The seminars take place on the Montpellier Institut Agro/INRAE Campus of La Gaillarde (2, place P. Viala Montpellier)

Thursday, May 30 2023

Amphi 2 (Bât. 2bis)

Jean Colcombet

(IPS2, Paris-Saclay)

The MKK3 module integrates nitrate and light signals to modulate secondary dormancy

Seed dormancy is a momentary and reversible blockage of germination, even when conditions are favourable. Primary dormancy is established during seed maturation while secondary dormancy is set up on the free seed, following an exposure to unfavourable factors. Both dormancies are lifted over time or in response to environmental factors, such as light, nitrate and coldness. QTL analyses for viviparity identified MKK3 kinase in cereals as a major player in dormancy control. MKK3 belongs to the plant MAP2K family involved, together with MAP3K and MAPK families, in the constitution MAPK phosphorylation cascades. Here, we showed that MKK3 also plays a role in secondary dormancy in Arabidopsis, suggesting a conserved mechanism between mono- and di-cotyledons. We also identified the whole module which involves MAP3K13/14/19/20, MKK3 and clade-C MAPKs, including MPK7. Seeds impaired in this module acquired secondary dormancy more rapidly than WT seeds and this dormancy is less sensitive to nitrate, a signal ably to release dormancy. We also demonstrated that MPK7 was strongly activated in the seed during dormancy release, especially in response to light and nitrate. This activation was greatly reduced in map3k mutants. Finally, we showed that the module was not regulated, and apparently did not regulate, the ABA/GA hormone balance, one of the crucial mechanisms of seed dormancy control. Overall, our work identified a whole new MAPK module controlling seed germination and enlarged the panel of functions of the MKK3-related modules in plants.

Contact: Tou-Cheu Xiong

Contacts IBIP :

Sabine Zimmermann (sabine.zimmermann@cnrs.fr)

Alexandre Martiniere (alexandre.martiniere@cnrs.fr)

Aude Coupel-Ledru (aude.coupel-ledru@inrae.fr)

Chantal Baracco (chantal.baracco@inrae.fr)