Functional conservation of the grapevine candidate gene INNER NO OUTER for ovule development and seed formation

Seedlessness represents a highly appreciated trait in table grapes. Based on an interesting case of seedless fruitproduction described in the crop species Annona squamosa, we focused on the Vitis vinifera INNER NO OUTER (INO)gene as a candidate. This gene encodes a transcription factor belonging to the YABBY family involved in thedetermination of abaxial identity in several organs. In Arabidopsis thaliana, this gene was shown to be essential for theformation and asymmetric growth of the ovule outer integument and its mutation leads to a phenotypic defect ofovules and failure in seed formation. In this study, we identified in silico the V. vinifera orthologue and investigated itsphylogenetic relationship to INO genes from other species and its expression in different organs in seeded andseedless varieties. Applying cross-species complementation, we have tested its functionality in the Arabidopsis ino-1mutant. We show that the V. vinifera INO successfully rescues the ovule outer integument growth and seeds set andalso partially complements the outer integument asymmetric growth in the Arabidopsis mutant, differently fromorthologues from other species. These data demonstrate that VviINO retains similar activity and protein targets ingrapevine as in Arabidopsis. Potential implications for grapevine breeding are discussed.