Biology Commons^™

To Duckweeds (Landoltia Punctata), Nanoparticulate Copper Oxide Is More Inhibitory Than The Soluble Copper In The Bulk Solution, Jiyan Shi, Aamir D. Abid, Ian M. Kennedy, Krassimira R. Hristova, Wendy K. Silk

Biological Sciences Faculty Research and Publications

CuO nanoparticles (CuO-NP) were synthesized in a hydrogen diffusion flame. Particle size and morphology were characterized using scanning mobility particle sizing, Brunauer–Emmett–Teller analysis, dynamic light scattering, and transmission electron microscopy. The solubility of CuO-NP varied with both pH and presence of other ions. CuO-NP and comparable doses of soluble Cu were applied to duckweeds, Landoltia punctata. Growth was inhibited 50% by either 0.6 mg L⁻¹ soluble copper or by 1.0 mg L⁻¹ CuO-NP that released only 0.16 mg L⁻¹ soluble Cu into growth medium. A significant decrease of chlorophyll was observed in plants stressed by 1.0 …

Prion Formation And Polyglutamine Aggregation Are Controlled By Two Classes Of Genes, Anita L. Manogaran, Joo Y. Hong, Joan Hufana, Jens Tyedmers, Susan Lindquist, Susan W. Liebman

Biological Sciences Faculty Research and Publications

Prions are self-perpetuating aggregated proteins that are not limited to mammalian systems but also exist in lower eukaryotes including yeast. While much work has focused around chaperones involved in prion maintenance, including Hsp104, little is known about factors involved in the appearance of prions. De novo appearance of the [PSI+] prion, which is the aggregated form of the Sup35 protein, is dramatically enhanced by transient overexpression of SUP35 in the presence of the prion form of the Rnq1 protein, [PIN+]. When fused to GFP and overexpressed in [ps2] [PIN+] cells, Sup35 forms fluorescent rings, and cells with these rings bud …

Role Of Baca In Lipopolysaccharide Synthesis, Peptide Transport, And Nodulation By Rhizobium Sp. Strain Ngr234, Silvia Ardissone, Hajime Kobayashi, Kumiko Kambara, Coralie Rummel, K. Dale Noel, Graham C. Walker, William J. Broughton, William J. Deakin

Biological Sciences Faculty Research and Publications

BacA of Sinorhizobium meliloti plays an essential role in the establishment of nitrogen-fixing symbioses with Medicago plants, where it is involved in peptide import and in the addition of very-long-chain fatty acids (VLCFA) to lipid A of lipopolysaccharide (LPS). We investigated the role of BacA in Rhizobium species strain NGR234 by mutating the bacA gene. In the NGR234 bacA mutant, peptide import was impaired, but no effect on VLCFA addition was observed. More importantly, the symbiotic ability of the mutant was comparable to that of the wild type for a variety of legume species. Concurrently, an acpXL mutant of NGR234 …

Effect Of Nitrate, Acetate And Hydrogen On Native Perchlorate-Reducing Microbial Communities And Their Activity In Vadose Soil, Mamie Nozawa-Inoue, Mercy Jien, Kun Yang, Dennis E. Rolston, Krassimira R. Hristova, Kate M. Scow

Biological Sciences Faculty Research and Publications

The effect of nitrate, acetate, and hydrogen on native perchlorate-reducing bacteria (PRB) was examined by conducting microcosm tests using vadose soil collected from a perchlorate-contaminated site. The rate of perchlorate reduction was enhanced by hydrogen amendment and inhibited by acetate amendment, compared with unamendment. Nitrate was reduced before perchlorate in all amendments. In hydrogen-amended and unamended soils, nitrate delayed perchlorate reduction, suggesting that the PRB preferentially use nitrate as an electron acceptor. In contrast, nitrate eliminated the inhibitory effect of acetate amendment on perchlorate reduction and increased the rate and the extent, possibly because the preceding nitrate reduction/denitrification decreased the …

Involvement Of Protein Kinase C And Protein Kinase A In The Enhancement Of L-Type Calcium Current By GabaB Receptor Activation In Neonatal Hippocampus, Jennifer Grace Bray, Michelle Mynlieff

