Function of calcium-dependent protein kinase CPK28 of Arabidopsis thaliana in plant stem elongation and vascular development

Plant J. 2013 Mar;73(6):883-96. doi: 10.1111/tpj.12090. Epub 2013 Jan 15.


After a period of vegetative growth, plants undergo a developmental switch to the reproductive phase, inducing the transition to bolting, elongation of the inflorescence and flowering. We have identified calcium-dependent protein kinase CPK28 from Arabidopsis thaliana as a regulatory component that controls stem elongation and vascular development. In two independent mutant alleles of cpk28, a reduction of stem elongation, accompanied by shorter leaf petioles and enhanced anthocyanin levels, is observed upon the transition to the generative phase. Anatomical analysis revealed an altered vascular pattern characterised by fewer xylem tracheary elements but at the same time increased lignification and secondary growth. Coincident with these morphological changes, cpk28 mutants showed altered expression of NAC transcriptional regulators NST1 and NST3 as well as of GA3ox1, a key regulator of gibberellic acid homeostasis. In vitro protein kinase activity of CPK28 is strictly calcium-dependent. Furthermore, CPK28 is phosphorylated in vivo at several sites. Site-specific amino acid substitutions at these phosphorylation sites resulted in reduced in vitro activity. However, when introduced into a cpk28 mutant background, wild-type and phosphorylation site variants, but not kinase-inactive variants of CPK28 complemented the morphological and developmental defects. Our data identify CPK28 as a developmentally controlled regulator for coordinated stem elongation and secondary growth.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Anthocyanins / metabolism
  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Gene Expression Regulation, Plant
  • Gibberellins / metabolism
  • Lignin / metabolism
  • Molecular Sequence Data
  • Mutation
  • Phosphorylation
  • Plant Shoots / genetics
  • Plant Shoots / growth & development
  • Plant Stems / genetics
  • Plant Stems / growth & development*
  • Plant Stems / metabolism
  • Plants, Genetically Modified
  • Protein Kinases / genetics
  • Protein Kinases / metabolism
  • Transcription Factors / genetics
  • Xylem / anatomy & histology
  • Xylem / growth & development


  • Anthocyanins
  • Arabidopsis Proteins
  • Gibberellins
  • NST1 protein, Arabidopsis
  • NST3 protein, Arabidopsis
  • Transcription Factors
  • Lignin
  • gibberellic acid
  • Protein Kinases
  • calcium-dependent protein kinase