MAP-ping genomic organization and organ-specific expression profiles of poplar MAP kinases and MAP kinase kinases.
BACKGROUND
As in other eukaryotes, plant mitogen-activated protein kinase (MAPK) cascades are composed of three classes of hierarchically organized protein kinases, namely MAPKKKs, MAPKKs, and MAPKs. These modules rapidly amplify and transduce extracellular signals into various appropriate intracellular responses. While extensive work has been conducted on the post-translational regulation of specific MAPKKs and MAPKs in various plant species, there has been no systematic investigation of the genomic organization and transcriptional regulation of these genes.


RESULTS
Ten putative poplar MAPKK genes (PtMKKs) and 21 putative poplar MAPK genes (PtMPKs) have been identified and located within the poplar (Populus trichocarpa) genome. Analysis of exon-intron junctions and of intron phase inside the predicted coding region of each candidate gene has revealed high levels of conservation within and between phylogenetic groups. Expression profiles of all members of these two gene families were also analyzed in 17 different poplar organs, using gene-specific primers directed at the 3'-untranslated region of each candidate gene and real-time quantitative PCR. Most PtMKKs and PtMPKs were differentially expressed across this developmental series.


CONCLUSIONS
This analysis provides a complete survey of MAPKK and MAPK gene expression profiles in poplar, a large woody perennial plant, and thus complements the extensive expression profiling data available for the herbaceous annual Arabidopsis thaliana. The poplar genome is marked by extensive segmental and chromosomal duplications, and within both kinase families, some recently duplicated paralogous gene pairs often display markedly different patterns of expression, consistent with the rapid evolution of specialized protein functions in this highly adaptive species.
Nicole
Marie-Claude
MC
Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, Quebec, Quebec, Canada. MCNicole@cfl.forestry.ca
Hamel
Louis-Philippe
LP
Morency
Marie-Josée
MJ
Beaudoin
Nathalie
N
Ellis
Brian E
BE
Séguin
Armand
A
D020413:3' Untranslated Regions / Q000235:genetics; D032461:Chromosomes, Plant / Q000235:genetics; D005091:Exons / Q000235:genetics; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics*; D007438:Introns / Q000235:genetics; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics*; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics*; D008957:Models, Genetic; D010940:Plant Proteins / Q000235:genetics; D018514:Plant Structures / Q000201:enzymology / Q000235:genetics; D032107:Populus / Q000201:enzymology / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods
D020413:3' Untranslated Regions; D010940:Plant Proteins; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases