Cyst nematodes in the genus Heterodera are sedentary endoparasites that induce elaborate feeding cells within host roots by secreting proteins produced within nematode esophageal glands into plant cells. Functional analyses of selected cyst nematode parasitism genes that encode such secreted proteins was the objective of this dissertation. Homologs of four parasitism genes initially isolated from Heterodera glycines, including Hg4F01 (annexin-like protein), HgSYV46 (CLAVATA3-like plant peptide mimic), Hg4E02 and Hg5D08 (novel proteins with putative host nuclear localization) were isolated from Heterodera schachtii, which can infect Arabidopsis thaliana. Greater than 90% nucleotide and predicted amino acid identity existed between the four parasitism genes homologs of H. glycines and H. schachtii. mRNA in situ hybridization and immunolocalization confirmed the expression of each gene product exclusively within the nematode esophageal gland cells. Since eukaryotic annexins affect many cellular processes involving calcium-dependent membrane association, the potential function of the Hs4F01 secreted into plant cells was analyzed. Similar to annexin mutants in Arabidopsis, transgenic Arabidopsis expressing Hs4F01 produced no observable plant phenotype, but were more susceptible to nematode infection. Hypersensitivity to osmotic stress in an Arabidopsis annAt1 annexin mutant was reduced (complemented) in mutants that expressed Hs4F01, suggesting a functional similarity of nematode and plant annexins within plant cells. Host derived RNA interference (RNAi) to silence Hs4F01 transcripts significantly reduced the number of H. schachtii females developing on roots that express dsRNA to Hs4F01. Expression of Hs4E02 and Hs5D08 in Arabidopsis produced no observable plant phenotype and susceptibility to H. schachtii was not altered in plants that expressed Hs4E02. Silencing of HsSYV46 using host-derived RNAi demonstrated a significant reduction in the development of nematode females on Arabidopsis roots that expressed double-stranded RNA to HsSYV46. Expression of dsRNA to Hs4E02 and Hs5D08 in Arabidopsis roots did not affect nematode susceptibility. In summary, parasitism gene products confirmed to have cellular functions similar to their plant homologs, including Hs4F01 (annexin-like protein) and HsSYV46 (CLAVATA/ESR-like peptide) were demonstrated by RNAi to have a significant biological role in cyst nematode parasitism of host plant roots.
| Identifer | oai:union.ndltd.org:NCSU/oai:NCSU:etd-03102008-221413 |
| Date | 16 April 2008 |
| Creators | Patel, Nrupali |
| Contributors | Dr Marc Cubeta, Dr Prema Arasu, Dr William Thompson, Dr. Eric Davis |
| Publisher | NCSU |
| Source Sets | North Carolina State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://www.lib.ncsu.edu/theses/available/etd-03102008-221413/ |
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