| The spr2 tomato line carries a point mutation that eliminates function of a fatty acid desaturase, FAD7, resulting in higher linoleic acid (LA), lower linolenic acid (LNA), and impaired jasmonic acid (JA) biosynthesis. This study utilized spr2 to investigate the impact of FAD7 on two agriculturally important traits: aphid resistance in the foliage and antioxidant content in the fruits. We report here that the spr2 mutation reduced aphid host preference and aphid population growth. In addition, aphid feeding in spr2 caused a dramatic increase in accumulation of salicylic acid (SA), and introgression of the NahG transgene, which inhibits SA accumulation, restored wild-type levels of aphid susceptibility in spr2. Aphid feeding on the spr2 mutant also upregulated transcription of alpha-dioxygenase 1 ( alpha-DOX1), a gene involved in the synthesis of oxylipins from LA and LNA, and virus-induced gene silencing of alpha-DOX1 restored wild-type levels of aphid susceptibility in spr2. These results suggest that FAD7 influences plant defenses against aphids by regulating both the SA and oxylipin metabolism pathways. The spr2 mutation also influenced antioxidant content in tomato fruits, decreasing lycopene but increasing vitamin C. This effect on antioxidants may be mediated by the effect of the spr2 mutation on JA production, because post-harvest treatment of JA to fruits of certain cultivars enhanced the lycopene, antioxidant capacity, and the phenolic content. These results suggest a role of JA in regulating the synthesis of antioxidants in tomato, and the potential for post-harvest JA treatments to improve the nutritional quality of certain tomato cultivars. |
