In this paper we prove instances of the cyclic sieving phenomenon for finite Grassmannians and partial flag varieties, which carry the action of various tori in the finite general linear group GL_n(F_q). The polynomials involved are sums of certain weights of the minimal length parabolic coset representatives of the symmetric group S_n, where the weight of a coset representative can be written as a product over its inversions.

Work in yeast models has benefitted tremendously from the insertion of epitope or fluorescence tags at the native gene locus to study protein function and behavior under physiological conditions. In contrast, work in mammalian cells largely relies on overexpression of tagged proteins because high-quality antibodies are only available for a fraction of the mammalian proteome. CRISPR/Cas9-mediated genome editing has recently emerged as a powerful genome-modifying tool that can also be exploited to insert various tags and fluorophores at gene loci to study the physiological behavior of proteins in most organisms, including mammals. Here we describe a versatile toolset for rapid tagging of endogenous proteins. The strategy utilizes CRISPR/Cas9 and microhomology-mediated end joining repair for efficient tagging. We provide tools to insert 3×HA, His₆FLAG, His₆-Biotin-TEV-RGSHis₆, mCherry, GFP, and the auxin-inducible degron tag for compound-induced protein depletion. This approach and the developed tools should greatly facilitate functional analysis of proteins in their native environment.

Neuromodulators influence the activities of collections of neurons and have profound impacts on animal behavior. Male courtship drive is complex and subject to neuromodulatory control. Using the fruit fly Drosophila melanogaster, we identified neurons in the brain (inferior posterior slope; IPS) that impact courtship drive and were controlled by tyramine-a biogenic amine related to dopamine, whose roles in most animals are enigmatic. We knocked out a tyramine-specific receptor, TyrR, which was expressed in IPS neurons. Loss of TyrR led to a striking elevation in courtship activity between males. This effect occurred only in the absence of females, as TyrR(Gal4) mutant males exhibited a wild-type preference for females. Artificial hyperactivation of IPS neurons caused a large increase in male-male courtship, whereas suppression of IPS activity decreased male-female courtship. We conclude that TyrR is a receptor for tyramine, and suggest that it serves to curb high levels of courtship activity through functioning as an inhibitory neuromodulator.

The molecular mechanisms of coevolution between plants and insects remain elusive. GABA receptors are targets of many neurotoxic terpenoids, which represent the most diverse array of natural products known. Over deep evolutionary time, as plant terpene synthases diversified in plants, so did plant terpenoid defence repertoires. Here we show that herbivorous insects and their predators evolved convergent amino acid changing substitutions in duplicated copies of the Resistance to dieldrin (Rdl) gene that encodes the GABA receptor, and that the evolution of duplicated Rdl and terpenoid-resistant GABA receptors is associated with the diversification of moths and butterflies. These same substitutions also evolved in pests exposed to synthetic insecticides that target the GABA receptor. We used in vivo genome editing in Drosophila melanogaster to evaluate the fitness effects of each putative resistance mutation and found that pleiotropy both facilitates and constrains the evolution of GABA receptor resistance. The same genetic changes that confer resistance to terpenoids across 300 Myr of insect evolution have re-evolved in response to synthetic analogues over one human lifespan.

Neuromodulators influence the activities of collections of neurons and have profound impacts on animal behavior. Male courtship drive is complex and subject to neuromodulatory control. Using the fruit fly Drosophila melanogaster, we identified neurons in the brain (inferior posterior slope; IPS) that impact courtship drive and were controlled by tyramine-a biogenic amine related to dopamine, whose roles in most animals are enigmatic. We knocked out a tyramine-specific receptor, TyrR, which was expressed in IPS neurons. Loss of TyrR led to a striking elevation in courtship activity between males. This effect occurred only in the absence of females, as TyrR(Gal4) mutant males exhibited a wild-type preference for females. Artificial hyperactivation of IPS neurons caused a large increase in male-male courtship, whereas suppression of IPS activity decreased male-female courtship. We conclude that TyrR is a receptor for tyramine, and suggest that it serves to curb high levels of courtship activity through functioning as an inhibitory neuromodulator.

