CRK2 modulates flowering in Arabidopsis together with GLYCINE- RICH RNA BINDING PROTEIN 7 (GRP7)

Timely flowering is critical for the reproductive success of plants. Plants adjust flowering time through integration of multiple internal and environmental cues. A complex signalling system lies behind this integration, including multiple proteins like the GLYCINE-RICH RNA-BINDING PROTEIN 7 (GRP7), linked to the modulation of stress and flowering in Arabidopsis. Available data show the interaction between GRP7 and the receptor-like kinase CYSTEINE-RICH RECEPTOR-LIKE KINASE 2 (CRK2). Like GRP7, CRK2 plays multifaceted roles in the coordination of stress responses and development, but its role in development remains unclear. Phenotypic analyses of the crk2 and grp7-1 single mutants as well as the crk2/grp7-1 double mutant supported the interaction between CRK2 and GRP7. Moreover, exogenous gibberellic acid did not recover the rosette phenotype of crk2 mutants but as in sensitive plants, inhibited GA-biosynthesis transcripts. The pseudo insensitivity of crk2 mutant was recovered in the crk2/grp7-1 line pointing to a common role of CRK2 and GRP7 in the modulation of gibberellin signalling. Together, CRK2 and GRP7 integrate hormonal and spatial signals required for floral transition. These insights highlight a previously unrecognized layer of regulation in GA signalling and open new avenues to understand how membrane-localized kinases and RNA-binding proteins intersect to control developmental timing.