The gene pat-2, which induces natural parthenocarpy, alters the gibberellin content in unpollinated tomato ovaries

We investigated the role of gibberellins (CAs) in the effect of pat-2 a rec essive mutation that induces facultative parthenocarpic fruit development i n tomato (Lycopersicon esculentum Mill.) using near-isogenic lines with two different genetic backgrounds. Unpollinated wild-type Madrigal (MA/wt) and Cuarenteno (CU/wt) ovaries degenerated, but GA(3) application induced part henocarpic fruit growth. On the contrary, parthenocarpic growth of MA/pat-2 and CU/pat-2 fruits, which occurs in the absence of pollination and hormon e application, was not affected by GA(3). Pollinated MA/wt and parthenocarp ic MA/pat-2 ovary development was negated by paclobutrazol, and this inhibi tory effect was counteracted by CA(3). The main CAs of the early-13-hydroxy lation pathway (GA(1), GA(3), GA(8), GA(19), GA(20), GA(29), GA(44), GA(53) , and, tentatively, GA(81)) and two CAs of the non-13-hydroxylation pathway (GA(9) and GA(34)) were identified in MA/wt ovaries by gas chromatography- selected ion monitoring. CAs were quantified in unpollinated ovaries at flo wer bud, pre-anthesis, and anthesis. In unpollinated MA/pat-2 and CU/pat-2 ovaries, the GA(20) content was much higher (up to 160 times higher) and th e GA(19) content was lower than in the corresponding non-parthenocarpic ova ries. The application of an inhibitor of 2-oxoglutarate-dependent dioxygena ses suggested that GA(20) is not active per se. The pat-2 mutation may incr ease CA 20-oxidase activity in unpollinated ovaries, leading to a higher sy nthesis of GA(20), the precursor of an active GA.