Gibberellins modulate auxin responses during tomato ( Solanum lycopersicum L.) fruit development
MIGNOLLI, FRANCESCO; VIDOZ, MARIA L.; PICCIARELLI, PIERO; MARIOTTI, LORENZO
WILEY-BLACKWELL PUBLISHING, INC
In tomato, auxin and gibberellins (GAs) interact with each other to drive fruit growth anddevelopment. While the role of auxin in directing GA biosynthesis and signal is already known,very little information has been obtained about GA-mediated control of auxin signalling andresponse. Interestingly, we show that GA3 is able to modify the expression of several auxinsignalling genes in the partial auxin-insensitive diageotropica (dgt) mutant, suggesting that GAsmay override the control of DGT on auxin signal. Procera (pro) mutation, which confers aconstitutively active GA signal, enhances the effects of exogenous auxin, indicating that PRO mayact as a negative effector of auxin responses in fruits. Indeed, transcript modulation of someAux/IAA and ARF genes in auxin-treated dgt/pro fruits, suggests that PRO controls theirexpression possibly bypassing DGT. It was also shown that GA biosynthesis, in response to auxintreatment, is largely controlled by DGT. It is therefore conceivable that the DGT-mediated increaseof active GAs in auxin-treated or pollinated fruits, would promote PRO degradation, which in turnactivates part of the auxin signalling cascade.