Biological Sciences Faculty Research and Publications

In the early neonatal period activation of GABA_B receptors attenuates calcium current through N-type calcium channels while enhancing current through L-type calcium channels in rat hippocampal neurons. The attenuation of N-type calcium current has been previously demonstrated to occur through direct interactions of the βγ subunits of G_i/o G-proteins, but the signal transduction pathway for the enhancement of L-type calcium channels in mammalian neurons remains unknown. In the present study, calcium currents were elicited in acute cultures from postnatal day 6–8 rat hippocampi in the presence of various modulators of protein kinase A (PKA) and protein kinase C …

Mutational-Kinetic Analysis Reveals The Roles Of Arginines And Aromatics In The Core Of The Gabaa Receptor Ligand-Binding Pocket, Phu Tran

Dissertations (1934 -)

The γ-aminobutyric acid type A (GABA) receptor is a member of the cys-loop family of ligand-gated ion channels that plays a crucial role in normal brain function by transducing the majority of inhibitory neurotransmission in the central nervous system. The studies documented in this dissertation were aimed at validating and refining the current best model for the interaction of GABA with the GABAA receptor via structure-function perturbation analysis. Mutational-kinetic data was used in conjunction with homology modeling knowledge to draw up architectural and functional roles of the arginines and aromatics in GABA-binding pocket. The results provide interesting new insights.

Two …

Exploring The Architecture Of The Human Gaba(A) Receptor Ligand Binding Pocket Via Mutational, Electrophysiological, And Kinetic Analysis, Kurt Thomas Laha

Dissertations (1934 -)

The gamma-aminobutyric acid type A (GABA_A) receptor is a member of the cys-loop family of ligand-gated ion channels, and plays a crucial role in normal brain function by providing inhibitory neurotransmission. The objective of my research is to establish the mechanisms that underlie the interaction between the GABA_A receptor and GABA during binding, as well as to provide direct information about the architecture of the ligand binding pocket. To achieve this, a multitude of amino acid residues surrounding the GABA binding pocket were individually mutated and structure-function relationships were explored. Changes in EC_50-GABA, macroscopic kinetics, …

Effect Of Animal Facility Construction On Basal Hypothalamic-Pituitary-Adrenal And Renin-Aldosterone Activity In The Rat, Hershel Raff, Eric D. Bruder, William E. Cullinan, Dana R. Ziegler, Eric P. Cohen

Biomedical Sciences Faculty Research and Publications

Nearby construction can cause subtle, but important activation of the hypothalamic-pituitary-adrenal axis in laboratory rats.

Although loud noise and intense vibration are known to alter the behavior and phenotype of laboratory animals, little is known about the effects of nearby construction. We studied the effect of a nearby construction project on the classic stress hormones ACTH, corticosterone, renin, and aldosterone in rats residing in a barrier animal facility before, for the first 3 months of a construction project, and at 1 month after all construction was completed. During some of the construction, noise and vibrations were not obvious to investigators …

Community And Ecosystem Ramifications Of Increasing Lianas In Neotropical Forests, Stefan A. Schnitzer, Frans Bongers, S. Joseph Wright

Biological Sciences Faculty Research and Publications

Lianas (woody vines) are increasing in neotropical forests, representing one of the first large-scale structural changes documented for these important ecosystems. The potential ramifications of increasing lianas are huge, as lianas alter both tropical forest diversity and ecosystem functioning. At the community level, lianas affect tree species co-existence and diversity by competing more intensely with some tree species than others, and thus will likely alter tree species composition. At the ecosystem level, lianas affect forest carbon and nutrient storage and fluxes. A decrease in forest carbon storage and sequestration may be the most important ramification of liana increases. Lianas reduce …

Increasing Liana Abundance And Biomass In Tropical Forests: Emerging Patterns And Putative Mechanisms, Stefan A. Schnitzer, Frans Bongers

Biological Sciences Faculty Research and Publications

Tropical forests are experiencing large‐scale structural changes, the most apparent of which may be the increase in liana (woody vine) abundance and biomass. Lianas permeate most lowland tropical forests, where they can have a huge effect on tree diversity, recruitment, growth and survival, which, in turn, can alter tree community composition, carbon storage and carbon, nutrient and water fluxes. Consequently, increasing liana abundance and biomass have potentially profound ramifications for tropical forest composition and functioning. Currently, eight studies support the pattern of increasing liana abundance and biomass in American tropical and subtropical forests, whereas two studies, both from Africa, do …

