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Marie ALONSO

Team Flowering, Fruit Development and Environmental Constraints - FDFE

Thursday May 12, 2022 - 3:00 p.m. - ISVV Amphitheater - Campus INRAE Villenave d'Ornon

Abstract :

Strawberry is able to reproduce both sexually, via flowering, and asexually, via the production of stolons. The AxM governs these two modes of reproduction since AxM can become a lateral branch terminated by an inflorescence, or a stolon, or remain dormant. Thus, the AxM fate shapes the plant architecture and promotes the fruit yield or daughter plant production. The objective of this thesis is to identify and characterise molecular actors that affect the AxM fate by using the diploid strawberry model. The manuscript is divided into three points:

(1) Morphological and histological observation of the early events of the AxM development has allowed to define for the first time in strawberry a scale of the AxM development into a stolon or a lateral branch. This study highlights an undifferentiated stage that is morphologically identical for both types of AxM.

(2) A transcriptome study of undifferentiated axillary buds identified 283 differentially expressed genes (DEGs) between those becoming a stolon and becoming a lateral branch. Among the DEGs, we identified FveTCP9, homologous to AtBRC1, and genes involved in the phytohormone and flowering pathways. These genes were chosen for further analysis to investigate their role in the AxM fate.

In order to initiate a gene network, a second transcriptomic analysis included the spatio-temporal development of the axillary bud into a lateral branch or a stolon. Results highlighted the effects of the axillary bud position at the node of the primary crown and the developmental stage of the seedling on the transcriptome.

(3) The study of the chosen DEGs by using different approaches, qPCR in different genetic backgrounds and/or in situ hybridization, confirmed their role in controlling the AxM fate. Among these genes, the CRISPR-Cas9 mutation of FveTCP9 validates its role in the AXM fate and shows that lateral branches were produced at the expense of stolons.

This thesis initiated a regulatory network controlling the fate of MAx and also identified key genes that could be studied in octoploid strawberry for future agronomic applications.

Jury :

• Mrs Béatrice DENOYES-ROTHAN
  Ingénieure de recherche INRAE UMR BFP - Directrice de thèse
• M. Jérôme JOUBES
  CNRS, Laboratoire de biogenèse membranaire - Examinateur
• M. François PARCY
  Directeur de Recherche Laboratoire Physiologie Cellulaire et Végétale, Université Grenoble Alpes - Rapporteur
• Mrs Claire PÉRILLEUX
  Professeure University of Liège, InBioS-PhytoSYSTEM - Rapporteur