Isopentenyl phosphate kinase (IPK) is a recently discovered enzyme playing a key role in mevalonate pathway in isoprenoid biosynthesis, while systematic investigation of IPKs in plants is lack Here, through genome-wide identification and analysis of IPKs, we showed that IPKs gene are ubiquitously present in plant genomes. All IPKs protein previously identified had AAK (Amino Acid Kinase) domain. From 35 plant species with genome assembly data available, we extracted all AAK family members. Using OrthoMCL, we identified a group of 37 sequences in which Arabidopsis IPK protein was included. Further analysis showed that each peptide sequence in this group has a His residue which is a signature of IPK enzyme, indicating that the genes in this group were IPKs protein. Not like these in other domains of life which showed spotty distribution over the tree of life, virtually all plant genomes we analyzed here had IPK genes. Further, copy numbers of IPKs gene were very conserved in that no higher than 2 copies remained in each plant genome. Plant IPKs formed a distinctive clade in phylogenetic tree of plant AAK gene family, and had a phylogenetic topology conformed to that of plant species. Our results indicate IPK plays important roles in plant physiology and is conserved in plant evolution. The IPKs gene we identified here would provide new molecular targets for characterization of plant mevalonate pathway, and shed light on biochemistry of plant isoprenoids biosynthesis.
Ben Hu, Heng Yao, Yulong Gao, Ran Wang, Feng Li, Zefeng Li, Lifeng Jin and Yanxiang