Soil Microbes Drive The Classic Plant Diversity–Productivity Pattern, Stefan A. Schnitzer, John Klironomos, Janneke Hillerislambers, Linda L. Kinkel, Peter B. Reich, Kun Xiao, Matthias C. Rillig, Benjamin A. Sikes, Ragan M. Callaway, Scott A. Mangan, Egbert H. Van Nes, Marten Scheffer

Biological Sciences Faculty Research and Publications

Ecosystem productivity commonly increases asymptotically with plant species diversity, and determining the mechanisms responsible for this well‐known pattern is essential to predict potential changes in ecosystem productivity with ongoing species loss. Previous studies attributed the asymptotic diversity–productivity pattern to plant competition and differential resource use (e.g., niche complementarity). Using an analytical model and a series of experiments, we demonstrate theoretically and empirically that host‐specific soil microbes can be major determinants of the diversity–productivity relationship in grasslands. In the presence of soil microbes, plant disease decreased with increasing diversity, and productivity increased nearly 500%, primarily because of the strong effect of …

Dominance By The Introduced Tree Rhamnus Cathartica (Common Buckthorn) May Limit Aboveground Carbon Storage In Southern Wisconsin Forests, Joseph Mascaro, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

Many ecosystems are now dominated by introduced species, and because dominant species drive ecosystem properties, these changes lead to increased uncertainty in estimates of carbon storage and cycling. We examined aboveground biomass in forests dominated by the introduced tree Rhamnus cathartica (common buckthorn) relative to forests dominated by native species, and measured aboveground biomass increment over a three-year period (2005–2008). Three of the four lowest biomass levels occurred in R. cathartica-dominated forests, and biomass in these forest types was stored primarily in trees 10–20 cm DBH. By contrast, forests dominated by native trees (including those with R. cathartica understories) …

Coming To America: Multiple Origins Of New World Geckos, Tony Gamble, A. M. Bauer, G. R. Colli, E. Greenbaum, T. R. Jackman, Laurie J. Vitt, Andrew M. Simons

Biological Sciences Faculty Research and Publications

Geckos in the Western Hemisphere provide an excellent model to study faunal assembly at a continental scale. We generated a time-calibrated phylogeny, including exemplars of all New World gecko genera, to produce a biogeographic scenario for the New World geckos. Patterns of New World gecko origins are consistent with almost every biogeographic scenario utilized by a terrestrial vertebrate with different New World lineages showing evidence of vicariance, dispersal via temporary land bridge, overseas dispersal, or anthropogenic introductions. We also recovered a strong relationship between clade age and species diversity, with older New World lineages having more species than more recently …

Neuronal Control Of Swimming Behavior: Comparison Of Vertebrate And Invertebrate Model Systems, Olivia Mullins, John Hackett, James T. Buchanan, W. Otto Friesen

Biological Sciences Faculty Research and Publications

Swimming movements in the leech and lamprey are highly analogous, and lack homology. Thus, similarities in mechanisms must arise from convergent evolution rather than from common ancestry. Despite over 40 years of parallel investigations into this annelid and primitive vertebrate, a close comparison of the approaches and results of this research is lacking. The present review evaluates the neural mechanisms underlying swimming in these two animals and describes the many similarities that provide intriguing examples of convergent evolution. Specifically, we discuss swim initiation, maintenance and termination, isolated nervous system preparations, neural-circuitry, central oscillators, intersegmental coupling, phase lags, cycle periods and …

Mathematical Model Of Chlorella Minutissima Utex2341 Growth And Lipid Production Under Photoheterotrophic Fermentation Conditions, Jinshui Yang, Ehsan Rasa, Prapakorn Tantayotai, Kate M. Scow, Hong Li Yuan, Krassimira R. Hristova

Biological Sciences Faculty Research and Publications

To reduce the cost of algal biomass production, mathematical model was developed for the first time to describe microalgae growth, lipid production and glycerin consumption under photoheterotrophic conditions based on logistic, Luedeking–Piret and Luedeking–Piret-like equations. All experiments were conducted in a 2 L batch reactor without considering CO₂ effect on algae’s growth and lipid production. Biomass and lipid production increased with glycerin as carbon source and were well described by the logistic and Luedeking–Piret equations respectively. Model predictions were in satisfactory agreement with measured data and the mode of lipid production was growth-associated. Sensitivity analysis was applied to examine …

First Record Of Alston's Woolly Mouse Opossum (Micoureus Alstoni) From The Canal Area Of Central Panama, Thomas D. Lambert, Michaela K. Halsey, Jacob W. Dittel, Scott A. Mangan, Erika Delfosse, Gregory H. Adler, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

No abstract provided.

