Phenotypes associated with down-regulation of Sl-IAA27 support functional diversity among Aux/IAA family members in tomato.
2012
Bassa, Carole | Mila, Isabelle | Bouzayen, Mondher | Audran-Delalande, Corinne
The phytohormone auxin is known to regulate several aspects of plant development and Aux/IAA transcription factors play a pivotal role in auxin signaling. To further extend our understanding of the multiple functions of Aux/IAAs, the present study describes the functional characterization of Sl-IAA27, a member of the tomato Aux/IAA gene family. Sl-IAA27 displays a distinct behavior compared to most Aux/IAA regarding the regulation of its expression by auxin and the Sl-IAA27 encoded protein harbors a unique motif of unknown function also present in Sl-IAA9 and remarkably conserved in monocot and dicot species. Tomato transgenic plants under-expressing the Sl-IAA27 gene revealed multiple phenotypes related to vegetative and reproductive growth. Silencing of Sl-IAA27 results in higher auxin sensitivity, altered root development and reduced chlorophyll content in leaves. Both ovule and pollen display dramatic loss of fertility in Sl-IAA27 down-regulated lines and the internal anatomy of the flower and the fruit are modified with enlarged placenta in smaller fruits. In line with the reduced chlorophyll content in Sl-IAA27 RNAi leaves, genes involved in chlorophyll synthesis display lower expression at the level of transcript accumulation. Even though Sl-IAA27 is closely related to Sl-IAA9 in terms of sequence homology and the encoded proteins share common structural features, the data indicate that the two genes regulate tomato fruit initiation and development in a distinct manner.
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