Sucrose-responsive osmoregulation of plant cell size by a long non-coding RNA

In plants,sugars are the key source of energy and metabolic building blocks.The systemic transport of sugars is essential for plant growth and morphogenesis.Plants evolved intricate molecular networks to effectively distribute sugars.The dynamic distribution of these osmotically active compounds is a handy tool for regulating cell turgor pressure,an instructive force in developmental biology.In this study,we have investigated the molecular mechanism behind the dual role of the receptor-like kinase CANAR.We functionally characterized a long non-coding RNA,CARMA,as a negative regulator of CANAR.Sugarresponsive CARMA specifically fine-tunes CANAR expression in the phloem,the route of sugar transport.Our genetic,molecular,microscopy,and biophysical data suggest that the CARMA–CANAR module controls the shoot-to-root phloem transport of sugars,allows cells to flexibly adapt to the external osmolality by appropriate water uptake,and thus adjust the size of vascular cell types during organ growth and development.Our study identifies a nexus of plant vascular tissue formation with cell internal pressure monitoring,revealing a novel functional aspect of long non-coding RNAs in developmental biology.

A decoy receptor derived from alternative splicing fine-tunes cytokinin signaling in Arabidopsis

Hormone perception and signaling pathways have a fundamental regulatory function in the physiological processes of plants.Cytokinins,a class of plant hormones,regulate cell division and meristem maintenance.The cytokinin signaling pathway is well established in the model plant Arabidopsisthaliana.Several negative feedback mechanisms,tightly controlling cytokinin signaling output,have been described previously.In this study,we identified a new feedback mechanism executed through alternative splicing of the cytokinin receptor AHK4/CRE1.A novel splicing variant named CRE1int7 results from seventh intron retention,introducing a premature termination codon in the transcript.We showed that CRE1int7 is translated in planta into a truncated receptor lacking the C-terminal receiver domain essential for signal transduction.CRE1int7 can bind cytokinin but cannot activate the downstream cascade.We present a novel negative feedback mechanism of the cytokinin signaling pathway,facilitated by a decoy receptor that can inactivate canonical cytokinin receptors via dimerization and compete with them for ligand binding.Ensuring proper plant growth and development requires precise control of the cytokinin signaling pathway at several levels.CRE1int7 represents a so-far unknown mechanism for fine-tuning the cytokinin signaling pathway in Arabidopsis.