Identification of naturally-occurring polyamines as nematode Meloidogyne incognita attractants.

Root-knot nematodes (RKN, genus Meloidogyne) are a class of plant parasites that seek out and infect roots of many plant species. It is believed that RKN 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 compound for M. incognita attractants. Break-down product of aminopropylamino-anthraquinone, 1,3-diaminopropane, as well as related compounds putrescine and cadaverine were found to attract M. incognita. After examining various polyamines, M. incognita were found to be attracted specifically by natural compounds that possess three to five methylene groups between two terminal amino groups. Using cryo-TOF-SIMS/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-diaminopropane were also detected in root exudate by HPLC-MS/MS. Furthermore, exogenously applied cadaverine is sufficient to enhance M. incognita infection of Arabidopsis seedlings. These results suggest M. incognita may indeed target polyamines to locate the appropriate host plants, and these naturally-occurring polyamines may have viable applications in agriculture to develop protection strategies for crops from RKN infections.