Jasmonic Acid Mediates Tomato’s Response to Root Knot Nematodes

Jasmonates such as jasmonic acid (JA) are plant-signaling compounds that induce resistance to a broad range of herbivores. JA-dependent defenses are known to reduce the growth and survivorship of many insects. How plants coordinate fluctuating growth-defense dynamics is not well understood with regard to the role of JA in resistance to tomato root knot nematodes (RKN). To better understand JA-mediated nematode resistance, the average root nodules per hill were compared among CM(WT), JA biosynthetic mutant (spr2), 35S::prosystemin(35S::PS), indicating that in the mutant line 35S::PS, JA overexpressed transgenic tomato, the proteinase inhibitor II (PI-II) translation level gradually increased with time after inoculation with RKN. This was accompanied by the production of phytohormones such as JA to enclose the invading nematodes at the initial site of infection, and then inhibit nematode multiplication and spread. The JA synthesis mutant, spr2, could not induce high expression of PI-II in the leaf while the root system was susceptible to nematodes. Exogenous JA on the shoots of spr2 can induce a strong systemic defense response in the roots, as exemplified by a major up-regulation of phospholipase A₂(PLA₂) and PI-II, indicating that methyl jasmonate (MeJA) had a positive impact on spr2 survivorship. The expression profiles of 14 systemin/JA-related genes were evaluated by quantitative real-time PCR profiling, which revealed that the corresponding genes participate directly or indirectly in tomato plants after vaccination with RKN. The results indicated that the observed effects of both endogenous and exogenous JA on RKN resistance were involved in the JA pathway.