Tomato lipoxygenase D involved in the biosynthesis of jasmonic acid and tolerance to abiotic and biotic stress in tomato

TomloxD is a lipoxygenase from Lycopersicon esculentum Mill, which has lipoxygenase activity. The expression of TomloxD can be stimulated by wounding, pathogen infection, jasmonate, and systemin. To investigate the function of TomloxD, transgenic tomato plants silencing tomloxD gene was produced. The suppression of TomloxD expression led to a marked reduction in the levels of lipoxygenase activity and endogenous jasmonic acid content, which suggested TomloxD can catalyze α-linolenic acids to produce (13S)-hydroperoxyoctadecatrienoic acid (13-HPOT), and the 13-HPOT is metabolized further to synthesize jasmonic acid. Real-time RT-PCR revealed that the expression of defense genes LeHSP90, LePR1 and LePR6 was also less in the transformants than in the wild-type tomato plant. Resistance assay showed that the suppression of TomloxD in transgenic tomato plants reduced thermotolerance of tomato and increased its susceptibility to Cladosporium fulvum. Collectively, the data presented here suggest that the TomloxD plays a role as a component of the octadecanoid defense-signaling pathway and involved in the generation of endogenous jasmonic acid, and in turn regulates the expression of plant defense genes and resistance to high temperature and pathogen attack.