An expanded auxin-inducible degron toolkit for Caenorhabditis elegans

The mIAA7 degron improves auxin-mediated degradation in Caenorhabditiselegans

Auxin-inducible degradation is a powerful tool for the targeted degradation of proteins with spatiotemporal control. One limitation of the auxin-inducible degradation system is that not all proteins are degraded efficiently. Here, we demonstrate that an alternative degron sequence, termed mIAA7, improves the efficiency of degradation in Caenorhabditiselegans, as previously reported in human cells. We tested the depletion of a series of proteins with various subcellular localizations in different tissue types and found that the use of the mIAA7 degron resulted in faster depletion kinetics for 5 out of 6 proteins tested. The exception was the nuclear protein HIS-72, which was depleted with similar efficiency as with the conventional AID* degron sequence. The mIAA7 degron also increased the leaky degradation for 2 of the tested proteins. To overcome this problem, we combined the mIAA7 degron with the C. elegans AID2 system, which resulted in complete protein depletion without detectable leaky degradation. Finally, we show that the degradation of ERM-1, a highly stable protein that is challenging to deplete, could be improved further by using multiple mIAA7 degrons. Taken together, the mIAA7 degron further increases the power and applicability of the auxin-inducible degradation system. To facilitate the generation of mIAA7-tagged proteins using CRISPR/Cas9 genome engineering, we generated a toolkit of plasmids for the generation of dsDNA repair templates by PCR.

Continuous double-strand break induction and their differential processing sustain chiasma formation during Caenorhabditis elegans meiosis

Faithful chromosome segregation into gametes depends on Spo11-induced DNA double-strand breaks (DSBs). These yield single-stranded 3' tails upon resection to promote crossovers (COs). While early Mre11-dependent end resection is the predominant pathway in most organisms, Exo1 or Dna2/BLM can also contribute to the efficient processing of meiotic DSBs. Although its enzymatic activity has been thoroughly dissected, the temporal dynamics underlying Spo11 activity have remained mostly elusive. We show that, in Caenorhabditis elegans, SPO-11-mediated DSB induction takes place throughout early meiotic prophase I until mid-late pachynema. We find that late DSBs are essential for CO formation and are preferentially processed by EXO-1 and DNA-2 in a redundant fashion. Further, EXO-1-DNA-2-mediated resection ensures completion of conservative DSB repair and discourages activation of KU-dependent end joining. Taken together, our data unveil important temporal aspects of DSB induction and identify previously unknown functional implications for EXO-1-DNA-2-mediated resection activity in C. elegans.

A simple strategy for addition of degron tags to endogenous genes harboring prior insertions of fluorescent protein

There exist insufficient validated "entry portal" sites in the C. elegans genome for CRISPR/Cas9-dependent insertion into endogenous genes to confer diverse spatiotemporal patterns and levels of expression on exogenous sequences. Consequently, we recognized the most common potential "entry portal" sequences: genes previously tagged with fluorescent proteins using CRISPR/Cas9. As proof of concept, we used existing mKate2-encoding sequences inserted in the 5' end of genes as an insertion point for the auxin inducible degron, AID*. This sequence permits reasonably efficient insertion that can be employed using a variety of approaches for different end goals. Our strategy is thus generalizable to many needs.

A new toolkit to visualize and perturb endogenous LIN-12/Notch signaling in C. elegans

Notch signaling mediates cell-cell interactions during development and homeostasis. Methods for visualizing and manipulating Notch activity in vivo are essential to elucidate how the Notch pathway functions. Here, we provide new tools for use in C. elegans to visualize and perturb Notch signaling in vivo using endogenously tagged alleles of the Notch receptor lin-12 . Tagging the endogenous LIN-12 intracellular domain with the fluorescent protein mNeonGreen (mNG) allowed for visualization of both its membrane-localized state and translocation of the Notch intracellular domain into the nucleus upon ligand activation. LIN-12::mNG localized to the nucleus in cells where and when Notch signaling is known to be active and provided a real-time readout of Notch activity in vivo that complements existing biosensors and transcriptional reporters. We also report an allele of endogenous lin-12 that we tagged with both mNG and an auxin-inducible degron, to facilitate conditional LIN-12 protein degradation. This toolkit provides novel reagents for the C. elegans research community to investigate mechanisms of Notch signaling and its functions in vivo .