The Varroa destructor mite is a devastating parasite of Apis mellifera honeybees. They can cause colonies to collapse by spreading viruses and feeding on the fat reserves of adults and larvae. Amitraz is used to control mites due to its low toxicity to bees; however, the mechanism of bee resistance to amitraz remains unknown. In this study, we found that amitraz and its major metabolite potently activated all four mite octopamine receptors. Behavioral assays using Drosophila null mutants of octopamine receptors identified one receptor subtype Octβ2R as the sole target of amitraz in vivo. We found that thermogenetic activation of octβ2R-expressing neurons mimics amitraz poisoning symptoms in target pests. We next confirmed that the mite Octβ2R was more sensitive to amitraz and its metabolite than the bee Octβ2R in pharmacological assays and transgenic flies. Furthermore, replacement of three bee-specific residues with the counterparts in the mite receptor increased amitraz sensitivity of the bee Octβ2R, indicating that the relative insensitivity of their receptor is the major mechanism for honeybees to resist amitraz. The present findings have important implications for resistance management and the design of safer insecticides that selectively target pests while maintaining low toxicity to non-target pollinators.

Pheromones are used for conspecific communication by many animals. In Drosophila, the volatile male-specific pheromone 11-cis vaccenyl acetate (cVA) supplies an important signal for gender recognition. Sensing of cVA by the olfactory system depends on multiple components, including an olfactory receptor (OR67d), the co-receptor ORCO, and an odorant binding protein (LUSH). In addition, a CD36 related protein, sensory neuron membrane protein 1 (SNMP1) is also involved in cVA detection. Loss of SNMP1 has been reported to eliminate cVA responsiveness, and to greatly increase spontaneous activity of OR67d-expressing olfactory receptor neurons (ORNs). Here, we found the snmp1(1) mutation did not abolish cVA responsiveness or cause high spontaneous activity. The cVA responses in snmp1 mutants displayed a delayed onset, and took longer to reach peak activity than wild-type. Most strikingly, loss of SNMP1 caused a dramatic delay in signal termination. The profound impairment in signal inactivation accounted for the previously reported "spontaneous activity," which represented continuous activation following transient exposure to environmental cVA. We introduced the silk moth receptor (BmOR1) in OR67d ORNs of snmp1(1) flies and found that the ORNs showed slow activation and deactivation kinetics in response to the BmOR1 ligand (bombykol). We expressed the bombykol receptor complex in Xenopus oocytes in the presence or absence of the silk moth SNMP1 (BmSNMP) and found that addition of BmSNMP accelerated receptor activation and deactivation. Our results thus clarify SNMP1 as an important player required for the rapid kinetics of the pheromone response in insects.

Hundreds of neurotoxic insecticides are currently in use. However, only a few direct targets have been identified. Here, using Drosophila and the insecticide flonicamid, we identified nicotinamidase (Naam) as a previous unidentified molecular target for an insecticide. Naam is expressed in chordotonal stretch-receptor neurons, and inhibition of Naam by a metabolite of flonicamid, TFNA-AM (4-trifluoromethylnicotinamide), induces accumulation of substrate nicotinamide and greatly inhibits negative geotaxis. Engineered flies harboring a point mutation in the active site show insecticide resistance and defects in gravity sensing. Bees are resistant to flonicamid because of a gene duplication, resulting in the generation of a TFNA-AM-insensitive Naam. Our results, in combination with the absence of genes encoding Naam in vertebrate genomes, suggest that TFNA-AM and potential species-specific Naam inhibitors could be developed as novel insecticides, anthelmintics, and antimicrobials for agriculture and human health.

Male courtship is provoked by perception of a potential mate. In addition, the likelihood and intensity of courtship are influenced by recent mating experience, which affects sexual drive. Using Drosophila melanogaster, we found that the homolog of mammalian neuropeptide Y, neuropeptide F (NPF), and a cluster of male-specific NPF (NPFM) neurons, regulate courtship through affecting courtship drive. Disrupting NPF signaling produces sexually hyperactive males, which are resistant to sexual satiation, and whose courtship is triggered by sub-optimal stimuli. We found that NPFM neurons make synaptic connections with P1 neurons, which comprise the courtship decision center. Activation of P1 neurons elevates NPFM neuronal activity, which then act through NPF receptor neurons to suppress male courtship, and maintain the proper level of male courtship drive.