena Gene Expression Database (TGED; available at http://tged.ihb.ac.cn) is the first expression database of a ciliated protozoan. It covers three major physiological and developmental states: growth, starvation, and conjugation, and can be accessed through a user-friendly web interface. The gene expression profiles and candidate co-expressed genes for each gene can be retrieved using Gene ID or Gene description searches. Descriptions of standardized methods of sample preparation and the opportunity to add new Tetrahymena microarray data will be of great interest to the Tetrahymena research community. TGED is intended to be a resource for all members of the scientific research community who are interested in Tetrahymena and other ciliates.

Genome-wide identification and evolution of ATP-binding cassette transporters in the ciliate Tetrahymena thermophila: A case of functional divergence in a multigene family.

BACKGROUND: In eukaryotes, ABC transporters that utilize the energy of ATP hydrolysis to expel cellular substrates into the environment are responsible for most of the efflux from cells. Many members of the superfamily of ABC transporters have been linked with resistance to multiple drugs or toxins. Owing to their medical and toxicological importance, members of the ABC superfamily have been studied in several model organisms and warrant examination in newly sequenced genomes. RESULTS: A total of 165 ABC transporter genes, constituting a highly expanded superfamily relative to its size in other eukaryotes, were identified in the macronuclear genome of the ciliate Tetrahymena thermophila. Based on ortholog comparisons, phylogenetic topologies and intron characterizations, each highly expanded ABC transporter family of T. thermophila was classified into several distinct groups, and hypotheses about their evolutionary relationships are presented. A comprehensive microarray analysis revealed divergent expression patterns among the members of the ABC transporter superfamily during different states of physiology and development. Many of the relatively recently formed duplicate pairs within individual ABC transporter families exhibit significantly different expression patterns. Further analysis showed that multiple mechanisms have led to functional divergence that is responsible for the preservation of duplicated genes. CONCLUSION: Gene duplications have resulted in an extensive expansion of the superfamily of ABC transporters in the Tetrahymena genome, making it the largest example of its kind reported in any organism to date. Multiple independent duplications and subsequent divergence contributed to the formation of different families of ABC transporter genes. Many of the members within a gene family exhibit different expression patterns. The combination of gene duplication followed by both sequence divergence and acquisition of new patterns of expression likely plays a role in the adaptation of Tetrahymen a to its environment.

Animal silks: their structures, properties and artificial production.

This feature article reviews recent progress in the understanding of the hierarchically organized structures, the perfectly balanced mechanical properties and the structure-property relationship of the natural animal silk fibres, as well as the experimental attempts to fabricate man-made silk fibres by means of wet spinning, dry spinning, electrospinning and transgenosis.

Genome-wide identification and characterization of cytochrome P450 monooxygenase genes in the ciliate Tetrahymena thermophila.

BACKGROUND: Cytochrome P450 monooxygenases play key roles in the metabolism of a wide variety of substrates and they are closely associated with endocellular physiological processes or detoxification metabolism under environmental exposure. To date, however, none has been systematically characterized in the phylum Ciliophora. T. thermophila possess many advantages as a eukaryotic model organism and it exhibits rapid and sensitive responses to xenobiotics, making it an ideal model system to study the evolutionary and functional diversity of the P450 monooxygenase gene family. RESULTS: A total of 44 putative functional cytochrome P450 genes were identified and could be classified into 13 families and 21 sub-families according to standard nomenclature. The characteristics of both the conserved intron-exon organization and scaffold localization of tandem repeats within each P450 family clade suggested that the enlargement of T. thermophila P450 families probably resulted from recent separate small duplication events. Gene expression patterns of all T. thermophila P450s during three important cell physiological stages (vegetative growth, starvation and conjugation) were analyzed based on EST and microarray data, and three main categories of expression patterns were postulated. Evolutionary analysis including codon usage preference, site-specific selection and gene-expression evolution patterns were investigated and the results indicated remarkable divergences among the T. thermophila P450 genes. CONCLUSION: The characterization, expression and evolutionary analysis of T. thermophila P450 monooxygenase genes in the current study provides useful information for understanding the characteristics and diversities of the P450 genes in the Ciliophora, and provides the baseline for functional analyses of individual P450 isoforms in this model ciliate species.