Using newly optimized genetic tools to probe Strongyloides sensory behaviors

The oft-neglected human-parasitic threadworm, Strongyloides stercoralis, infects roughly eight percent of the global population, placing disproportionate medical and economic burden upon marginalized communities. While current chemotherapies treat strongyloidiasis, disease recrudescence and the looming threat of anthelminthic resistance necessitate novel strategies for nematode control. Throughout its life cycle, S. stercoralis relies upon sensory cues to aid in environmental navigation and coordinate developmental progression. Odorants, tastants, gases, and temperature have been shown to shape parasite behaviors that drive host seeking and infectivity; however, many of these sensory behaviors remain poorly understood, and their underlying molecular and neural mechanisms are largely uncharacterized. Disruption of sensory circuits essential to parasitism presents a promising strategy for future interventions. In this review, we describe our current understanding of sensory behaviors - namely olfactory, gustatory, gas sensing, and thermosensory behaviors - in Strongyloides spp. We also highlight the ever-growing cache of genetic tools optimized for use in Strongyloides that have facilitated these findings, including transgenesis, CRISPR/Cas9-mediated mutagenesis, RNAi, chemogenetic neuronal silencing, and the use of fluorescent biosensors to measure neuronal activity. Bolstered by these tools, we are poised to enter an era of rapid discovery in Strongyloides sensory neurobiology, which has the potential to shape pioneering advances in the prevention and treatment of strongyloidiasis.

Rapid and specific degradation of endogenous proteins in mouse models using auxin-inducible degrons

Auxin-inducible degrons are a chemical genetic tool for targeted protein degradation and are widely used to study protein function in cultured mammalian cells. Here, we develop CRISPR-engineered mouse lines that enable rapid and highly specific degradation of tagged endogenous proteins in vivo. Most but not all cell types are competent for degradation. By combining ligand titrations with genetic crosses to generate animals with different allelic combinations, we show that degradation kinetics depend upon the dose of the tagged protein, ligand, and the E3 ligase substrate receptor TIR1. Rapid degradation of condensin I and II - two essential regulators of mitotic chromosome structure - revealed that both complexes are individually required for cell division in precursor lymphocytes, but not in their differentiated peripheral lymphocyte derivatives. This generalisable approach provides unprecedented temporal control over the dose of endogenous proteins in mouse models, with implications for studying essential biological pathways and modelling drug activity in mammalian tissues.

The Q system for conditional gene expression is leaky and lacks dynamic range in C. elegans neurons

The Q system allows for conditional gene expression in several organisms, including C. elegans . We aimed to apply this system in C. elegans neurons to obtain temporally-resolved, tissue-specific expression of a fluorescent reporter. We report that, in our hands, there is undesired expression of the reporter in conditions where expression is supposed to be repressed. In addition, in this setup, the signal‑to‑noise ratio of the Q system is unfavorable. We conclude that the Q system is far from optimal in the C. elegans nervous system, and advise cautious use.

Genome editing in animals with minimal PAM CRISPR-Cas9 enzymes

The requirement for Cas nucleases to recognize a specific PAM is a major restriction for genome editing. SpCas9 variants SpG and SpRY, recognizing NGN and NRN PAMs, respectively, have contributed to increase the number of editable genomic sites in cell cultures and plants. However, their use has not been demonstrated in animals. Here we study the nuclease activity of SpG and SpRY by targeting 40 sites in zebrafish and C. elegans. Delivered as mRNA-gRNA or ribonucleoprotein (RNP) complexes, SpG and SpRY were able to induce mutations in vivo, albeit at a lower rate than SpCas9 in equivalent formulations. This lower activity was overcome by optimizing mRNA-gRNA or RNP concentration, leading to mutagenesis at regions inaccessible to SpCas9. We also found that the CRISPRscan algorithm could help to predict SpG and SpRY targets with high activity in vivo. Finally, we applied SpG and SpRY to generate knock-ins by homology-directed repair. Altogether, our results expand the CRISPR-Cas targeting genomic landscape in animals.

