Overexpression of GmPAL genes enhance soybean resistance against Heterodera glycines .

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. Isolavonoids are secondary metabolites of the phenylalanine pathway, and which are synthesized mainly 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 isoflavonoids biosynthesis, can positively regulate soybean resistance to SCN. Our previous study demonstrated that the expression of GmPAL genes in 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 demonstrated that the resistance of soybeans against SCN were 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 which are daidzein and genistein could enhance resistance against SCN and suppress nematode development. The study thus reveals GmPAL-mediated resistance against SCN, an information that has good application potential. The role of isoflavones in soybean resistance provides a new idea for the control of SCN.