Colonization of <i>Piriformospora indica</i> enhances insect herbivore resistance of rice plants through jasmonic acid- and antioxidant-mediated defense mechanisms

<i>Piriformospora indica</i> (<i>P. indica</i>) is a mutualistic endophyte that colonizes plant roots. In this study, effects of <i>P. indica</i> on rice resistance against rice leaffolder (<i>Cnaphalocrocis medinalis</i> Guenée) were investigated. Growth inhibition and leaf injury caused by leaffolder larvae infestation in <i>P. indica</i>-colonized rice was significantly alleviated. Moreover, growth retardation was observed in larvae which fed on <i>P. indica</i>-colonized plants. JA-Ile levels and trypsin inhibitor activities in leaf tissues of <i>P. indica</i>-colonized plants were higher than those in noncolonized plants under leaffolder-infested conditions. <i>P. indica</i> effects on increasing trypsin inhibitor expression and reducing larval growth were repressed by aspirin. JA signaling drives <i>P. indica</i>-enhanced insect resistance in rice, and trypsin inhibitors might be candidates involved in this mechanism. Changes in antioxidant enzyme activities and malondialdehyde levels in <i>P. indica</i>-inoculated plants were observed, and it was demonstrated that oxidative stress induced by insect infestation could be reduced in <i>P. indica</i>-colonized plants.