In Silico Identification and Evolutionary Analysis of Plant <Emphasis Type="Italic">MAPKK6s</Emphasis>

Mitogen-activated protein kinase (MAPK) cascades are universal signal transduction modules in plants. Linking upstream MAPK kinase kinase (MAPKKK) to downstream MAPK, MAPK kinase (MAPKK) plays a crucial role in MAPK cascade. MAPKK6 is one member of the MAPKK family. In this study, we have found that plant MAPKK6 genes are widely distributed in different plant species, including moss, seedless vascular plants, gymnosperms, and angiosperms. However, no MAPKK6 can be found in genomes of algae. Analysis of exon–intron organization and intron phase showed that plant MAPKK6s are highly conserved genes during plant evolution. In Physcomitrella patens, Selaginella moellendorffii, and Picea glauca, MAPKK6s exist as multicopy genes. In most high plants, however, MAPKK6s exist as single-copy. Phylogenetic analysis indicated that the occurrence of single-copy of MAPKK6s in high plants is likely because of genomic copy-number loss.