Gene expression in feeding sites during soybean-soybean cyst nematode interaction: Characterization of phosphoribosylformylglycinamidine synthase gene
Abstract
Soybean is one of the most economically important crops in the United States and the soybean cyst nematode is its most destructive pest causing heavy yield loss. These obligate parasites share a unique source-sink relationship with their host and induce a reorganization of root cells to establish a feeding site called the syncytium. This study was initiated in a simplified genetic system to identify genes with modified expression in response to nematode infection. Reverse transcription-Polymerase chain reaction assay was used to confirm the inducible nature of identified genes in the nematode feeding sites. These genes were mapped to reveal their relationship to known soybean cyst nematode (SCN) resistance loci. One candidate “FGAM synthase” maps to the same interval as the major SCN resistance gene on top of Linkage Group G. Cloning of this gene from a bacterial artificial chromosome (BAC) library reveals two highly homologous copies of this gene, not surprising considering the degree of duplications within the soybean genome. This gene was also found to be highly conserved throughout evolution from bacteria to human beings. Promoter analysis of these two genes was carried out in a heterologous system of A. thaliana. The two promoters and their deletion constructs were shown to drive green fluorescent protein expression within feeding sites. A 1.0 kb promoter fragment was found to be sufficient to drive expression of GFP within syncytia. Even though a nematode responsive element could not be detected readily within the promoters, the expression of GFP at feeding sites suggests that a nematode has been able to utilize existing plant sequences to redirect plant gene expression within feeding sites for its own benefit.
Degree
Ph.D.
Advisors
Nielsen, Purdue University.
Subject Area
Agronomy|Plant propagation|Plant pathology
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