Cloning, characterization, and gene expression analysis of a novel cadmium metallothionein gene in Tetrahymena pigmentosa.

A novel cadmium-inducible metallothionein (MT) gene (Tpig-MT1) was cloned and sequenced from the ciliate Tetrahymena pigmentosa. The number of deduced amino acids is 118. The polypeptide possesses CCC and CC clusters characteristic of typical Tetrahymena Cd-inducible MTs. The structure of Tpig-MT1 is different from the reported Cd-MT in T. pyriformis, T. thermophila and T. pigmentosa. Tpig-MT1 contains two intragenic tandem repeats with 72.9% identity described as Tpig-MT1 (repeat A1) and Tpig-MT1 (repeat A2). The transcriptional response of Tpig-MT1 gene to different heavy metals (Cd, Cu, Zn, Hg, Pb) and oxidative stress (H(2)O(2)) was measured using real-time quantitative PCR. The results showed that the gene was quickly induced (1 h) by the five heavy metals and the order of expression level was Hg>Pb>Cd>Cu>Zn. The induction effect of H(2)O(2) was 5-fold after about 15 min, but soon decreased to a non-significant level (30 min). The genetic diversity of Tetrahymena MT genes is discussed in relation to the unique structure of the Tpig-MT1 gene and other reported Cd-MT isoforms.

Cloning and characterization of a new multi-stress inducible metallothionein gene in Tetrahymena pyriformis.

A new multi-stress-inducible metallothionein (MT) gene isoform has been cloned and characterized from the ciliate Tetrahymena pyriformis. Both the 5'- and 3'-UT regions of the Tp-MT2 gene are very different from the previously reported Tp-MT1 isoform in this organism and from other described MT genes in Tetrahymena pigmentosa and Tetrahymena thermophila. The putative protein sequence of Tp-MT2 contains cysteine clusters with characteristics of the typical Tetrahymena Cd-inducible MT genes. However, the sequence has a special feature of four intragenic tandem repeats within its first half, with a conserved structural pattern x(5/8)CCCx(6)CCx(6)CxCxNCxCCK. To investigate the transcriptional activities of both Tp-MT2 and Tp-MT1 genes toward heavy metals (Cd, Hg, Cu, Zn) and H(2)O(2), the mRNA levels of these two isoforms were evaluated by means of real-time quantitative PCR. Results showed that Tp-MT2 had a higher basal expression level than Tp-MT1 and both genes were induced by Cd, Hg, Cu, and Zn ions after short exposure (1h), although to different extents. Cd was the most effective metal inducer of both two isoforms, but the relative expression level of Tp-MT2 was much lower than that of Tp-MT1. Different expression patterns were also shown between the two genes when treated with Cd over a period of 24h. We suggest that TpMT-1 plays the role of a multi-inducible stress gene, while TpMT-2 may have a more specific function in basal metal homeostasis although it may have undergone a functional differentiation process. The putative functional significance and evolutionary mode of the TpMT-2 isoform are discussed.

The giant zooxanthellae-bearing ciliate Maristentor dinoferus (Heterotrichea) is closely related to folliculinidae.

The small subunit rDNA sequence of Maristentor dinoferus (Lobban, Schefter, Simpson, Pochon, Pawlowski, and Foissner, 2002) was determined and compared with sequences from other Heterotrichea and Karyorelictea. Maristentor resembles Stentor in basic morphology and had been provisionally assigned to Stentoridae. However, our phylogenetic analyses show that Maristentor is more closely related to Folliculinidae. Our results support the creation of a separate family for Maristentor, Maristentoridae n. fam., and also confirm the phylogenetic grouping of Folliculindae, Stentoridae, Blepharismidae, and Maristentoridae, which we informally call 'stentorids'. Maristentor, rather than Stentor itself, appears to be most significant in understanding the origins of folliculinids from their aloricate ancestors. Our analyses suggest continued uncertainty in the exact placement of the root of heterotrichs with this phylogenetic marker.