Inducible degradation of dosage compensation protein DPY-27 facilitates isolation of Caenorhabditis elegans males for molecular and biochemical analyses

Biological sex affects numerous aspects of biology, yet how sex influences different biological processes have not been extensively studied at the molecular level. Caenorhabditis elegans, with both hermaphrodites (functionally females as adults) and males, is an excellent system to uncover how sex influences physiology. Here, we describe a method to isolate large quantities of C. elegans males by conditionally degrading DPY-27, a component of the dosage compensation complex essential for hermaphrodite, but not male, development. We show that germ cells from males isolated following DPY-27 degradation undergo meiosis and spermiogenesis like wild type and these males are competent to mate and sire viable offspring. We further demonstrate the efficacy of this system by analyzing gene expression and performing affinity pull-downs from male worm extracts.

Rapid assessment of the temporal function and phenotypic reversibility of neurodevelopmental disorder risk genes in Caenorhabditis elegans

Recent studies have indicated that some phenotypes caused by decreased function of select neurodevelopmental disorder (NDD) risk genes can be reversed by restoring gene function in adulthood. However, few of the hundreds of risk genes have been assessed for adult phenotypic reversibility. We developed a strategy to rapidly assess the temporal requirements and phenotypic reversibility of NDD risk gene orthologs using a conditional protein degradation system and machine-vision phenotypic profiling in Caenorhabditis elegans. We measured how degrading and re-expressing orthologs of EBF3, BRN3A and DYNC1H1 at multiple periods throughout development affect 30 morphological, locomotor, sensory and learning phenotypes. We found that phenotypic reversibility was possible for each gene studied. However, the temporal requirements of gene function and degree of rescue varied by gene and phenotype. This work highlights the critical need to assess multiple windows of degradation and re-expression and a large number of phenotypes to understand the many roles a gene can have across the lifespan. This work also demonstrates the benefits of using a high-throughput model system to prioritize NDD risk genes for re-expression studies in other organisms.

Summary: We identified diverse temporal functional windows and phenotypic reversibility profiles for three neurodevelopmental disorder risk genes: EBF3•unc-3, BRN3A•unc-86 and DYNC1H1•dhc-1. Re-expression of certain genes could rescue multiple phenotypes later in life, prioritizing them for study.

New Roles for MicroRNAs in Old Worms

The use of Caenorhabditis elegans as a model organism in aging research has been integral to our understanding of genes and pathways involved in this process. Several well-conserved signaling pathways that respond to insulin signaling, diet, and assaults to proteostasis have defined roles in controlling lifespan. New evidence shows that microRNAs (miRNAs) play prominent roles in regulating these pathways. In some cases, key aging-related genes have been established as direct targets of specific miRNAs. However, the precise functions of other miRNAs and their protein cofactors in promoting or antagonizing longevity still need to be determined. Here, we highlight recently uncovered roles of miRNAs in common aging pathways, as well as new techniques for the ongoing discovery of miRNA functions in aging C. elegans.

