Friday, April 28, 2023 - Thesis defense - Gabriel Hoang

Gabriel Hoang

Team FDFE

Friday, April 28, 2023 - 2:00 pm - Colette and Josy Bové Amphitheater - Campus INRAE Villenave d'Ornon

Abstract :

Fruit yield is a major trait in fleshy fruit species and represents an important agronomic issue especially for tomato, Solanum lycopersicum. However, yield is a complex multigenic trait for which physiological determinism is not fully understood. In this context, my PhD work aimed to identify and characterize causal mutations responsible for alterations in both fruit development and yield following forward and reverse genetic approaches. First, I developed a forward genetic approach to identify causal mutations responsible for a yield-increase phenotype in two EMS mutants from a Micro-Tom collection, P17F7 and P22H3. Phenotyping of yield trait components in BC1F2 segregant populations associated to a mapping-by-sequencing strategy, combined with KASPar genotyping and bulk segregant analysis, allowed me to identify positives loci on chromosomes 04 and 08 linked with the yield increase phenotype in both mutants. In addition, a strong unfavourable locus was identified on chromosome 09 in P17F7. Candidate genes were identified for these loci. Yield analyses of recombinant BC1F3 individuals for candidate loci or generation of transgenic lines are now necessary to validate the causal mutations. In parallel, I performed the functional characterization of SlZFP2 transcription factor. Indeed, the knocked out of SlZFP2 by retrotransposon insertion was formerly shown to be responsible for a reduction of fruit size associated with an alteration of locular tissue. I showed that locular tissue morphogenesis alteration was due to both a drastic reduction in cell size and ploidy levels in ZFP2-CRISPR/Cas9 mutants. Expression studies by RT-qPCR revealed changes in cell cycle and endoreduplication genes expression and RNA-seq analyses allowed to propose a first list of SlZFP2 transcription factor potential direct targets.

Members of the jury :

Mme. LEMAIRE-CHAMLEY Martine Chargée de recherche, INRAE Bordeaux - Direction
M. JOUBES Jérome Professeur, Université de Bordeaux - Président
M. PIRRELLO Julien Maître de conférences, INP-ENSAT Toulouse
M. JIMENEZ-GOMEZ José Directeur de recherche, CBGP Madrid (Espagne) - Rapporteurs
Mme. SCHURDI-LEVRAUD Valérie Professeure, Université de Bordeaux
Mme. NELISSEN Hilde Group leader, VIB Ghent (Belgique) - Examinatrices
Mme. FERNANDEZ-LOCHU Lucie Chargée de recherche, INRAE Bordeaux - Invitée