These authors contributed equally to this work.
Auxin-induced fruit-set in tomato is mediated in part by gibberellins
Article first published online: 11 SEP 2008
© 2008 The Authors. Journal compilation © 2008 Blackwell Publishing Ltd
The Plant Journal
Volume 56, Issue 6, pages 922–934, December 2008
How to Cite
Serrani, J. C., Ruiz-Rivero, O., Fos, M. and García-Martínez, J. L. (2008), Auxin-induced fruit-set in tomato is mediated in part by gibberellins. The Plant Journal, 56: 922–934. doi: 10.1111/j.1365-313X.2008.03654.x
- Issue published online: 8 DEC 2008
- Article first published online: 11 SEP 2008
- Received 10 May 2008; revised 30 July 2008; accepted 5 August 2008; published online 11 September 2008.
- auxin response factors;
- GA metabolism;
Tomato (Solanum lycopersicum L.) fruit-set and growth depend on gibberellins (GAs). Auxins, another kind of hormone, can also induce parthenocarpic fruit growth in tomato, although their possible interaction with GAs is unknown. We showed that fruit development induced by the auxins indole-3-acetic acid and 2,4-dichlorophenoxyacetic acid (2,4-D) were significantly reduced by the simultaneous application of inhibitors of GA biosynthesis, and that this effect was reversed by the application of GA3. This suggested that the effect of auxin was mediated by GA. Parthenocarpic fruits induced by 2,4-D had higher levels of the active GA1, its precursors and metabolites, than unpollinated non-treated ovaries, but similar levels as those found in pollinated ovaries. Application experiments of radioactive-labelled GAs to unpollinated ovaries showed than 2,4-D altered GA metabolism (both biosynthesis and catabolism) in vivo. Transcript levels of genes encoding copalyldiphosphate synthase (SlCPS), SlGA20ox1, SlGA20ox2 and SlGA20ox3, and SlGA3ox1 were higher in unpollinated ovaries treated with 2,4-D. In contrast, transcript levels of SlGA2ox2 (out of the five SlGA2ox genes known to encode this kind of GA-inactivating enzyme) were lower in ovaries treated with 2,4-D. Our results support the idea that auxins induce fruit-set and growth in tomato, at least partially, by enhancing GA biosynthesis (GA 20-oxidase, GA 3-oxidase and CPS), and probably by decreasing GA inactivation (GA2ox2) activity, thereby leading to higher levels of GA1. The expression of diverse Aux/indole-3-acetic acid (IAA) and auxin response factors, which may be involved in this effect of auxin, was also altered in 2,4-D-induced ovaries.