An engineered, orthogonal auxin analog/AtTIR1(F79G) pairing improves both specificity and efficacy of the auxin degradation system in Caenorhabditis elegans

The auxin-inducible degradation system in C. elegans allows for spatial and temporal control of protein degradation via heterologous expression of a single Arabidopsis thaliana F-box protein, transport inhibitor response 1 (AtTIR1). In this system, exogenous auxin (Indole-3-acetic acid; IAA) enhances the ability of AtTIR1 to function as a substrate recognition component that adapts engineered degron-tagged proteins to the endogenous C. elegans E3 ubiquitin ligases complex [SKR-1/2-CUL-1-F-box (SCF)], targeting them for degradation by the proteosome. While this system has been employed to dissect the developmental functions of many C. elegans proteins, we have found that several auxin-inducible degron (AID)-tagged proteins are constitutively degraded by AtTIR1 in the absence of auxin, leading to undesired loss-of-function phenotypes. In this manuscript, we adapt an orthogonal auxin derivative/mutant AtTIR1 pair [C. elegans AID version 2 (C.e.AIDv2)] that transforms the specificity of allosteric regulation of TIR1 from IAA to one that is dependent on an auxin derivative harboring a bulky aryl group (5-Ph-IAA). We find that a mutant AtTIR1(F79G) allele that alters the ligand-binding interface of TIR1 dramatically reduces ligand-independent degradation of multiple AID*-tagged proteins. In addition to solving the ectopic degradation problem for some AID-targets, the addition of 5-Ph-IAA to culture media of animals expressing AtTIR1(F79G) leads to more penetrant loss-of-function phenotypes for AID*-tagged proteins than those elicited by the AtTIR1-IAA pairing at similar auxin analog concentrations. The improved specificity and efficacy afforded by the mutant AtTIR1(F79G) allele expand the utility of the AID system and broaden the number of proteins that can be effectively targeted with it.

The auxin-inducible degron 2 (AID2) system enables controlled protein knockdown during embryogenesis and development in Caenorhabditis elegans

Targeted protein degradation using the auxin-inducible degron (AID) system is garnering attention in the research field of Caenorhabditis elegans, because of the rapid and efficient target depletion it affords, which can be controlled by treating the animals with the phytohormone auxin. However, the current AID system has drawbacks, i.e., leaky degradation in the absence of auxin and the requirement for high auxin doses. Furthermore, it is challenging to deplete degron-fused proteins in embryos because of their eggshell, which blocks auxin permeability. Here, we apply an improved AID2 system utilizing AtTIR1(F79G) and 5-phenyl-indole-3-acetic acid (5-Ph-IAA) to C. elegans and demonstrated that it confers better degradation control vs the previous system by suppressing leaky degradation and inducing sharp degradation using 1,300-fold lower 5-Ph-IAA doses. We successfully degraded the endogenous histone H2A.Z protein fused to an mAID degron and disclosed its requirement in larval growth and reproduction, regardless of the presence of maternally inherited H2A.Z molecules. Moreover, we developed an eggshell-permeable 5-Ph-IAA analog, 5-Ph-IAA-AM, that affords an enhanced degradation in laid embryos. Our improved system will contribute to the disclosure of the roles of proteins in C. elegans, in particular those that are involved in embryogenesis and development, through temporally controlled protein degradation.

Floxed exon (Flexon): A flexibly positioned stop cassette for recombinase-mediated conditional gene expression

Tools that afford spatiotemporal control of gene expression are crucial for studying genes and processes in multicellular organisms. Stop cassettes consist of exogenous sequences that interrupt gene expression and flanking site-specific recombinase sites to allow for tissue-specific excision and restoration of function by expression of the cognate recombinase. We describe a stop cassette called a flexon, composed of an artificial exon flanked by artificial introns that can be flexibly positioned in a gene. We demonstrate its efficacy in Caenorhabditis elegans for lineage-specific control of gene expression and for tissue-specific RNA interference and discuss other potential uses. The Flexon approach should be feasible in any system amenable to site-specific recombination-based methods and applicable to diverse areas including development, neuroscience, and metabolism.

