Jasmonoyl-L-isoleucine hydrolase 1 (JIH1) contributes to a termination of jasmonate signaling in Nicotiana attenuata

The jasmonate signaling pathway is essential for plant development, reproduction, and defense against herbivores and pathogens. When attacked by herbivores, plants elicit defense responses through the rapid accumulation of jasmonates. Although the transduction of the jasmonate burst into downstream responses has been largely resolved in the past decade, how the jasmonate burst is switched off remained unknown. Recently, two mechanisms that involve cytochrome p450-mediated hydroxylation/carboxylation and NaJIH 1-mediated hydrolysis of JA-Ile were identified as major termination mechanisms of JA signaling. Due to a lack of hydrolysis, Nicotiana attenuata plants silenced in the expression of the JIH1 gene accumulated significantly more JA-Ile than did wild type plants and became more resistant to herbivore attack. Although less likely, additional functions of JIH 1, such as contributing to the pool of free Ile and thereby increasing JA-Ile accumulation, remained untested. Here we show that increased isoleucine availability does not explain the observed phenotype in JIH 1-deficient N. attenuata plants