An (E,E)-a-farnesene synthase gene of soybean has a role in defense against nematodes and is involved in synthesizing insect-induced volatiles

Authors: LIN, JINGYU - University Of Tennessee; WANG, DAN - Nankai University; CHEN, XINLU - University Of Tennessee; KOLLNER, TOBIAS - Max Planck Institute Of Chemical Ecology; MAZAREI, MITRA - University Of Tennessee; GUO, HONG - University Of Tennessee; PANTALONE, VINCE - University Of Tennessee; Arelli, Prakash; STEWART, JR, NEAL - University Of Tennessee; WANG, NING-NING - Nankai University; CHEN, FENG - University Of Tennessee

Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2016
Publication Date: 4/1/2017
Citation: Lin, J., Wang, D., Chen, X., Kollner, T., Mazarei, M., Guo, H., Pantalone, V., Arelli, P.R., Stewart, Jr, N., Wang, N., Chen, F. 2017. An (E,E)-a-farnesene synthase gene of soybean has a role in defense against nematodes and is involved in synthesizing insect-induced volatiles. Plant Biotechnology Journal. 15 (4)510-519.

Interpretive Summary: Soybean yields worldwide are limited by the soybean cyst nematode (SCN), a microscopic size roundworm attaching the roots and absorbing the nutrition from the soybean plant. Resistant cultivars have been the most effective means of controlling the pest. Nematode populations are highly variable and over time will adapt to reproduce on resistant cultivars rendering once resistant a susceptible one. Traditional breeding methods combined with modern genetic engineering technology should be developed for rapid identification and deployment of novel resisitance genes for durable resistance to SCN. Soybean TPS gene family, designated as GmAFS have roles in several biological processes. In complex molecular genetic tests the expression of GmAFS in a SCN-resistant soybean was significantly higher when the soybean plant was infected with SCN compared to non-infected soybean plant and was similar to spider mites attacked plants. This breakthrough can help to genetically engineered soybean plants for higher expression of GmAFS and thus to protect plants from nematode and spider mites attacks. One more tool to protect soybeans from both spider mites and SCN and increase yields to soybean growers and this will result in higher profits and contribute to sustainable soybean production.

Technical Abstract: Plant terpene synthase genes (TPSs) have roles in diverse biological processes. Here we report the functional characterization of one member of the soybean TP S gene family, which was designated GmAFS. Recombinant GmAFS produced in E.coli catalyzed the formation of a sesquiterpene (E,E)-a-farnesene. GmAFS is closely related to (E,E)-a-farnesene synthase genes from apple, both phylogenetically and structurally. GmAFS was further investigated for its biological role in defense against nematodes and insects. Soybean cyst nematode (SCN) is the most important pathogen of soybean. The expression of GmAFS in a SCN-resistant soybean was significantly induced by SCN infection compared to the control, whereas its expression in a SCN-susceptible soybean was not changed by SCN infection. Transgenic hairy roots overexpressing GmAFSunder the control of the CaMV 35S promoter were generated in an SCNsusceptible soybean breeding line. The transgenic lines showed significantly higher resistance to SCN, which indicates that GmAFS contributes to the resistance of soybean to SCN. In soybean leaves, the expression of GmAFS was found to be induced by spider mites. Exogenous application of methyl jasmonate to soybean plants also induced the expression of GmAFS in leaves. Using headspace collection combined with gas chromatography-mass spectrometry analysis, soybean plants that were infested with spider mites emitted a mixture of volatiles with (E,E)-a-farnesene as one of the most abundant constituents. In summary, this study showed GmAFS has defense roles in both below-ground and above-ground organs of soybean against nematodes and insects, respectively.