Identification of Naturally Occurring Polyamines as Root-Knot Nematode Attractants

Root-knot nematodes(RKNs;genus Meloidogyne)are a class of plant parasites that infect the roots of many plant species.It is believed that RKNs target certain signaling molecules derived from plants to locate their hosts;however,currently,no plant compound has been unambiguously identified as a universal RKN attractant.To address this question,we screened a chemical library of synthetic compounds for Meloidogyne incognita attractants.The breakdown product of aminopropylam ino-anthraquinone,1,3-diam inopropane,as well as its related compounds,putrescine and cadaverine,were found to attract M.incognita.After exam ining various polyamines,M.incognita were found to be attracted specifically by natural com pounds that possess three to five methylene groups between two terminal amino groups.Using cryo-TO F-SIM S/SEM,cadaverine was indeed detected in soybean root cortex cells and the surrounding rhizosphere,establishing a chemical gradient.In addition to cadaverine,putrescine and 1,3-diam inopropane were also detected in root exudate by HPLC-MS/MS.Furtherm ore,exogenously applied cadaverine is sufficient to enhance M.incognita infection of Arabidopsis seedlings.These results suggest that M.incognita is likely attracted by polyam ines to locate the appropriate host plants,and the naturally occurring polyamines have potential applications in agriculture in developing protection strategies for crops from RKN infection.