Integrating flowering and stress responses in Arabidopsis through KH-domain genes

Plant reproductive success largely relies on flowering under favorable conditions. However, stress factors have forced plants to acquire adaptive strategies to coordinate floral timing and stress responses through key genetic elements. RNA-binding proteins with K-homology (KH) domains are emerging as versatile regulators of an increasing number of plant developmental processes, including flowering and stress acclimation. InArabidopsis thaliana,FLKandHOS5encode multifaceted KH-domain proteins associated with transcription and cotranscriptional operations.FLKfacilitates floral transition by repressingFLC, the central flowering inhibitor, while both KH-genes have been involved in abiotic stress and defense against pathogens. Our genetic and molecular data identify HOS5 as a novel flowering regulator that, together with FLK, repressesFLC. Our transcriptomics results reveal that, in addition,FLKandHOS5cooperatively repress numerous stress-responsive genes. Consistent with this,flk hos5double mutant plants exhibit elevated levels of stress-induced gene activities and enhanced resistance to abiotic stress and pathogenic fungi. The coordinated repression ofFLCand stress-induced genes by FLK and HOS5 suggests that these KH proteins are part of a cotranscriptional regulatory hub key for orchestrating flowering time and environmental adaptation responses.