L’effet du stress thermique sur le contrôle génétique de la morphogenèse inflorescentielle chez Solanum lycopersicum

Details

Supervisors

Quinet, Muriel

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

enGlobal warming increases the frequency of moderate and prolonged heat waves, a condition known to disrupt tomato (Solanum lycopersicum) reproduction and potentially inflorescence architecture and flower production. Inflorescence morphogenesis relies on the transition and maintenance of inflorescence and floral meristematic identities, regulated by SFT (florigen), MC (AP1/FUL-like), and J (AGL24/SVP-like). This thesis, devoted to the effect of heat stress on the genetic control of inflorescence morphogenesis in Solanum lycopersicum, analyzes how heat destabilizes these regulations and their architectural and reproductive consequences. Three isogenic cultivar-mutant pairs (Platense/single flower truss (sft), Moneymaker/maccrocalyx (mc), Heinz/jointless (j)) were grown at 21°C (control) and 28°C (heat stress) under controlled conditions. Monitoring focused on vegetative growth, reproductive architecture (leaves and flowers per inflorescence), pollen production per flower, fruit set, fruit quality (weight, diameter, sugar content, seeds), as well as physiological and pigment measurements and semi-quantitative PCR expression. Overall, 28°C reveals genotype-dependent vegetative plasticity in our duos: some duos show a biomass cost under heat, while others remain dominated by the effect of the mutation, indicating that architecture genes modulate the source-sink balance and tolerance of growth phases. In terms of inflorescence architecture, heat accentuates vegetative reversion in mutants, particularly when the florigenic signal is weakened (sft). Conversely, j more often maintains dominant flower production and mc remains close to a balance between flowers and leaves, illustrating contrasting meristematic stabilities depending on the genotype. The reproductive phase is the most vulnerable to rising temperatures: the amount of pollen per anther and fruit production decrease for all genotypes, with cultivars showing greater resilience than mutants. Heat also reduces fruit size, while sugar content and number of seeds per fruit vary depending on the genotype. Physiological and pigment measurements are generally stable but reflect an accelerated leaf growth rate under heat. In conclusion, heat stress acts as a revealer of genotype-dependent weaknesses by destabilizing inflorescence morphogenesis and impairing flower fertility and fruit production. Stabilizing inflorescence and floral morphogenesis (SFT, MC, J) and pollen resilience appear to be priority adaptation levers.