Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/28/2014
Publication Date: 4/16/2014
Citation: Matthews, B.F., Beard, H.S., Brewer, E.P., Kabir, S., Macdonald, M.H., Youssef, R.M. 2014. Ectopic expression of Arabidopsis genes encoding salicylic acid- and jasmonic acid-related proteins confers partial resistance to soybean cyst nematode (Heterodera glycines) in transgenic soybean roots. Biomed Central (BMC) Plant Biology. 14:96. Interpretive Summary: Soybean is a major crop in the US. The soybean cyst nematode (SCN) is the major pathogen of soybean in the US and causes an estimated one billion dollars in damage each year. We selected 31 genes from the model plant, Arabidopsis, that are involved in plant defense against pathogens. The genes were individually inserted into soybean roots to make transgenic roots that over expressed the gene. The transgenic roots were inoculated with SCN, and the effect of over expression of each gene was determined by counting the number of cysts formed by the nematodes on the roots after 35 days. Three Arabidopsis genes reduced the number of SCN females 60% or more as compared to control roots. This study applies knowledge gained from the model system, Arabidopsis, to soybean to confer partial resistance to SCN. These studies are of interest to scientists and industry, because some of these genes confer resistance to SCN, and they may be useful in engineering broad resistance in soybean to nematodes.
Technical Abstract: Background. Extensive studies using the model system Arabidopsis thaliana to elucidate plant defense signaling and pathway networks indicate that salicylic acid (SA) is the key hormone triggering the plant defense response against biotrophic and hemi-biotrophic pathogens, while jasmonic acid (JA) and derivatives are critical to the defense response against necrotrophic pathogens. Several reports demonstrate that SA limits nematode reproduction. Results. Here we investigate the role of thirty-one genes encoding important components of SA and JA synthesis and signaling in conferring resistance to soybean cyst nematode. We demonstrate that overexpression of six of thirty-one Arabidoposis genes in transgenic soybean roots of composit plants decreased the number of cysts formed by the soybean cyst nematode (SCN: Heterodera glycines) 35 days after inoculation. Overexpression of three Arabidopsis genes decreased the number of cysts to less than 50% of those found on control roots, namely AtNPR1(33%), AtAHBP (38%), and AtPR-5 (38%). Three additional Arabidopsis genes decreased the number of SCN cysts by 40% or more: AtACBP3 (53% of the control value), AtACD2 (55%), and AtCM-3 (57%). Other genes having less or no effect included AtEDS5 (77%), AtNDR1 (82%), AtEDS1 (107%), and AtPR-1 (80%), as compared to control. Overexpression of AtDND1 greatly increased susceptibility as indicated by a large increase in the number of SCN cysts (175% of control). Conclusions. Our results show that overexpression of Arabidopsis genes encoding specific components involved in SA regulation, synthesis, and signaling can confer resistance or increase susceptibility to SCN in soybean.