Anolis Chrysolepis Duméril And Bibron, 1837 (Squamata: Iguanidae), Revisited: Molecular Phylogeny And Taxonomy Of The Anolis Chrysolepis Species Group, Annelise B. D'Angiolella, Tony Gamble, Teresa C. S. Avila-Pires, Guarino R. Colli, Brice P. Noonan, Laurie J. Vitt

Biological Sciences Faculty Research and Publications

The Anolis chrysolepis species group is distributed across the entire Amazon basin and currently consists of A. bombiceps and five subspecies of A. chrysolepis. These lizards are characterized by moderate size, relatively narrow digital pads, and a small dewlap that does not reach the axilla. We used the mitochondrial gene ND2 to estimate phylogenetic relationships among putative subspecies of A. chrysolepis and taxa previously hypothesized to be their close relatives. We also assessed the congruence between molecular and morphological datasets to evaluate the taxonomic status of group members. On the basis of the two datasets, we present a new …

Activation And Inhibition Of Pyruvate Carboxylase From Rhizobium Etli, Tonya N. Zeczycki, Ann L. Menefee, Sarawut Jitrapakdee, John C. Wallace, Paul V. Attwood, Martin St. Maurice, W Wallace Cleland

Biological Sciences Faculty Research and Publications

While crystallographic structures of the R. etli pyruvate carboxylase (PC) holoenzyme revealed the location and probable positioning of the essential activator, Mg²⁺, and nonessential activator, acetyl-CoA, an understanding of how they affect catalysis remains unclear. The current steady-state kinetic investigation indicates that both acetyl-CoA and Mg²⁺ assist in coupling the MgATP-dependent carboxylation of biotin in the biotin carboxylase (BC) domain with pyruvate carboxylation in the carboxyl transferase (CT) domain. Initial velocity plots of free Mg²⁺ vs pyruvate were nonlinear at low concentrations of Mg²⁺ and a nearly complete loss of coupling between the BC and …

Contributions Made By Cdc25 Phosphatases To Proliferation Of Intestinal Epithelial Stem And Progenitor Cells, Gwanghee Lee, Sofia Origanti, Lynn S. White, Jinwu Sun, Thaddeus S. Stappenbeck, Helen Piwnica-Worms

Biological Sciences Faculty Research and Publications

The CDC25 protein phosphatases drive cell cycle advancement by activating cyclin-dependent protein kinases (CDKs). Humans and mice encode three family members denoted CDC25A, -B and -C and genes encoding these family members can be disrupted individually with minimal phenotypic consequences in adult mice. However, adult mice globally deleted for all three phosphatases die within one week after Cdc25 disruption. A severe loss of absorptive villi due to a failure of crypt epithelial cells to proliferate was observed in the small intestines of these mice. Because the Cdc25s were globally deleted, the small intestinal phenotype and loss of animal viability could …

Novel Insights Into The Biotin Carboxylase Domain Reactions Of Pyruvate Carboxylase From Rhizobium Etli, Tonya N. Zeczycki, Ann L. Menefee, Abdussalam Adina-Zada, Sarawut Jitrapakdee, Kathy H. Surinya, John C. Wallace, Paul V. Attwood, Martin St. Maurice, W Wallace Cleland

Biological Sciences Faculty Research and Publications

The catalytic mechanism of the MgATP-dependent carboxylation of biotin in the biotin carboxylase domain of pyruvate carboxylase from R. etli (RePC) is common to the biotin-dependent carboxylases. The current site-directed mutagenesis study has clarified the catalytic functions of several residues proposed to be pivotal in MgATP-binding and cleavage (Glu218 and Lys245), HCO3 − deprotonation (Glu305 and Arg301), and biotin enolization (Arg353). The E218A mutant was inactive for any reaction involving the BC domain and the E218Q mutant exhibited a 75-fold decrease in kcat for both pyruvate carboxylation and the full reverse reaction. The E305A mutant also showed a 75- and …

Magnetic Scanometric Dna Microarray Detection Of Methyl Tertiary Butyl Ether Degrading Bacteria For Environmental Monitoring, Mei-Lin Chan, Gerardo Jaramillo, Krassimira R. Hristova, David A. Horsley

