Molecular mechanisms underlying the early steps of floral initiation in seasonal flowering genotypes of cultivated strawberry

Freya Maria Rosemarie Ziegler^1,2*Amèlia Gaston³Karine Guy⁴Marie Devers³Erika Krüger⁵Bastienne Brauksiepe⁶Klaus Eimert⁵Sonia Osorio⁷Béatrice Denoyes^3*Björn Usadel^1,2*

• ¹Forschungszentrum Jülich, Institute of Bio- and Geosciences, IBG-4 Bioinformatics, BioSC, Jülich, Germany
• ²Heinrich-Heine University of Düsseldorf, Faculty of Mathematics and Natural Sciences, Institute for Biological Data Science, CEPLAS, Düsseldorf, Germany
• ³Université de Bordeaux, INRAE, Biologie du Fruit et Pathologie, Bordeaux, France
• ⁴INVENIO, MIN de Brienne, Bordeaux, France
• ⁵Hochschule Geisenheim University, Department of Pomology, Geisenheim, Germany
• ⁶Hochschule Geisenheim University, Department of Molecular Plant Science, Geisenheim, Germany
• ⁷Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Instituto de 18 Hortofruticultura Subtropical y Mediterránea “La Mayora”, Departamento de Biología Molecular y 19 Bioquímica, Malaga, Spain

Floral initiation is essential for sexual reproduction in angiosperms and plays a critical role in determining crop yields. In cultivated strawberry, however, the molecular mechanisms underlying floral initiation remain poorly understood, with most studies focusing on a single genotype under controlled conditions. To gain more insight into this process, we conducted a field-based study in two countries using two seasonal flowering cultivars. Our investigation focused on the early stages of floral initiation, analysing samples that captured key developmental stages of the shoot apical meristem. Differential gene expression analysis of leaf and terminal bud tissues revealed an enrichment of genes involved in carbohydrate metabolism and phytohormone signaling pathways in leaves. Additionally, we observed enrichment of protein classes related to cytoskeleton organization, cell cycle regulation, and chromatin structure during early floral initiation. We also identified genes associated with the photoperiodic pathway, including well-known floral integrators such as TFL1 and SOC1, along with several other genes linked to phytohormone regulation, such as XTH23, PP2 and EIN3.