A novel plant code optimization phosphomannose isomerase (pPMI) and its application in rice (Oryza sativa L.) transformation as selective marker

The phosphomannose isomerase (PMI) gene has been developed as selective marker gene for plant transformation. This positive selection system does not use toxic compounds such as antibiotics or herbicides. In this study, we used PMI effectively and safely. The original nucleotide sequence of PMI was codon optimized as rice (Oryza sativa L.) synonymous codon usage bias. The nucleotides in the PMI were optimized according to the preferred codons in rice. This plant code optimized phosphomannose isomerase (pPMI) has higher GC content (61.31%), especially GC content at the third position in a codon (83.42%). The vectors harboring pPMI and PMI were transferred into rice by Agrobacterium-mediated transformation. There were higher transformation frequency (54.5%) and single copy rate (44.5%) using pPMI as selective marker than PMI. This work showed that pPMI could be a suitable substitution for PMI in production of transgenic crops. Moreover, pPMI could be used in gene editing technology for higher transformation frequency and safety.