Location: Agroecosystem Management ResearchTitle: Overexpression of a soybean salicylic acid methyltransferase gene confers resistance to soybean cyst nematode Author
|Zhu, Junwei - Jerry|
Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2013
Publication Date: 12/1/2013
Publication URL: http://handle.nal.usda.gov/10113/59421
Citation: Lin, J., Mazarei, M., Zhao, N., Zhu, J.J., Zhuang, X., Liu, W., Pantalone, V., Arelli, P.R., Stewart, C.N., Feng, C. 2013. Overexpression of a soybean salicylic acid methyltransferase gene confers resistance to soybean cyst nematode. Plant Biotechnology Journal. 11(9):1135-1145. DOI: 10.1111/PBI.12108. Interpretive Summary: Soybean cyst nematode (Heterodera glycines, SCN), a sedentary obligate endoparasite, is one of the most devastating pests of soybean, Glycine max (L.) Merr. Crop rotation and application of nematicides have been used to control SCN but with limited success. Deployment of SCN-resistant soybean varieties is another important component of SCN management, which however is often challenged by the frequent changes in population virulence of SCN. To expedite the continued development of new SCN-resistant soybean varieties, it is important to isolate resistant genes from various resistance sources of soybean and elucidate the defense mechanisms. Our study showed that GmSAMT1 functions as S-adenosyl-L-methionine-dependent salicylic acid methyltransferase, catalyzing the formation of methyl salicylate using salicylic acid as substrate. Using transgenic hairy roots, GmSAMT1 was demonstrated to have a role in the resistance of soybean plants against SCN.
Technical Abstract: Salicylic acid plays a critical role in activating plant defence responses after pathogen attack. Salicylic acid methyltransferase (SAMT) modulates the level of salicylic acid by converting salicylic acid to methyl salicylate. Here, we report that a SAMT gene from soybean (GmSAMT1) plays a role in soybean defence against soybean cyst nematode (Heterodera glycines Ichinohe, SCN). GmSAMT1 was identified as a candidate SCN defence-related gene in our previous analysis of soybean defence against SCN using GeneChip microarray experiments. The current study started with the isolation of the full-length cDNAs of GmSAMT1 from a SCN-resistant soybean line and from a SCN-susceptible soybean line. The two cDNAs encode proteins of identical sequences. The GmSAMT1 cDNA was expressed in Escherichia coli. Using in vitro enzyme assays, E. coliexpressed GmSAMT1 was confirmed to function as salicylic acid methyltransferase. The apparent Km value of GmSAMT1 for salicylic acid was approximately 46 lM. To determine the role of GmSAMT1 in soybean defence against SCN, transgenic hairy roots overexpressing GmSAMT1 were produced and tested for SCN resistance. Overexpression of GmSAMT1 in SCN-susceptible backgrounds significantly reduced the development of SCN, indicating that overexpression of GmSAMT1 in the transgenic hairy root system could confer resistance to SCN. Overexpression of GmSAMT1 in transgenic hairy roots was also found to affect the expression of selected genes involved in salicylic acid biosynthesis and salicylic acid signal transduction.