Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2003
Publication Date: 4/1/2004
Citation: Vaghchhipawala, Z.E., Schlueter, J.A., Shoemaker, R.C., Mackenzie, S.A. 2004. Characterization of soybean fgam synthase genes and their expression within nematode feeding sites. Genome. v. 47. p. 404-413. Interpretive Summary: Infestations of the soybean cyst nematode results in many millions of dollars lost to soybean production throughout the United States. Understanding the processes by which a plant responds to nematode attack will aid in creation of resistant soybeans. In this paper the authors report the identification of soybean hereditary material that responds to nematode attack. One gene was placed on the genetic roadmap and was shown to reside close to a region predicted to contain a resistance gene. The authors further showed that at least two copies of the gene exist, and that they respond to nematode attack differently. Examination of how the genes respond suggested that plant gene expression is redirected within the site of nematode attack to benefit the parasite. This information will be useful to scientists in developing models for creating better nematode resistance in soybeans.
Technical Abstract: A system to identify genes with modified expression in response to soybean cyst nematode infection led to the previous identification, by reverse transcription-polymerase chain reaction, of several genes within the nematode feeding sites. The genes were mapped to reveal their linkage relationship to known QTLs associated with soybean cyst nematode (SCN) resistance. One candidate, a phosphoribosylformylglycinamidine (FGAM) synthase gene, mapped to the same genomic interval as the major SCN resistance gene Rhg1 within Linkage Group G. Cloning of this gene from a bacterial artificial chromosome (BAC) library revealed two highly homologous copies. The gene appeared to be well conserved from bacteria to humans. Promoter analysis of the two soybean homologs was carried out with the Arabidopsis thaliana-Heterodera schachtii system to investigate gene response to nematode feeding. The two promoters and their derived deletion constructions effected green fluorescent protein expression within nematode feeding sites. The 1.0-kb promoter sequence immediately adjacent to the translation start site was sufficient to direct expression of GFP within syncytia. A wound-inducible element and a floral organ-specific expression sequence were also identified within these promoters. Although a nematode responsive element could not be identified, the observed expression of GFP within feeding sites supports the hypothesis that plant gene expression is redirected within feeding sites to benefit the parasite.