Specific mediators of auxin activity during tomato leaf and fruit development

Abstract

The plant hormone auxin is involved in numerous developmental processes, including leaf and fruit development. The tomato (Solanumlycopersicum) gene ENTIRE (E) encodes an auxin-response inhibitor from the Aux/IAA family. While most loss-offunction mutations in Aux/IAA genes are similar to the wild type due to genetic redundancy, entire (e) mutants show specific effects on leaf and fruit development. e mutants have simple leaves, in contrast to the compound leaves of wild type tomatoes. In addition, e plants produce parthenocarpic fruits, in which fruit set occurs independently of fertilization. The aim of this research program was to utilize the e mutation to identify and characterize genes that mediate the specific effect of auxin in leaf and fruit development. The specific objectives of the project were to: 1. Characterize and map modifiers of the e leaf phenotype. 2. Characterize and map suppressors of the e fruit phenotype. 3. Dissect the developmental specificity of the E gene. 4. Examine the effect of fruit-overexpression of identified genes on fruit set and seed production. To identify mediators of auxin in leaf development, we mainly focused on one mutant, crawling elephant (crel, previously called t282), which showed substantial suppression of the e phenotype and other auxin-relatedphenotypes. We have identified the CREL gene as a homolog of the Arabidopsis VRN5 gene, involved in recruiting polycomb silencing complexes to specific targets. We showed that CREL affects auxin sensitivity in tomato. Suppressors of the e fruit phenotype have been further characterized and selected for more profound effects. Expression profiling by RNAseq was used to analyze the effect of e as well as crel on gene expression in leaves and fruits. This analysis has identified putative E and CREL targets. We have initiated studies to assess the role of some of these targets in flower and fruit development. The research has identified potential mediators of auxin response in leaf, flower and fruit development.