Conditional gene expression is a powerful tool for genetic analysis of biological phenomena. In the widely used “lox-stop-lox” approach, insertion of a stop cassette consisting of a series of stop codons and polyadenylation signals flanked by lox sites into the 5′ untranslated region (UTR) of a gene prevents expression until the cassette is excised by tissue-specific expression of Cre recombinase. Although lox-stop-lox and similar approaches using other site-specific recombinases have been successfully used in many experimental systems, this design has certain limitations. Here, we describe the Floxed exon (Flexon) approach, which uses a stop cassette composed of an artificial exon flanked by artificial introns, designed to cause premature termination of translation and nonsense-mediated decay of the mRNA and allowing for flexible placement into a gene. We demonstrate its efficacy in Caenorhabditis elegans by showing that, when promoters that cause weak and/or transient cell-specific expression are used to drive Cre in combination with a gfp(flexon) transgene, strong and sustained expression of green fluorescent protein (GFP) is obtained in specific lineages. We also demonstrate its efficacy in an endogenous gene context: we inserted a flexon into the Argonaute gene rde-1 to abrogate RNA interference (RNAi), and restored RNAi tissue specifically by expression of Cre. Finally, we describe several potential additional applications of the Flexon approach, including more precise control of gene expression using intersectional methods, tissue-specific protein degradation, and generation of genetic mosaics. The Flexon approach should be feasible in any system where a site-specific recombination-based method may be applied.

Observing and Quantifying Fluorescent Reporters

Genetically encoded fluorescent reporters take advantage of C. elegans' transparency to allow non-invasive, in vivo observation, and recording of physiological processes in intact animals. Here, we discuss the basic microscope components required to observe, image, and measure fluorescent proteins in live animals for students and researchers who work with C. elegans but have limited experience with fluorescence imaging and analysis.

Imaging Epidermal Cell Rearrangement in the C. elegans Embryo

The Caenorhabditis elegans embryo is well suited for analysis of directed cell rearrangement via modern microscopy, due to its simple organization, short generation time, transparency, invariant lineage, and the ability to generate engineered embryos expressing various fluorescent proteins. This chapter provides an overview of routine microscopy techniques for imaging dorsal intercalation, a convergent extension-like morphogenetic movement in the embryonic epidermis of C. elegans, including making agar mounts, low-cost four-dimensional (4D) Nomarski microscopy, laser microsurgery, and 4D fluorescence microscopy using actin and junctional fusion proteins, as well as tissue-specific promoters useful for studying dorsal intercalation.

A tRNA processing enzyme is a key regulator of the mitochondrial unfolded protein response

The mitochondrial unfolded protein response (UPR^mt) has emerged as a predominant mechanism that preserves mitochondrial function. Consequently, multiple pathways likely exist to modulate UPR^mt. We discovered that the tRNA processing enzyme, homolog of ELAC2 (HOE-1), is key to UPR^mt regulation in Caenorhabditis elegans. We find that nuclear HOE-1 is necessary and sufficient to robustly activate UPR^mt. We show that HOE-1 acts via transcription factors ATFS-1 and DVE-1 that are crucial for UPR^mt. Mechanistically, we show that HOE-1 likely mediates its effects via tRNAs, as blocking tRNA export prevents HOE-1-induced UPR^mt. Interestingly, we find that HOE-1 does not act via the integrated stress response, which can be activated by uncharged tRNAs, pointing toward its reliance on a new mechanism. Finally, we show that the subcellular localization of HOE-1 is responsive to mitochondrial stress and is subject to negative regulation via ATFS-1. Together, we have discovered a novel RNA-based cellular pathway that modulates UPR^mt.

Highly improved cloning efficiency for plasmid-based CRISPR knock-in in C. elegans

Plasmid-based CRISPR knock-in is a streamlined, scalable, and versatile approach for generating fluorescent protein tags in C. elegans (Dickinson et al. 2015; Schwartz and Jorgensen 2016). However, compared to more recent protocols that utilize commercially available Cas9/RNP products and linear DNA repair templates (Dokshin et al. 2018; Ghanta and Mello 2020), the cloning required for plasmid-based protocols has been cited as a drawback of this knock-in approach. Using thorough quantitative assessment, we have found that cloning efficiency can reproducibly reach 90% for the plasmids of the self-excising cassette (SEC) selection method, essentially resolving cloning as a burden for plasmid-based CRISPR knock-in.

