W.K. So et al. (2006) European Worm Meeting "Sex pheromone production in dioecious nematodes and the perception pathway delineated by genetics"

W.S. Yeung, M.Y. Wu, C.M. Chan, W.K. So, K.L. Chow

[European Worm Meeting, 2006]

W.K. So, C.M. Chan, M.Y. Wu, W.S. Yeung and K.L. Chow. In dioecious nematodes, finding the mating partner and successful mating is instrumental to their reproductive success. To ensure these tasks are accomplished, sex pheromone production is a common strategy adopted in the nematode world. In Caenorhabditis remanei, a dioecious species, a sex-specific attractant was identified to be produced by females for attracting males. In this study, we focus on four areas of characterization, the properties of the pheromone, its regulatory production in female, male perception and species specification. In the characterization part, our GC-MS analysis result identifies two candidate chemicals in the samples, the exact identity of which will be confirmed by chemical synthesis coupled with bioassays. These attractant substances are produced under tight developmental control in the gonad as confirmed by laser ablation of gonadal progenitor cells in different combination. Their activity could be abolished by mating with males. Based on our pervious results, the males of the androdioecious can be attracted by this sex pheromone. So for the male perception part, we employed males from various Caenorhabditis elegans mutants with defects in cell lineage or molecular function to delineate the perception pathway. Our results show that two different sensory neurons and an interneuron are required. Moreover, a signaling process dependent of G protein coupled receptor is crucial for the pheromone perception, where modulation by other molecular components has been observed. Hypothesis suggesting a conservation of the pheromone perception pathway across different species will be tested using chemo-attraction assay on con-specific and hetero-specific combination of testing animals. (The project is funded by Research Grant Council, Hong Kong.)

Frederick A Partridge et al. (2005) International Worm Meeting "bus-8/nic-1, a glycosyltransferase required for embryogenesis and normal cuticle formation"

Jonathan Hodgkin, Maria J Gravato-Nobre, Frederick A Partridge, Adam W Tearle, William R Schafer

[International Worm Meeting, 2005]

Attachment of pathogens to a host surface is a critical step in infection. We are seeking to understand this process using a Caenorhabditis elegans bacterial infection model. Microbacterium nematophilum adheres to the rectum and post-anal cuticle of the worm. The worm responds by inducing a protective swelling of the underlying tissues (deformed anal region, Dar) [1]. Mutations in the gene bus-8/nic-1 were independently isolated in screens for resistance to infection by M. nematophilum (M.G-N., J.H.), and for nicotine hypersensitivity (W.S.). Weak loss of function mutants complete embryogenesis but produce an abnormal cuticle, preventing bacterial adherence and increasing the permeability of the cuticle to a wide range of drugs; are uncoordinated; and often arrest as larvae. We have examined the structure of the cuticle and the underlying hypodermis by electron microscopy, and see several abnormalities. A bus-8/nic-1 reporter construct is expressed in the seam cells, which supports the role of bus-8/nic-1 in cuticle production. Strong loss of function or null mutants of bus-8/nic-1 arrest as embryos at the two-fold stage, with defects during elongation. In contrast, the typical embryonic phenotype of a disrupted cuticle is normal elongation followed by retraction. This suggests that bus-8/nic-1 has a cuticle-independent role in embryogenesis. We have cloned bus-8/nic-1 and shown that it encodes a putative glycosyltransferase, specific to nematodes, but conserved across the phylum. We will describe our progress in relating the molecular identity of the gene to its role in development.[1] Nicholas, H.R. and Hodgkin, J. (2004) Current Biology 14 1256-61

Narayan, Anusha et al. (2009) International Worm Meeting "Transfer at a thermosensory synapse in C. elegans."

Laurent, Gilles, Sternberg, Paul, Narayan, Anusha

[International Worm Meeting, 2009]

C.elegans is an attractive system for neural circuit analysis. To analyze the functional dynamics of circuits that control behavior, it is necessary to understand the underlying synaptic transformations. Thermotaxis is an established behavior in C. elegans[1-2]. We attempt to characterize the transfer function at a prominent synapse within the thermotactic circuit: between AFD, the primary thermosensory neuron[3], and AIY, its principal post-synaptic partner. We drive expression of Channelrhodopsin-2(chR2), a light-activated cation channel [4], solely in AFD, using a cell-specific promoter, and use whole-cell patch-clamp recording techniques to measure the light-evoked synaptic response at AIY. We are able to reliably activate the presynaptic cell AFD, evoking depolarizing potentials of up to 40 mV and inward currents of up to 15 pA. The postsynaptic response at AIY is small: less than 5 mV, with inward currents of less than 1 pA, and is graded and tonic, lasting the duration of the stimulus. The response reverses around 0 mV and seems to be frequency independent, showing no obvious short-term facilitation or depression. Our results further validate the use of chR2 to stimulate neural activity, and indicate that this synapse has low gain, and transmits information from AFD to AIY with short latencies and high fidelity. It will be interesting to see how AIY integrates this information with other incoming streams, and to examine processing downstream in the thermotactic circuit. 1.Mori, I., H. Sasakura, and A. Kuhara, Worm thermotaxis: a model system for analyzing thermosensation and neural plasticity. Curr Opin Neurobiol, 2007. 17(6): p. 712-9. 2.Ryu, W.S. and A.D. Samuel, Thermotaxis in Caenorhabditis elegans analyzed by measuring responses to defined Thermal stimuli. J Neurosci, 2002. 22(13): p. 5727-33. 3.Clark, D.A., et al., The AFD sensory neurons encode multiple functions underlying thermotactic behavior in Caenorhabditis elegans. J Neurosci, 2006. 26(28): p. 7444-51. 4.Boyden, E.S., et al., Millisecond-timescale, genetically targeted optical control of neural activity. Nat Neurosci, 2005. 8(9): p. 1263-8.