Controllo ormonale nella formazione del frutto di pomodoro: interazioni molecolari e profili metabolici
Author(s)
Mignolli, Francesco
Date Issued
March 18, 2011
Type
Doctoral Thesis
Abstract
Tomato (Solanum lycopersicum Mill.) fruit set depends on successful pollination and
fertilization that trigger auxin and gibberellin signalling pathways. However, the exact role of
these two hormones and the precise mechanism of interaction is still partially unknown. In
order to dissect the cross-talk between auxin and gibberellins during fruit development, we
performed experiments with two tomato mutants, diageotropica (dgt) and entire (e), altered
for genes involved in auxin signalling. While tomato dgt mutant, characterised by a mutated
cyclophilin gene, is auxin-resistant, the tomato entire mutant lacks an auxin response
repressor, making this mutant hyper-responsive to the hormone. Endogenous gibberellins
determination and gene expression analysis revealed that DGT and entire (LeIAA9) genes may
be involved in regulating the expression of gibberellin biosynthesis genes in the tomato fruit.
DGT seems to positively control the expression of GA20ox gene family and to inhibit the
inactivation of GA20 through its conversion into GA29. Conversely, the entire mutation
produces seedless (parthenocarpic) fruits and enhances the transcript accumulation of
GA20ox-1. All these data corroborate the hypothesis of a role for the auxin signal as regulator
of gibberellin biosynthesis trough the GA20oxidases. In addition, we propose that a
quantitative relationship between auxin perception and gibberellin metabolism is established
during the ovary development. Our data support the idea of an interaction between auxin and
gibberellins in the regulation of cell division, cell expansion and cell endoreduplication in fruit
tissues. The auxin signal appears particularly involved in locular tissue development.
Furthermore, our findings suggest that gibberellins contribute to modulate the auxin
response by modifying the expression of some genes involved in auxin signalling.
Additional information
Dottorato di ricerca in Biotecnologie vegetali
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