Séminaire interne
Jeudi 9 février à 14h00 Amphi 206 (Cœur d’École)

Justine Drouault
Supervisors : Boris Parent, Randall Wisser
Team : MAGE, LEPSE

Reconsidering photoperiod-sensitivity for maize adaptation to climate change 

Flowering time is fundamental to the local adaptation and productivity of crop species. The timing of flowering is determined by rates of development and phase transitions, which are controlled by integrated networks of external (environment) and internal (plant) signals. Domesticated maize, originating from a tropical teosinte (Z. mays ssp. parviglumus), was spread globally by adapting its flowering time to novel environments. Tropical maize varieties require a short-day/long-night cycle for reproductive transition, while long-day conditions prolong this transition, giving rise to photoperiod sensitivity (PS). Elimination of PS enabled the adaptation of maize to long-day growing seasons in the temperate zone, such that temperature has become the main driver for flowering time in temperate varieties. Thus, historical selection has reshaped the phenotypic space for flowering time regulation in maize. In the context of global warming, where rising temperatures will hasten flowering times, maize yields are projected to decline. Reintroducing partial PS in temperate breeding pools could counteract these effects and expand the phenotypic space for adapting maize to climate change. To exploit the potential of PS, the ecophysiological response of flowering time across field environments has to be better understood. New knowledge is needed about variation in the physiological reaction norm for flowering time, the effects of PS alleles in temperate genetic backgrounds, and whether there is broad scale potential for PS as a novel climate adaptation.

Meijie Li
Supervisor: Christian Dubos
Team: Feros, IPSIM

Study of the molecular mechanisms that control iron-mobilizing coumarin biosynthesis, trafficking and storage

Iron (Fe) is essential for most living organisms. Although Fe is one of the most abundant elements found in soil, it is generally poorly available to plants since it is mainly present in the form of insoluble Fe (hydr)oxides. This is for instance the case in calcareous soils that represent one-third of the world’s cultivated lands. To cope with this poor bioavailability, non-grass species have evolved a reduction-based mechanism to mine Fe from the soil. Recently it has emerged that the secretion of Fe-mobilizing coumarins by the plant roots (via the PDR9 transporter) plays an important role in this process. Within the frame of my PhD thesis, I am characterizing another transporter we identified (PDR9-like) potentially involved in catechol coumarin secretion with PDR9. I am also studying the post-translational regulation of PDR9 activity (phosphorylation and ubiquitination) based on data obtained using targeted proteomic (LC-MS/MS). For this purpose, pdr9 transgenic lines expressing various mutated version of PDR9 expressed under its own promoter, and fused to the m-Citrine reporter protein, have been generated and will be characterized (complementation and protein localization). Last, I will search novel genes potentially involved in catechol coumarins biosynthesis, trafficking and storage by using untargeted approaches (i.e. GWAS, transcriptomic or proteomic).