Screening by deep sequencing reveals mediators of microRNA tailing in C. elegans

microRNAs are frequently modified by addition of untemplated nucleotides to the 3' end, but the role of this tailing is often unclear. Here we characterize the prevalence and functional consequences of microRNA tailing in vivo, using Caenorhabditis elegans. MicroRNA tailing in C. elegans consists mostly of mono-uridylation of mature microRNA species, with rarer mono-adenylation which is likely added to microRNA precursors. Through a targeted RNAi screen, we discover that the TUT4/TUT7 gene family member CID-1/CDE-1/PUP-1 is required for uridylation, whereas the GLD2 gene family member F31C3.2-here named GLD-2-related 2 (GLDR-2)-is required for adenylation. Thus, the TUT4/TUT7 and GLD2 gene families have broadly conserved roles in miRNA modification. We specifically examine the role of tailing in microRNA turnover. We determine half-lives of microRNAs after acute inactivation of microRNA biogenesis, revealing that half-lives are generally long (median = 20.7 h), as observed in other systems. Although we observe that the proportion of tailed species increases over time after biogenesis, disrupting tailing does not alter microRNA decay. Thus, tailing is not a global regulator of decay in C. elegans. Nonetheless, by identifying the responsible enzymes, this study lays the groundwork to explore whether tailing plays more specialized context- or miRNA-specific regulatory roles.

Deletion of a putative HDA-1 binding site in the hlh-2 promoter eliminates expression in C. elegans dorsal uterine cells

The helix-loop-helix transcription factor hlh-2 (E/Daughterless) has been shown to play an important role in regulating cell fate patterning, cell cycle, and basement membrane invasion in the context of the development of the C. elegans somatic gonad. Here, using CRISPR/Cas9 genome engineering, we generated a new hlh-2 allele (hlh-2(Δ-1303-702)) in the endogenous, GFP-tagged hlh-2 locus. This allele represents a deletion of a 601 bp region in the hlh-2 promoter that contains a putative binding site of the histone deacetylase hda-1 (HDAC) according to publicly available ChIP-sequencing data. Strikingly, we find that HLH-2 expression is virtually absent in the dorsal uterine cells of hlh-2(Δ-1303-702) animals compared to wild type controls. Levels of HLH-2 in the anchor cell and ventral uterine cells are only modestly reduced in the mutant; however, this does not seem to be functionally significant based on the lack of relevant phenotypes and expression levels of a downstream gene, NHR-67 (TLX/Tailless/NR2E1), in these cells. Taken together, these results support growing evidence that HDACs can potentially positively regulate transcription and provide a new reagent for studying hlh-2 regulation.

Conditional immobilization for live imaging Caenorhabditis elegans using auxin-dependent protein depletion

The visualization of biological processes using fluorescent proteins and dyes in living organisms has enabled numerous scientific discoveries. The nematode Caenorhabditis elegans is a widely used model organism for live imaging studies since the transparent nature of the worm enables imaging of nearly all tissues within a whole, intact animal. While current techniques are optimized to enable the immobilization of hermaphrodite worms for live imaging, many of these approaches fail to successfully restrain the smaller male worms. To enable live imaging of worms of both sexes, we developed a new genetic, conditional immobilization tool that uses the auxin-inducible degron (AID) system to immobilize both adult and larval hermaphrodite and male worms for live imaging. Based on chromosome location, mutant phenotype, and predicted germline consequence, we identified and AID-tagged three candidate genes (unc-18, unc-104, and unc-52). Strains with these AID-tagged genes were placed on auxin and tested for mobility and germline defects. Among the candidate genes, auxin-mediated depletion of UNC-18 caused significant immobilization of both hermaphrodite and male worms that was also partially reversible upon removal from auxin. Notably, we found that male worms require a higher concentration of auxin for a similar amount of immobilization as hermaphrodites, thereby suggesting a potential sex-specific difference in auxin absorption and/or processing. In both males and hermaphrodites, depletion of UNC-18 did not largely alter fertility, germline progression, nor meiotic recombination. Finally, we demonstrate that this new genetic tool can successfully immobilize both sexes enabling live imaging studies of sexually dimorphic features in C. elegans.

Efficient generation of a single-copy eft-3p::TIR1::F2A:: BFP::AID*::NLS allele in the C. elegans ttTi5605 insertion site through recombination-mediated cassette exchange

The auxin-inducible degron (AID) system is a widely used system to conditionally deplete proteins. Using CRISPR/Cas9-based genome editing in C. elegans, we recently generated a set of single-copy, tissue-specific and pan-somatic TIR1-expressing strains carrying a BFP reporter inserted in single-copy into two commonly used, well-characterized genetic loci. However, we were unable to obtain a strain carrying a pan-somatic eft-3p::TIR1::F2A::BFP::AID*::NLS transgene inserted into the chromosome II ttTi5605 insertion site. Using recombination-mediated cassette exchange (RMCE) we were able to efficiently obtain this knock-in. The resulting strain displayed equivalent depletion of an AID*::GFP reporter compared to our previously generated eft-3p::TIR1::F2A::BFP::AID*::NLS transgene knocked into the chromosome I ttTi4348 insertion site. This work highlights the power of RMCE for generating new reagents for the AID system and provides an eft-3p::TIR1::F2A::BFP::AID*::NLS allele on chromosome II which will simplify genetic crossing schemes when using the AID system.

Antagonistic fungal enterotoxins intersect at multiple levels with host innate immune defences

Animals and plants need to defend themselves from pathogen attack. Their defences drive innovation in virulence mechanisms, leading to never-ending cycles of co-evolution in both hosts and pathogens. A full understanding of host immunity therefore requires examination of pathogen virulence strategies. Here, we take advantage of the well-studied innate immune system of Caenorhabditis elegans to dissect the action of two virulence factors from its natural fungal pathogen Drechmeria coniospora. We show that these two enterotoxins have strikingly different effects when expressed individually in the nematode epidermis. One is able to interfere with diverse aspects of host cell biology, altering vesicle trafficking and preventing the key STAT-like transcription factor STA-2 from activating defensive antimicrobial peptide gene expression. The second increases STA-2 levels in the nucleus, modifies the nucleolus, and, potentially as a consequence of a host surveillance mechanism, causes increased defence gene expression. Our results highlight the remarkably complex and potentially antagonistic mechanisms that come into play in the interaction between co-evolved hosts and pathogens.

Auxin treatment increases lifespan in Caenorhabditis elegans

The auxin-inducible degradation system (AID) has proven to be a highly versatile technology for rapid, robust and reversible depletion of proteins in multiple model systems. In recent years, AID has been adapted into the nematode Caenorhabditis elegans as a tool for conditional protein knockdown. Numerous transgenic strains have been created that, upon auxin exposure, undergo protein inactivation in the worm germline or somatic tissues, both during development and in young adults. Since longevity assays often involve long-term gene- and protein-manipulation, the facility for spatiotemporally precise and extended protein removal makes AID a potentially highly valuable tool for aging biology. However, whether auxins themselves impact worm longevity has not been directly addressed. Here, we show that prolonged exposure to indole 3-acetic acid (IAA), the auxin used in worm AID studies, extends lifespan. We also report that two transgenic strains expressing Arabidopsis proteins that are key components of the AID platform are longer lived than wild-type animals. Together, our results highlight the necessity for exercising caution while utilizing AID for longevity studies and in interpreting the resulting data.

This article has an associated First Person interview with the first author of the paper.

Summary: We report that auxin and auxin-inducible protein degradation tools alter lifespan in C. elegans.