Investigating the role of neuropeptides in plant parasitic nematodes
Plant parasitic nematodes (PPNs) devastate agriculture on a global scale causing severe annual economic losses. Withdrawal of the chemical nematicides used to control PPNs, due to their harmful environmental effects, has led to a short fall in our ability to manage these pests. This thesis explores different methodologies available to probe neuropeptide gene function in economically important PPNs. A proof of concept study utilising transgenic Bacillus subtilis to deliver PPN neuropeptides in a tomato seedling invasion assay identified several neuropeptides which induce aberrant behaviours in Meloidogyne incognita and Globodera pallida conferring resistance to tomato seedlings. This thesis demonstrated Bacillus subtilis signal peptide optimisation using NLP-15b. NLP-15b showed a potent effect during initial studies conferring host resistance from Meloidogyne incognita and Globodera pallida invasion. The nlp-15 gene was chosen for further investigations using several available platforms. Firstly, localisation of nlp-15 in Radopholus similis and to cells of the anterior nervous system suggested its involvement in sensory perception. Various RNA interference (RNAi) protocols were developed to induce silencing of nlp-15. Additionally, a Virus Induced Gene Silencing (VIGS) method was used to try and silence nlp-15 in invading Meloidogyne incognita nematodes. Taken together, the data highlight a need to further understand gene silencing techniques with respect to neuronal targets so we can develop methods that promote further study of these genes. Finally, a protocol was developed to produce transgenic tomato plants synthesising an RNAi silencing construct to target nlp-15 in feeding nematodes.
Networked Digital Library of Theses and Dissertations