Biological Sciences Faculty Research and Publications

A magnetoresistive biosensing platform based on a single magnetic tunnel junction (MTJ) scanning probe and DNA microarrays labeled with magnetic particles has been developed to provide an inexpensive, sensitive and reliable detection of DNA. The biosensing platform was demonstrated on a DNA microarray assay for quantifying bacteria capable of degrading methyl tertiary butyl ether (MTBE), where concentrations as low as 10 pM were detectable. Synthetic probe bacterial DNA was immobilized on a microarray glass slide surface, hybridized with the 48 base pair long biotinylated target DNA and subsequently incubated with streptavidin-coated 2.8 μm diameter magnetic particles. The biosensing platform then …

Hsp70 And Hsp40 Functionally Interact With Soluble Mutant Huntingtin Oligomers In A Classic Atp-Dependent Reaction Cycle, Gregor P. Lotz, Justin Legleiter, Rebecca Aron, Emily M. Sontag, Shao-Yi Huang, Cheping Ng, Charles G. Glabe, Leslie M. Thompson, Paul J. Muchowski

Biological Sciences Faculty Research and Publications

Inclusion bodies of aggregated mutant huntingtin (htt) fragments are a neuropathological hallmark of Huntington disease (HD). The molecular chaperones Hsp70 and Hsp40 colocalize to inclusion bodies and are neuroprotective in HD animal models. How these chaperones suppress mutant htt toxicity is unclear but might involve direct effects on mutant htt misfolding and aggregation. Using size exclusion chromatography and atomic force microscopy, we found that mutant htt fragments assemble into soluble oligomeric species with a broad size distribution, some of which reacted with the conformation-specific antibody A11. Hsp70 associated with A11-reactive oligomers in an Hsp40- and ATP-dependent manner and inhibited their …

Structure And Expression Of Two Nuclear Receptor Genes In Marsupials: Insights Into The Evolution Of The Antisense Overlap Between The Α-Thyroid Hormone Receptor And Rev-Erbα, Brandon C. Rindfleisch, M. Scott Brown, John L. Vandeberg, Stephen Munroe

Biological Sciences Faculty Research and Publications

Background: Alternative processing of α-thyroid hormone receptor (TRα, NR1A1) mRNAs gives rise to two functionally antagonistic nuclear receptors: TRα1, the α-type receptor, and TRα2, a non-hormone binding variant that is found only in mammals. TRα2 shares an unusual antisense coding overlap with mRNA for Rev-erbα (NR1D1), another nuclear receptor protein. In this study we examine the structure and expression of these genes in the gray short-tailed opossum, Monodelphis domestica, in comparison with that of eutherian mammals and three other marsupial species, Didelphis virginiana, Potorous tridactylus and Macropus eugenii, in order to understand the evolution and regulatory …

Drosophila Vitelline Membrane Assembly: A Critical Role For An Evolutionarily Conserved Cysteine In The “Vm Domain” Of Sv23, T. Wu, Anita L. Manogaran, J. M. Beauchamp, Gail L. Waring

Biological Sciences Faculty Research and Publications

The vitelline membrane (VM), the oocyte proximal layer of the Drosophila eggshell, contains four major proteins (VMPs) that possess a highly conserved “VM domain” which includes three precisely spaced, evolutionarily conserved, cysteines (CX⁷CX⁸C). Focusing on sV23, this study showed that the three cysteines are not functionally equivalent. While substitution mutations at the first (C123S) or third (C140S) cysteines were tolerated, females with a substitution at the second position (C131S) were sterile. Fractionation studies showed that sV23 incorporates into a large disulfide linked network well after its secretion ceases, suggesting that post-depositional mechanisms are in place to …

Circadian Disruption And Metabolic Disease: Findings From Animal Models, Deanna M. Arble, Kathryn Moynihan Ramsey, Joseph Bass, Fred W. Turek

Biological Sciences Faculty Research and Publications

Social opportunities and work demands have caused humans to become increasingly active during the late evening hours, leading to a shift from the predominantly diurnal lifestyle of our ancestors to a more nocturnal one. This voluntarily decision to stay awake long into the evening hours leads to circadian disruption at the system, tissue, and cellular levels. These derangements are in turn associated with clinical impairments in metabolic processes and physiology. The use of animal models for circadian disruption provides an important opportunity to determine mechanisms by which disorganization in the circadian system can lead to metabolic dysfunction in response to …

