A single-cell morpho-transcriptomic map of brassinosteroid action in the Arabidopsis root

The effects of brassinosteroid signaling on shoot and root development have been characterized in great detail but a simple consistent positive or negative impact on a basic cellular parameter was not identified.In this study,we combined digital 3D single-cell shape analysis and single-cell mRNA sequencing to charac-terize root meristems and mature root segments of brassinosteroid-blind mutants and wild type.The resul-tant datasets demonstrate that brassinosteroid signaling affects neither cell volume nor cell proliferation capacity.Instead,brassinosteroid signaling is essential for the precise orientation of cell division planes and the extent and timing of anisotropic cell expansion.Moreover,we found that the cell-aligning effects of brassinosteroid signaling can propagate to normalize the anatomy of both adjacent and distant brassinosteroid-blind cells through non-cell-autonomous functions,which are sufficient to restore growth vigor.Finally,single-cell transcriptome data discern directly brassinosteroid-responsive genes from genes that can react non-cell-autonomously and highlight arabinogalactans as sentinels of brassinosteroid-dependent anisotropic cell expansion.

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.