Abstract

GA 2-oxidases regulate gibberellin levels in ovaries and axillary buds of tomato plants and their silencing is responsible for parthenocarpic fruit growth and branching inhibition.Gibberellins (GAs) are phytohormones that regulate a wide range of developmental processes in plants. Levels of active GAs are regulated by biosynthetic and catabolic enzymes like the GA 2-oxidases (GA2oxs). In tomato (Solanum lycopersicum L.) C-19 GA2oxs are encoded by a small multigenic family of five members with some degree of redundancy. In order to investigate their roles in tomato, the silencing of all five genes in transgenic plants was induced. A significant increase in active GA(4) content was found in the ovaries of transgenic plants. In addition, the transgenic unfertilized ovaries were much bigger than wild-type ovaries (about 30 times) and a certain proportion (5-37%) were able to develop parthenocarpically. Among the GA2ox family, genes GA2ox1 and -2 seem to be the most relevant for this phenotype since their expression was induced in unfertilized ovaries and repressed in developing fruits, inversely correlating with ovary growth. Interestingly, transgenic lines exhibited a significant inhibition of branching and a higher content of active GA(4) in axillary buds. This phenotype was reverted, in transgenic plants, by the application of paclobutrazol, a GA biosynthesis inhibitor, suggesting a role for GAs as repressors of branching. In summary, this work demonstrates that GA 2-oxidases regulate gibberellin levels in ovaries and axillary buds of tomato plants and their silencing is responsible for parthenocarpic fruit growth and branching inhibition.

Keywords

Branching; GA 2-oxidases; gibberellins; parthenocarpy; silencing; tomato

Published in

Journal of Experimental Botany
2015, Volume: 66, number: 19, pages: 5897-5910
Publisher: OXFORD UNIV PRESS

SLU Authors

• Moritz, Thomas

  • Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Developmental Biology
Botany


Publication identifier

DOI: https://doi.org/10.1093/jxb/erv300

Permanent link to this page (URI)

https://res.slu.se/id/publ/73943