The plant-parasitic nematode Meloid?gyne incognita stimulates the de-differentiation of plant root cells into enlarged, multinucleate giant cells which function as transfer cells. Changes in host plant gene expression occur in response to this parasitism and these were monitored in mature feeding site structures (galls) ofM incognita fo~ed in Arabidopsis thaliana. Whole genome microarrays were hybridised with cDNA obtained from galls and from sections ofuninfected root sampled at 21 days post infection. 959 Arabidopsis genes were found to be significantly differentially expressed, of which approximately two thirds were down-regulated.. Microarray data was validated by qRT-PCR analysis of 16 genes representative of a range of microarray fold changes and a Pearson correlation coefficient of 0.78 was obtained. . . Four genes determined as differentially expressed by microarray analysis were selected for promoter::GUS reporter analysis. All constructs 'had some expression in uninfected roots. Transgenic Arabidopsis plants were infected with M incognita or the cyst nematode Heterodera schachtii. The promoter of ammonium transporter gene AtAMT1;2 was consistently repressed in roots associated with both nematode species at all developmental stages observed. GUS expression driven'by the LATERAL ORGANBOUNDARYDOMAIN GENE 41 promoter was induced strongly in galls of fusiform and saccate M incognita but the response to H. schachtii parasitism was not consistent. Promoters for actin depolymerising factor gene ADF3 and a lipid transfer protein/seed storage protein/protease inhibitor gene LTP both showed induction of GUS expression in the galls of fusiform and saccateM incognita. This appeared to be associated with the vasculature for LTP. H. schachtii parasitism at saccate and mature male stages did not alter expression of GUS. Several Solanum lycopersicum (tomato) genes possessing homology to genes differentially regulated in galls induced in Arabidopsis were identified. Expression of these homologs was determined by RT-PCR in feeding sites' structures of M. incognita, Nacobbus aberrans or Globodera pallida. Distinct patterns of expression were observed for the different types of feeding site structure.. Regulation of the homologs was monitored in M incognita galls at three developmental stages and revealed temporal variations in detected expression. Comparison of sets of Arabidopsis genes identified as highly induced or repressed in mature M incognita galls with other biotic stresses revealed that many of these genes were also differentially regulated by Agrobacterium tumefaciens. This suggests that many transcriptional modifications in both systems may be secondary effects rather than primary, causative events.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:486328 |
| Date | January 2007 |
| Creators | Fuller, Victoria |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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