AtSK11 and AtSK12 Mediate the Mild Osmotic Stress-Induced Root Growth Response in Arabidopsis

Int J Mol Sci. 2020 Jun 2;21(11):3991. doi: 10.3390/ijms21113991.

Abstract

Although most osmotic stresses are harmful to plant growth and development, certain drought- or polyethylene glycol (PEG)-induced mild osmotic stresses promote plant root growth. The underlying regulatory mechanisms of this response remain elusive. Here, we report that the GLYCOGEN SYNTHASE KINASE 3 (GSK3) genes ARABIDOPSIS THALIANA SHAGGY-RELATED KINASE 11 (AtSK11) (AT5G26751) and AtSK12 (AT3G05840) are involved in the mild osmotic stress (-0.4 MPa) response in Arabidopsis thaliana. When grown on plant medium infused with different concentrations of PEG to mimic osmotic stress, both wild-type (WT) and atsk11atsk12 plants showed stimulated root growth under mild osmotic stress (-0.4 MPa) but repressed root growth under relatively strong osmotic stress (-0.5, -0.6, -0.7 MPa) as compared to the mock condition (-0.25 MPa). The root growth stimulation of atsk11atsk12 was more sensitive to -0.4 MPa treatment than was that of WT, indicating that AtSK11 and AtSK12 inhibit the mild stress-induced root growth response. RNA-seq analysis of WT and atsk11atsk12 plants under three water potentials (-0.25 MPa, -0.4 MPa, -0.6 MPa) revealed 10 differentially expressed candidate genes mainly involved in cell wall homeostasis, which were regulated by AtSK11 and AtSK12 to regulate root growth in response to the mild stress condition (-0.4 MPa). Promoter motif and transcription factor binding analyses suggested that the basic helix-loop-helix (bHLH) transcription factor bHLH69/LJRHL1-LIKE 2 (LRL2) may directly regulate the expression of most -0.4 MPa-responsive genes. These findings indicate that mild osmotic stress (-0.4 MPa) promotes plant growth and that the GSK3 family kinase genes AtSK11 and AtSK12 play a negative role in the induction of root growth in response to mild osmotic stress.

Keywords: Arabidopsis thaliana; GSK3; osmotic stress; root growth; water potential.

MeSH terms

  • Arabidopsis / physiology*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / physiology*
  • Droughts
  • Gene Expression Regulation, Plant
  • Glycogen Synthase Kinase 3 / genetics
  • Glycogen Synthase Kinase 3 / physiology
  • Mannitol
  • Microscopy, Confocal
  • Osmoregulation
  • Osmotic Pressure*
  • Plant Roots / physiology*
  • Polyethylene Glycols / chemistry
  • Pressure
  • Promoter Regions, Genetic
  • Protein Kinases / genetics
  • Protein Kinases / physiology*
  • RNA-Seq

Substances

  • Arabidopsis Proteins
  • Mannitol
  • Polyethylene Glycols
  • Protein Kinases
  • ATSK12 protein, Arabidopsis
  • ATSK11 protein, Arabidopsis
  • Glycogen Synthase Kinase 3