Submitted to: Journal of Experimental Botany
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/11/2007
Publication Date: 9/20/2007
Citation: Tucker, M.L., Ehrenfried, M.L., Thai, V., Burke, A. 2007. Soybean cell wall hydrolase gene expression during cyst nematode infection, hypocotyls induced to form roots, leaf abscission, flowers, apical buds, root tips and leaves. Journal of Experimental Botany. 58:3395-3406. Interpretive Summary: Soybean cyst nematode (SCN) is the most economically damaging pathogen of soybean. It has been estimated that damage to the United States soybean crop by SCN costs farmers one billion dollars annually. In order for SCN to colonize the plant root it must form a complex feeding structure inside the root. Part of this process requires the degradation of the plant cell walls. We have identified several genes in soybean that are responsible for cell wall degradation and demonstrated that several of these genes are turned on during nematode infection. The nematode somehow co-opts the plant into making the enzymes that degrade the soybean cell walls. A better understanding of how these genes are regulated by the nematode will greatly improve the ability of scientists and industrial partners to control SCN infection of soybean.
Technical Abstract: Degenerate primers were prepared to conserved motifs in plant cellulases (endo-1,4-glucanases), polygalacturonases (PGs) and xyloglucan endotransglycosylases (XETs). PCR products were identified for multiple soybean cell wall hydrolases expressed in soybean cyst nematode (SCN) infected roots. Gene-specific primers were prepared for all of these PCR products in addition to a few more sequences in the GenBank nr database and several contigs created from the GenBank soybean ESTs. In all, RT-PCR was completed on12 cellulases, 15 PGs and 4 XETs. All but one cellulase and two XETs produced a PCR product using RNA from roots of 14 day-old soybean plants infected with SCN. In addition to standard RT-PCR to confirm that a single product was produced from root RNA, real-time RT-PCR was completed using RNA from soybean roots inoculated with soybean cyst nematodes (SCN), hypocotyls induced to root by treatment with IBA and ethylene, root tips, leaf abscission zones, flowers, apical buds, and expanding leaves. Our primary interest here is the up-regulated expression of multiple hydrolases associated with nematode infected roots and their expression in other plant tissues and developmental processes. Cell wall hydrolase gene expression in SCN infected root tissue was most similar to gene expression in hypocotyls induced to form roots with IBA and ethylene treatment. However, cell wall hydrolase gene expression common to SCN infected root pieces was not elevated in root tips, apical buds, flowers and leaves. Nevertheless, several cell wall hydrolases expressed in SCN infected root pieces were also up-regulated in abscising leaf abscission zones.