The gene pat-2, which induces natural parthenocarpy, alters the gibberellin content in unpollinated tomato ovaries.
We investigated the role of gibberellins (GAs) in the effect of pat-2, a recessive mutation that induces facultative parthenocarpic fruit development in 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 parthenocarpic fruit growth. On the contrary, parthenocarpic growth of MA/pat-2 and CU/pat-2 fruits, which occurs in the absence of pollination and hormone application, was not affected by GA(3). Pollinated MA/wt and parthenocarpic MA/pat-2 ovary development was negated by paclobutrazol, and this inhibitory effect was counteracted by GA(3). The main GAs of the early-13-hydroxylation pathway (GA(1), GA(3), GA(8), GA(19), GA(20), GA(29), GA(44), GA(53), and, tentatively, GA(81)) and two GAs of the non-13-hydroxylation pathway (GA(9) and GA(34)) were identified in MA/wt ovaries by gas chromatography-selected ion monitoring. GAs were quantified in unpollinated ovaries at flower 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 the GA(19) content was lower than in the corresponding non-parthenocarpic ovaries. The application of an inhibitor of 2-oxoglutarate-dependent dioxygenases suggested that GA(20) is not active per se. The pat-2 mutation may increase GA 20-oxidase activity in unpollinated ovaries, leading to a higher synthesis of GA(20), the precursor of an active GA.
Fos
M
M
Departamento de Biología Vegetal, Universidad Politécnica de Valencia, 46022-Valencia, Spain.
Nuez
F
F
García-Martínez
J L
JL
D017343:Genes, Plant; D005875:Gibberellins / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000235:genetics* / Q000378:metabolism / Q000502:physiology
D005875:Gibberellins