Phylogenetic and comparative gene expression analysis of barley (Hordeum vulgare) WRKY transcription factor family reveals putatively retained functions between monocots and dicots.
BACKGROUND
WRKY proteins belong to the WRKY-GCM1 superfamily of zinc finger transcription factors that have been subject to a large plant-specific diversification. For the cereal crop barley (Hordeum vulgare), three different WRKY proteins have been characterized so far as regulators in sucrose signaling, pathogen defense, and in response to cold and drought. However, their phylogenetic relationship remained unresolved.


RESULTS
In this study, we used available sequence information to identify a minimum number of 45 barley WRKY transcription factor (HvWRKY) genes. According to their structural features, the HvWRKY factors were classified into the previously defined polyphyletic WRKY subgroups 1 to 3. Furthermore, we could assign putative orthologs of the HvWRKY proteins in Arabidopsis and rice. While in most cases clades of orthologous proteins were formed within each group or subgroup, other clades were composed of paralogous proteins for the grasses and Arabidopsis only, which is indicative of specific gene radiation events. To gain insight into their putative functions, we examined expression profiles of WRKY genes from publicly available microarray data resources and found group specific expression patterns. While putative orthologs of the HvWRKY transcription factors have been inferred from phylogenetic sequence analysis, we performed a comparative expression analysis of WRKY genes in Arabidopsis and barley. Indeed, highly correlative expression profiles were found between some of the putative orthologs.


CONCLUSIONS
HvWRKY genes have not only undergone radiation in monocot or dicot species, but exhibit evolutionary traits specific to grasses. HvWRKY proteins exhibited not only sequence similarities between orthologs with Arabidopsis, but also relatedness in their expression patterns. This correlative expression is indicative for a putative conserved function of related WRKY proteins in monocot and dicot species.
Mangelsen
Elke
E
Department of Plant Biology and Forest Genetics, The Swedish University of Agricultural Sciences (SLU), PO Box 7080, SE-750 07Uppsala, Sweden. elke.mangelsen@vbsg.slu.se
Kilian
Joachim
J
Berendzen
Kenneth W
KW
Kolukisaoglu
Uner H
UH
Harter
Klaus
K
Jansson
Christer
C
Wanke
Dierk
D
D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D019143:Evolution, Molecular; D015870:Gene Expression; D001467:Hordeum / Q000235:genetics*; D019684:Magnoliopsida / Q000235:genetics; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics*; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics*
D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; D010940:Plant Proteins; D014157:Transcription Factors