Reversible Deficiencies In Flagellar Beating And Axonemal Assembly, Mei Wei

Dissertations (1934 -)

Axonemal complexes in flagella are largely prepackaged in the cell body. As such, one mutation often results in the absence of the co-assembled components and permanent motility deficiencies. For example, a Chlamydomonas mutant defective in RSP4 in the radial spoke, which is critical for bend propagation, has paralyzed flagella that also lack the paralogue RSP6 and three additional radial spoke proteins. Intriguingly, recent studies showed that several mutant strains contain a mixed population of swimmers and paralyzed cells despite their identical genetic background. Here we report a cause underlying these variations. Two new mutants lacking RSP6 swim processively and other …

Role Of Ampk Throughout Meiotic Maturation In The Mouse Oocyte: Evidence For Promotion Of Polar Body Formation And Suppression Of Premature Activation, Stephen M. Downs, Ru Ya, Christopher C. Davis

Biological Sciences Faculty Research and Publications

This study was conducted to assess the role of AMPK in regulating meiosis in mouse oocytes from the germinal vesicle stage to metaphase II. Exposure of mouse cumulus cell-enclosed oocytes (CEO) and denuded oocytes (DO) during spontaneous maturation in vitro to AMPK-activating agents resulted in augmentation of the rate and frequency of polar body formation. Inhibitors of AMPK had an opposite, inhibitory effect. In addition, the AMPK inhibitor, compound C (Cmpd C) increased the frequency of oocyte activation. The stimulatory action of the AMPK-activating agent, AICAR, and the inhibitory action of Cmpd C were diminished if exposure was delayed, indicating …

Post‐Glacial Expansion Into The Paleozoic Plateau: Evidence Of An Ozarkian Refugium For The Ozark Minnow Notropis Nubilus (Teleostei: Cypriniformes), Peter B. Berendzen, J.F. Dugan, Tony Gamble

Biological Sciences Faculty Research and Publications

Genetic variation was examined within the Ozark minnow Notropis nubilus using complete mtDNA cytochrome b gene sequences from 160 individuals representing 30 localities to test hypotheses on the origin of the distribution. Phylogenetic analyses revealed three strongly supported clades of haplotypes consistent with geographic distributions: a clade from the Western Ozarks, a clade from the Southern Ozarks and a clade from the Northern Ozarks and upper Mississippi River basin. The estimated mean ages of these clades indicated that they diverged during pre-Illinoian glacial cycles extending from the late Pliocene into the early Pleistocene. Results of demographic analyses based on coalescent …

Prolonged Space Flight-Induced Alterations In The Structure And Function Of Human Skeletal Muscle Fibres, Robert H. Fitts, S. W. Trappe, David R. Costill, Philip M. Gallagher, Andrew C. Creer, Patricia A. Colloton, Jim R. Peters, Janell Romatowski, J. L. Bain, Danny A. Riley

Biological Sciences Faculty Research and Publications

The primary goal of this study was to determine the effects of prolonged space flight (~180 days) on the structure and function of slow and fast fibres in human skeletal muscle. Biopsies were obtained from the gastrocnemius and soleus muscles of nine International Space Station crew members ~45 days pre- and on landing day (R+0) postflight. The main findings were that prolonged weightlessness produced substantial loss of fibre mass, force, and power with the hierarchy of the effects being soleus type I > soleus type II > gastrocnemius type I > gastrocnemius type II. Structurally, the quantitatively most important adaptation was fibre atrophy …

Loss Of Individual Micrornas Causes Mutant Phenotypes In Sensitized Genetic Backgrounds In C. Elegans, John L. Brenner, Kristen L. Jasiewicz, Alisha F. Fahley, Benedict J. Kemp, Allison L. Abbott

Biological Sciences Faculty Research and Publications

MicroRNAs (miRNAs) are small, noncoding RNAs that regulate the translation and/or stability of their mRNA targets. Previous work showed that for most miRNA genes of C. elegans, single-gene knockouts did not result in detectable mutant phenotypes. This may be due, in part, to functional redundancy between miRNAs. However, in most cases, worms carrying deletions of all members of a miRNA family do not display strong mutant phenotypes. They may function together with unrelated miRNAs or with non-miRNA genes in regulatory networks, possibly to ensure the robustness of developmental mechanisms. To test this, we examined worms lacking individual miRNAs in …