Post-translational modification of an R2R3-MYB transcription factor by a MAP Kinase during xylem development.
Despite the pivotal role played by R2R3-MYB family members in the regulation of plant gene expression, little is known about post-translational regulation of these proteins. In animals, the MYB family member, c-MYB, is post-translationally modified by a mitogen-activated protein kinase (MAPK), p42(mapk). In order to test the hypothesis that R2R3-MYB proteins may be regulated by MAPK activity, interplay between a R2R3-MYB family member expressed in differentiating pine xylem (Pinus taeda MYB4, PtMYB4) and MAPK proteins expressed in the same tissue was examined. One of the MAPK proteins expressed in pine xylem, PtMAPK6, phosphorylated PtMYB4. Recombinant PtMAPK6 phosphorylated PtMYB4 on serine-236, located in the C-terminal activation domain of this transcription factor in a context that is found in other plant MYB proteins. Modification of the PtMAPK6 target serine in PtMYB4 did not appear to alter DNA binding in vitro but did alter the ability of PtMYB4 to promote transcriptional activation in yeast. PtMAPK6 activity was detected in developing xylem cells that had ceased cell division and formed secondary walls. Together, the data support a role for PtMAPK6 during early xylem development and suggest a function for this kinase in regulating gene expression through phosphorylation of PtMYB4.
Morse
Alison M
AM
Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, FL 32610, USA.
Whetten
Ross W
RW
Department of Forestry and Environmental Resources, North Carolina State University, 5231 Jordan Hall, Box 8008, Raleigh, NC, 27695, USA.
Dubos
Christian
C
Centre for the Analysis of Genome Evolution & Function, Department of Cell & Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada, M5S 3B2.
Campbell
Malcolm M
MM
Centre for the Analysis of Genome Evolution & Function, Department of Cell & Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada, M5S 3B2.
D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics*; D010766:Phosphorylation; D041603:Pinus taeda / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000235:genetics*; D012694:Serine; D014157:Transcription Factors / Q000235:genetics*; D052584:Xylem / Q000235:genetics* / Q000254:growth & development
D014157:Transcription Factors; D012694:Serine; D020928:Mitogen-Activated Protein Kinases