Determining the molecular mechanism underlying GA inhibition of flowering in apple tree

Date de mise à jour : 21 septembre 2021

Alternate bearing is a cyclical change in crop load intensity characterised by ‘on’ years, where many small fruits are produced, and ‘off’ years of low production. This fluctuation of yield and quality occurs in many tree species and impacts economic viability. Alternate bearing is related to changes in the levels of floral induction enabled in ‘on’ versus ‘off’ years (Guitton et al, 2016).

In the model plant species Arabidopsis thaliana, gibberellin (GA) promotes floral transition through suppressing DELLA proteins, which form complexes with transcription factors to affect the expression of several flowering-related genes. In contrast, floral induction is inhibited by GA in many woody perennial species. This inhibition appears associated with alternate bearing occurrence, but the mechanism is unknown. Using a range of molecular tools available for apple (Malus domestica), determination of the target genes of DELLA proteins and their interacting transcription factors will reveal a fuller picture of the mechanism preventing floral induction by GA.

In this project, the recruited student will contribute to decipher the mechanisms by which GA and DELLAs regulate floral induction in apple. To this end, he/she will use a protocol developed by the host lab for studying the function of apple transcription factors based on the glucocorticoid receptor (GR) system (Estevan et al, 2020; Falavigna et al, 2021). This protocol involves several steps, such as apple leaf genetic transformation, leaf-derived calli production, detection of GFP signal under fluorescence microscope and RT-qPCR analyses. Moreover, the candidate will test the effect of GA and the GA-inhibitor paclobutrazol on gene expression (RT-qPCR) and development on in vitro-grown apple plants.

The host lab is the AFEF team (https://umr-agap.cirad.fr/en/research/scientific-teams/fruit-tree-architecture-and-functions/) at the UMR AGAP Institute, in the CIRAD Lavalette Campus of Montpellier, France. At the end of the stage, the student will have the opportunity to apply for a fellowship to perform a PhD in the AFEF team.

Desired qualifications and skills

  • Master 1 on plant functional biology or related.
  • Good English level (oral and written).
  • High motivation and team work spirit.

Salary

~ 600 € / month

Bibliography

  • Guitton B, Kelner JJ, Celton JM, Sabau X, Renou JP, Chagné D, Costes E. 2016. Analysis of transcripts differentially expressed between fruited and deflowered ‘Gala’ adult trees: a contribution to biennial bearing understanding in apple. BMC Plant Biology. 16:55.
  • Estevan J, Gómez-Jiménez S, Falavigna VDS, Camuel A, Planel L, Costes E, Andrés F. An efficient protocol for functional studies of apple transcription factors using a glucocorticoid receptor fusion system. Appl Plant Sci. 2020 Oct 30;8(10):e11396.
  • Falavigna VDS, Severing E, Lai X, Estevan J, Farrera I, Hugouvieux V, Revers LF, Zubieta C, Coupland G, Costes E, Andrés F. 2021. Unraveling the role of MADS transcription factor complexes in apple tree dormancy. Accepted in New Phytologist.

Date de mise à jour : 21 septembre 2021