Soybean cyst nematode ( Heterodera glycines, soybean cyst nematode [SCN]) disease adversely affects the yield of soybean and leads to billions of dollars in losses every year. To control the disease, it is necessary to study the resistance genes of the plant and their mechanisms. Isoflavonoids are secondary metabolites of the phenylalanine pathway, and they are synthesized in soybean. They are essential in plant response to biotic and abiotic stresses. In this study, we reported that phenylalanine ammonia-lyase (PAL) genes GmPALs involved in isoflavonoid biosynthesis, can positively regulate soybean resistance to SCN. Our previous study demonstrated that the expression of GmPAL genes in the resistant cultivar Huipizhi (HPZ) heidou are strongly induced by SCN. PAL is the rate-limiting enzyme that catalyzes the first step of phenylpropanoid metabolism, and it responds to biotic or abiotic stresses. Here, we demonstrate that the resistance of soybeans against SCN is suppressed by PAL inhibitor l-α-(aminooxy)-β-phenylpropionic acid (L-AOPP) treatment. Overexpression of eight GmPAL genes caused diapause of nematodes in transgenic roots. In a petiole-feeding bioassay, we identified that two isoflavones, daidzein and genistein, could enhance resistance against SCN and suppress nematode development. This study thus reveals GmPAL-mediated resistance against SCN, information that has good application potential. The role of isoflavones in soybean resistance provides new information for the control of SCN. [ ] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Background: The yield of soybean is limited by the soybean cyst nematode (SCN, Heterodera glycines). Soybean transformation plays a key role in gene function research but the stable genetic transformation of soybean usually takes half a year. Methods: Here, we constructed a vector, pNI-GmUbi, in an Agrobacterium rhizogenes-mediated soybean hypocotyl transformation to induce fluorescent hairy roots (FHRs). Results: We describe the operation of FHR-SCN, a fast, efficient and visual operation pathosystem to study the gene functions in the soybean-SCN interaction. With this method, FHRs were detected after 25 days in 4 cultivars (Williams 82, Zhonghuang 13, Huipizhiheidou and Peking) and at least 66.67% of the composite plants could be used to inoculate SCNs. The demographics of the SCN could be started 12 days post-SCN inoculation. Further, GmHS1^pro-1 was overexpressed in the FHRs and GmHS1^pro-1 provided an additional resistance in Williams 82. In addition, we found that jasmonic acid and JA-Ile increased in the transgenic soybean, implying that the resistance was mainly caused by affecting the content of JA and JA-Ile. Conclusions: In this study, we established a pathosystem, FHR-SCN, to verify the functional genes in soybeans and the SCN interaction. We also verified that GmHS1^pro-1 provides additional resistance in both FHRs and transgenic soybeans, and the resistance may be caused by an increase in JA and JA-Ile contents.