Journal Article

The Tomato Aux / IAA Transcription Factor IAA9 Is Involved in Fruit Development and Leaf Morphogenesis

Frasse, Pierre, Regad, Farid, Delalande, Corinne, Latché, Alain, Li, Zhengguo, Pech, Jean-Claude, Jones, Brian, Chaabouni, Salma, École nationale supérieure agronomique de Toulouse (ENSAT) ; Institut National Polytechnique (Toulouse) (Toulouse INP) ; Université de Toulouse (UT)-Université de Toulouse (UT), Wang, Hua, Bouzayen, Mondher

2005

Overview

Auxin/indole-3-acetic acid (Aux/IAA) proteins are transcriptional regulators that mediate many aspects of plant responses to auxin. While functions of most Aux/IAAs have been defined mainly by gain-of-function mutant alleles in Arabidopsis thaliana, phenotypes associated with loss-of-function mutations have been scarce and subtle. We report here that the downregulation of IAA9, a tomato (Solanum lycopersicum) gene from a distinct subfamily of Aux/IAA genes, results in a pleiotropic phenotype, consistent with its ubiquitous expression pattern. IAA9-inhibited lines have simple leaves instead of wild-type compound leaves, and fruit development is triggered before fertilization, giving rise to parthenocarpy. This indicates that IAA9 is a key mediator of leaf morphogenesis and fruit set. In addition, antisense plants displayed auxin-related growth alterations, including enhanced hypocotyl/stem elongation, increased leaf vascularization, and reduced apical dominance. Auxin dose-response assays revealed that IAA9 downregulated lines were hypersensitive to auxin, although the only early auxin-responsive gene that was found to be upregulated in the antisense lines was IAA3. The activity of the IAA3 promoter was stimulated in the IAA9 antisense genetic background, indicating that IAA9 acts in planta as a transcriptional repressor of auxin signaling. While no mutation in any member of subfamily IV has been reported to date, the phenotypes associated with the downregulation of IAA9 reveal distinct and novel roles for members of the Aux/IAA gene family.

• Publisher: American Society of Plant Biologists (ASPB),HAL CCSD,American Society of Plant Biologists
• Subject: Acetic acid / antisense DNA / Arabidopsis thaliana / Auxins / Conserved Sequence / Conserved Sequence - genetics / DNA-Binding Proteins / DNA-Binding Proteins - genetics / DNA-Binding Proteins - metabolism / Down regulation / Down-Regulation - drug effects / Down-Regulation - genetics / drug effects / Fruit / Fruit - genetics / Fruit - growth & development / Fruit - metabolism / Fruit set / fruiting / Fruits / gene expression regulation / Gene Expression Regulation, Plant / Gene Expression Regulation, Plant - drug effects / Gene Expression Regulation, Plant - genetics / Genes / Genetic mutation / genetics / growth & development / IAA9 gene / Indoleacetic Acids / Indoleacetic Acids - metabolism / Indoleacetic Acids - pharmacology / leaf development / Leaves / Life Sciences / Lycopersicon esculentum / Lycopersicon esculentum - genetics / Lycopersicon esculentum - growth & development / Lycopersicon esculentum - metabolism / metabolism / Molecular Sequence Data / morphogenesis / mutants / Mutation / nucleotide sequences / pharmacology / Phenotype / Phenotypes / Phylogeny / plant growth / Plant Growth Regulators / Plant Growth Regulators - genetics / Plant Growth Regulators - metabolism / Plant Leaves / Plant Leaves - genetics / Plant Leaves - growth & development / Plant Leaves - metabolism / Plant Proteins / Plant Proteins - genetics / Plant Proteins - metabolism / Plant roots / Plants / pleiotropy / Promoter Regions, Genetic / Promoter Regions, Genetic - genetics / Sequence Homology, Amino Acid / Signal Transduction / Signal Transduction - drug effects / Signal Transduction - genetics / Silencer Elements, Transcriptional / Silencer Elements, Transcriptional - genetics / Solanum / Solanum lycopersicum / Solanum lycopersicum var. lycopersicum / Tomatoes / transcription (genetics) / transcription factors / Transcription Factors - genetics / Transcription Factors - metabolism / transgenic plants / Vegetal Biology