Date of Award
Winter 2025
Project Type
Dissertation
Program or Major
Biochemistry
Degree Name
Doctor of Philosophy
First Advisor
Rick R.H.C Cote
Second Advisor
Kelley K.T Thomas
Third Advisor
David D.P.P Plachetzki
Abstract
There are nearly 4,100 species of plant-parasitic nematodes that pose a serious threat toglobal food security, and it is estimated that about $100 billion of crops are damaged annually due to these plant parasitic nematodes. Also, animal-parasitic nematodes pose a major global health challenge, impacting approximately 3.5 billion individuals annually, particularly in tropical and developing areas. PDEs are significant determinants of cellular levels of cyclic nucleotides because the process of lowering active intracellular cyclic nucleotide second messengers (cAMP and cGMP) in cells is mediated through PDEs. Nematode behavior and lifecycle depend on cyclic nucleotide signaling. However, at present, there is limited knowledge of the physiological role that the individual PDEs play in mediating C. elegans signaling pathways. Mammals possess 11 PDE families (PDE1-PDE11), and nematodes have orthologous PDE genes to six of these families. To evaluate whether the disruption of one or more PDEs will disrupt nematode behavior, we employed several approaches: 1) exposure of wild-type C. elegans to family-specific inhibitors designed to target human PDEs; 2) use of RNA interference (RNAi) to disrupt C. elegans PDEs in vivo; 3) and creation of transgenic strains of C. elegans in which each of the six individual PDE genes was ablated using CRISPR/Cas9 as well as several double “knockout” strains created by genetic crosses. Interestingly, none of the single knockout strains showed major defects in development or reproductive success. The pde-1-/- knockout strain C. elegans was defective in chemotaxis, and exposure of wild-type C. elegans to human PDE1 inhibitors display a similar phenotype. The genetic cross generating pde-2-/-:pde-3-/- double homozygotes failed to produce progeny. Targeting multiple PDEs by treating knockout strains with RNAi or PDE inhibitors resulted in decreased viability and fecundity in specific instances: the pde-1-/-:pde-4-/- strain exposed to pde-3-/- RNAi and the pde-1-/:pde-3-/- strain exposed to pde-4-/- RNAi both showed a significant reduction in fecundity, developmental delays, and lethargic locomotion. Of the six knockout strains, the pde-4-/- strain showed modest hyperactivity compared to wild-type. In addition to this, two human family-specific PDE inhibitors, ITI-214 (PDE1) and MP10 (PDE10), exposed to wild-type C. elegans were lethal at high concentrations whereas the pde-1-/- and pde-5-/- knockout strains were viable, indicating an off-target effect of these compounds. Our results demonstrate that many physiological and behavioural processes observed in C. elegans rely on multiple PDE family members to regulate cyclic nucleotide signalling pathways. Therefore, PDEs represent a promising target for developing chemical or genetic controls to disrupt the lifecycle of parasitic nematodes that infect plant or animal hosts in order to improve agricultural productivity and animal and human health.
Recommended Citation
Galande, Kranti, "PHOSPHODIESTERASES (PDEs) AS POTENTIAL TARGETS FOR DISRUPTING THE LIFE CYCLE OF NEMATODES USING MOLECULAR AND CHEMICAL AGENTS" (2025). Doctoral Dissertations. 2975.
https://scholars.unh.edu/dissertation/2975