title: The build-up of osmotic stress responses within the growing root apex using kinematics and RNA-sequencing.
abstract: Molecular regulation of growth must include spatial and temporal coupling of cell production and cell expansion. The underlying mechanisms, especially under environmental challenge, remain obscure. Spatial patterns of cell processes make the root apex well suited to deciphering stress signaling pathways, and to investigating both processes. Kinematics and RNA-sequencing were used to analyze the immediate growth response of hydroponically grown Populus nigra cuttings submitted to osmotic stress. About 7400 genes and unannotated transcriptionally active regions were differentially expressed between the division and elongation zones. Following the onset of stress, growth decreased sharply, probably due to mechanical effects, before recovering partially. Stress impaired cell expansion over the apex, progressively shortened the elongation zone, and reduced the cell production rate. Changes in gene expression revealed that growth reduction was mediated by a shift in hormone homeostasis. Osmotic stress rapidly elicited auxin, ethylene, and abscisic acid. When growth restabilized, transcriptome remodeling became complex and zone specific, with the deployment of hormone signaling cascades, transcriptional regulators, and stress-responsive genes. Most transcriptional regulations fit growth reduction, but stress also promoted expression of some growth effectors, including aquaporins and expansins Together, osmotic stress interfered with growth by activating regulatory proteins rather than by repressing the machinery of expansive growth.
authors.affiliation: UMR EEF, INRA, Université de Lorraine, 54280 Champenoux, France.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Royer
authors.affiliation: UMR EEF, INRA, Université de Lorraine, 54280 Champenoux, France.
authors.forename: David
authors.initials: D
authors.lastname: Cohen
authors.affiliation: UMR EEF, INRA, Université de Lorraine, 54280 Champenoux, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Aubry
authors.affiliation: IGA Technology Services, I-33100 Udine, Italy.
authors.forename: Vera
authors.initials: V
authors.lastname: Vendramin
authors.affiliation: IGA Technology Services, I-33100 Udine, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Scalabrin
authors.affiliation: IGA Technology Services, I-33100 Udine, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Cattonaro
authors.affiliation: UMR EEF, INRA, Université de Lorraine, 54280 Champenoux, France triboulo@nancy.inra.fr.
authors.forename: Marie-Béatrice
authors.initials: MB
authors.lastname: Bogeat-Triboulot
authors.affiliation: UMR EEF, INRA, Université de Lorraine, 54280 Champenoux, France.
authors.forename: Irène
authors.initials: I
authors.lastname: Hummel
mesh_terms: D017360:Arabidopsis / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D001696:Biomechanical Phenomena / Q000502:physiology; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis; D009997:Osmotic Pressure / Q000502:physiology*; D018518:Plant Root Cap / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D017423:Sequence Analysis, RNA; D015398:Signal Transduction / Q000502:physiology
keywords: Division; Populus nigra; elongation; hormonal signaling; osmotic stress; root apical meristem; root growth; transcriptome